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Increasing heatwaves are threatening forest ecosystems globally. Leaf thermal regulation and tolerance are important for plant survival during heatwaves, though the interaction between these processes and water availability is unclear. Genotypes of the widely distributed foundation tree species Populus fremontii were studied in a controlled common garden during a record summer heatwave-where air temperature exceeded 48 °C. When water was not limiting, all genotypes cooled leaves 2 to 5 °C below air temperatures. Homeothermic cooling was disrupted for weeks following a 72-h reduction in soil water, resulting in leaf temperatures rising 3 °C above air temperature and 1.3 °C above leaf thresholds for physiological damage, despite the water stress having little effect on leaf water potentials. Tradeoffs between leaf thermal safety and hydraulic safety emerged but, regardless of water use strategy, all genotypes experienced significant leaf mortality following water stress. Genotypes from warmer climates showed greater leaf cooling and less leaf mortality after water stress in comparison with genotypes from cooler climates. These results illustrate how brief soil water limitation disrupts leaf thermal regulation and potentially compromises plant survival during extreme heatwaves, thus providing insight into future scenarios in which ecosystems will be challenged with extreme heat and unreliable soil water access.

Heat stress poses a significant threat to grain yield. As an α2 subunit of the 26S proteasome, TT1 has been shown to act as a critical regulator of rice heat tolerance. However, the heat tolerance mechanisms mediated by TT1 remain elusive. In this study, we unveiled that small ubiquitin-like modifier (SUMO)-conjugating enzyme 1 (SCE1), which interacts with TT1 and acts as a downstream component of TT1, is engaged in TT1-mediated 26S proteasome degradation. We showed that SCE1 functions as a negative regulator of heat tolerance in rice, which is associated with its ubiquitination modification. Furthermore, we observed that small heat-shock proteins (sHSPs) such as Hsp24.1 and Hsp40 can undergo SUMOylation mediated by SCE1, leading to increased accumulation of sHSPs in the absence of SCE1. Reducing protein levels of SCE1 significantly enhanced grain yield under high-temperature stress by improving seed-setting rate and rice grain filling capacity. Taken together, these results uncover the critical role of SCE1 in the TT1-mediated heat tolerance pathway by regulating the abundance of sHSPs and SUMOylation, and ultimately modulating rice heat tolerance. These findings underscore the great potential of the TT1–SCE1 module in improving the heat tolerance of crops. This study reveals the pivotal role of SCE1, a SUMO E2 enzyme in TT1-mediated thermotolerance by modulating the abundance of small heat-shock proteins and SUMO modification. The findings implicate the great potential of the TT1–SCE1 module in integrating ubiquitination and SUMOylation, thereby serving as a valuable genetic target for enhancing heat tolerance in crops. [ABSTRACT FROM AUTHOR]

In India, mung bean [Vigna radiata (L.) R. Wilczek] is 3rd most important legume crop among pulses after chickpea and pigeon pea that grows most efficiently at temperatures between 27 and 35°C. It is thermotolerant during vegetative phase however sensitive to heat stress during reproductive stage. Terminal high temperature (>40°C) during the summers significantly reduces grain yield of mung bean by decreasing photosynthesis, growth, biomass production, pollen viability, grain setting & pod filling and impairing source sink balance and accelerating flowers and pods shedding. Analysis of the genetic variations in the accessible germplasm and the physio-biochemical processes involve in modulating heat sensitivity and tolerance have prime importance for enhancing the grain yield of mung bean. There is great scope to improve the heat tolerance and yield of mung bean by using various long-term and short-term strategies. In this article, physiological and molecular responses along with mitigation strategies in relation to improve thermotolerance in mung bean have been reviewed. [ABSTRACT FROM AUTHOR]

BACKGROUND: High‐temperature (HT) stress significantly affects the quality of rice (Oryza sativa L.), although the underlying the mechanism remains unknown. Therefore, in the present study, we assessed protein components, amino acids, mineral element levels, starch biosynthesis enzyme activity and gene expression of two heat‐sensitive and two heat‐tolerant genotypes under HT treatment during early (from 1 to 10 days, T1) and mid‐filling (from 11 to 20 days, T2) after anthesis. RESULTS: Except for one cultivar, most rice varieties exhibited increased levels of amylose, chalky degree and protein content, along with elevated cracked grains and pasting temperatures and, consequently, suppressed amino acid levels under HT stress. HT treatment also increased protein components, macro‐ (Mg, K, P and S) and microelements (Cu, Zn, and Mo) in the rice flour. Both HT treatments reduced the activity of ADP‐glucose pyrophosphate, ground‐bound starch synthase, as well as the relative ratio of amylose to total starch, at the same time increasing starch branch enzyme activity. The expression levels of OsAGPL2, OsSSS1 and OsSBE1 in all varieties exhibited the same trends as enzyme activity under HT treatment. CONCLUSION: High temperatures negatively affected rice quality during grain filling, which is related to heat tolerance and grain shape. Altered enzymatic activity is crucial to compensate for the lowered enzyme quality under heat stress. © 2024 Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

High ambient temperature and relative humidity significantly affect growth and production performance in poultry. Ability of poultry to regulate their core body temperature relative to the ambient temperature depends on the relative nutrient/energy expenditure in maintenance and performance requirements. We hypothesized that changes in rectal temperature corrected for surface area can be used as a measure of heat tolerance/sensitivity. Rectal temperatures of one hundred mixed sex Ross 308 broiler chickens were measured hourly from 6 AM to 6 PM at 24 days of age. The ambient temperature and relative humidity were also measured hourly for the same 12-h period. Body weights were measured at day 24 and 38 days of age. The temperature-humidity index (THI) increased from 77.5 at 6.00 AM and peaked at 83.5 at 3.00 PM. The average rectal temperature increased from 39.900C at 6.00 AM to about 41.300C at 9.00 AM. Thereafter, the average rectal temperature remained constant until 3.00 PM when it began to decline. At 6.00 PM, the rectal temperature had declined to about 40.70 °C. Evaporative heat loss is affected by surface areas and as a result, rectal temperature was corrected for surface area. The change in rectal temperature corrected for surface area was negatively correlated with body weight gain indicating variability in the response of individual chickens exposed to similar THI. This variability was attributed to heat tolerance. It was hypothesized that mismatch between nutrient and energy supply and the partition of nutrient/energy between maintenance of core body temperature and protein synthesis could be reflected on the differences in heat-tolerance and body weight gain in the chicken population. The genetic basis of differences in rectal temperature changes corrected for surface area could be elucidated as a means of developing thermo-tolerant chickens. [ABSTRACT FROM AUTHOR]

Due to the rise in global temperatures with climate change, insects, as ectotherms, critically depend on their heat tolerance for survival and reproduction. Heat shock proteins (HSPs) are essential for heat tolerance by averting protein denaturation; however, whether HSPs contribute to reproduction‐related heat tolerance remains largely unexplored. The study investigated the reproductive heat tolerance and recovery of Monochamus alternatus, a major forestry pest, in response to heat stress. Alongside impairing the development and viability of reproductive organs and sperm, heat stress was also found to reduce fecundity, fertility, mating, and oviposition behaviors. Remarkably, all reproductive parameters of M. alternatus recovered within 4 weeks postexposure. To investigate the recovery mechanisms, we identified 10 reproduction‐related proteins as candidate substrate proteins of an HSP protein in M. alternatus using immunoprecipitation coupled with mass spectrometry analysis. Heat stress inhibited the transcription of these reproduction‐related genes, thereby adversely affecting reproductive parameters. However, the induction of HSP20s transcription in response to heat stress appeared to facilitate the refolding of these critical reproduction‐related proteins during the recovery phase, thus preventing lasting reproductive damage. Overall, this study suggests that while M. alternatus populations might be vulnerable to climate‐induced temperature increases, their fertility can recover, mediated by the interaction of HSPs with reproduction‐related genes. These findings offer profound insights into insect heat tolerance and recovery, expanding our understanding of HSP20 proteins’ biological functions. [ABSTRACT FROM AUTHOR]

High temperature limit crop productivity as a consequence of global warming and climate change. In particular, high temperature interferes with sexual reproduction and thus fruit and seed formation in crops. In the present study, phenotypic evaluation of a tomato population, including 21 tomato genotypes, was carried out under high-temperature stress (35°C). Several reproductive and yield-related traits, including the number of inflorescences, number of flowers per inflorescence, pollen viability, fruit set, number of fruits per plant, and number of fruits per inflorescence, were investigated. Significant positive correlations between pollen viability and fruit set were observed (r = 0.83). Based on the obtained findings, the fruit set, pollen viability, number of fruits per plant, and number of fruits per inflorescence were recognized as markers for heat tolerance screening of tomato genotypes. These traits effectively separate tolerant and sensitive genotypes, which can be used in breeding program. At the same time, the number of inflorescences and the number of flowers per inflorescence did not separate between tolerant and sensitive genotypes. In conclusion, heat stress, through influencing pollen viability and fertilization, imposes its effects on reproductive organ development in tomato genotypes. [ABSTRACT FROM AUTHOR]

Summary The growth and development of maize (Zea mays L.) are significantly impeded by prolonged exposure to high temperatures. Heat stress transcription factors (HSFs) play crucial roles in enabling plants to detect and respond to elevated temperatures. However, the genetic mechanisms underlying the responses of HSFs to heat stress in maize remain unclear. Thus, we aimed to investigate the role of ZmHSFA2B in regulating heat tolerance in maize. Here, we report that ZmHSFA2B has two splicing variants, ZmHSFA2B‐I and ZmHSFA2B‐II. ZmHSFA2B‐I encodes full‐length ZmHSFA2B (ZmHSFA2B‐I), whereas ZmHSFA2B‐II encodes a truncated ZmHSFA2B (ZmHSFA2B‐II). Overexpression of ZmHSFA2B‐I improved heat tolerance in maize and Arabidopsis thaliana, but it also resulted in growth retardation as a side effect. RNA‐sequencing and CUT&Tag analyses identified ZmMBR1 as a putative target of ZmHSFA2B‐I. Overexpression of ZmMBR1 also enhanced heat tolerance in Arabidopsis. ZmHSFA2B‐II was primarily synthesized in response to heat stress and competitively interacted with ZmHSFA2B‐I. This interaction consequently reduced the DNA‐binding activities of ZmHSFA2B‐I homodimers to the promoter of ZmMBR1. Subsequent investigations indicate that ZmHSFA2B‐II limits the transactivation and tempers the function of ZmHSFA2B‐I, thereby reducing the adverse effects of excessive ZmHSFA2B‐I accumulation. Based on these observations, we propose that the alternative splicing of ZmHSFA2B generates a self‐regulatory loop that fine‐tunes heat stress response in maize. [ABSTRACT FROM AUTHOR]

Aim: Global warming has highlighted the importance of understanding the role of thermal tolerance as a driver of species distributions, especially for ectotherms. Here we analyse interactions between latitude, elevation and arboreality as predictors of geographic patterns of thermal tolerance in ants. Location: The collected data are distributed globally. Methods: We first tested the effect of latitude, elevation and its interactive effect on ant CTmax and CTmin. Second, we tested whether CTmax and CTmin are phylogenetic clustering. Finally, we tested whether CTmax and CTmin can be explained by nesting microhabitat (ground vs. tree‐nesting species) and whether the probability of occurrence of tree‐nesting species along thermal gradients helps explain the global pattern in ant CTmax. Results: CTmax and CTmin displayed high and low phylogenetic signals respectively and therefore showed different responses to geographic gradients. Notably, we found that CTmax was higher in higher latitudes. This was explained by a lack of elevational turnover at high latitudes among tree‐nesting species, which are exposed to warmer microclimates and have higher CTmax compared with ground‐nesting species. CTmin decreased with elevation at low latitudes, but did not vary with elevation at higher latitudes. Main Conclusions: Our findings highlight the important influence of arboreality on the macroecology of thermal tolerance, substantially modifying traditional notions of variation along latitudinal and elevation gradients. [ABSTRACT FROM AUTHOR]

Tropical rainforests are hot and may be particularly sensitive to ongoing anthropogenic global warming. This has led to increased interest in the thermotolerance of tropical trees. Thermotolerance of leaves of two tropical tree species, Terminalia catappa and Coccoloba uvifera, was determined by exposing leaf samples to 15‐min heat treatments, followed by measurements of potential photosystem II quantum yield (dark‐adapted value of variable/maximum chlorophyll a fluorescence, Fv/Fm) after 24 h and 14 days, and visible damage (necrosis) after 14 days. T50 (24 h), the temperature at which Fv/Fm declined by 50% 24 h after heat treatments, was associated with only ~10% leaf area damage in C. uvifera and no damage in T. catappa. In neither species was leaf necrosis observed at T5 (24 h), the temperature at which Fv/Fm declined by 5%. In both species, temperatures significantly higher than T50 (24 h) were required for 50% leaf area necrosis to occur. T50 (14 days) was a better proxy of visible leaf damage than T50 (24 h). The relationship between heat‐induced Fv/Fm decline and tissue necrosis varies among species. In species surveys of leaf thermal tolerances, calibration of the Fv/Fm assay against the necrosis test is recommended for each species under investigation. Fv/Fm measurements soon after heat exposure do not reliably predict irreversible heat damage and may thus not be suitable to model and predict the thermostability of tropical forest trees. [ABSTRACT FROM AUTHOR]

ABSTRACT Genomic selection (GS) and genome‐wide association studies (GWAS) have not been investigated in Vietnamese dairy cattle, even for basic milk production traits, largely due to the scarcity of individual phenotype recording in smallholder dairy farms (SDFs). This study aimed to estimate heritability (h2) and test the applicability of GS and GWAS for milk production, body conformation and novel heat tolerance traits using single test day phenotypic data. Thirty‐two SDFs located in either the north (a lowland vs. a highland) or the south (a lowland vs. a highland) of Vietnam were each visited for an afternoon and the next morning to collect phenotype data of all lactating cows (n = 345). Tail hair from each cow was sampled for subsequent genotyping with a 50K SNP chip at that same visit. Milk production traits (single‐test day) were milk yield (MILK, kg/cow/day), energy corrected milk yield adjusted for body weight (ECMbw, kg/100 kg BW/day), fat (mFA, %), protein (mPR, %) and dry matter (mDM, %). Conformation traits were body weight (BW, kg) and body condition score (BCS, 1 = thin to 5 = obese). Heat tolerance traits were panting score (PS, 0 = normal to 4.5 = extremely heat‐stressed) and infrared temperatures (IRTs, °C) at 11 areas on the external body surface of the cow (inner vulval lip, outer vulval surface, inner tail base surface, ocular area, muzzle, armpit area, paralumbar fossa area, fore udder, rear udder, forehoof and hind hoof), assessed by an Infrared Camera. Univariate linear mixed models and a 10‐fold cross‐validation approach were applied for GS. Univariate single SNP mixed linear models were applied for the GWAS. Estimated h2 (using the genotype information to build relationships among animals) were moderate (0.20–0.37) for ECMbw, mFA, mPR, mRE, BW, BCS and IRT at rear udder; low (0.08–0.19) for PS and other IRTs; and very low (≤ 0.07) for MILK, ECM and mDM. Accuracy of genomic estimated breeding values (GEBVs) was low (≤ 0.12) for MILK, ECM, mDM and IRT at hind hoof; and moderate to high (0.32–0.46) for all other traits. The most significant regions on chromosomes (BTA) associated with milk production traits were 0.47–1.18 Mb on BTA14. Moderate to high h2 and moderate accuracies of GEBVs for mFA, mPR, ECMbw, BCS, BW, PS and IRTs at rear udder and outer vulval surface suggested that GS using single test day phenotypic data could be applied for these traits. However, a greater sample size is required to decrease the bias of GEBVs by GS and increase the power of detecting significant quantitative trait loci (QTLs) by GWAS. [ABSTRACT FROM AUTHOR]

Simple Summary: Environmental indices are commonly used for detecting heat stress in dairy cattle; however, most studies have only focused on the productivity traits of dairy cattle in response to heat stress and have not considered their health and reproductive characteristics simultaneously. In this study, we aimed to determine the effects of heat stress on the production and reproduction performances of Thai–Holstein dairy cattle and the impact of the genetics of dairy cattle on their heat tolerance. We observed that heat stress significantly reduced milk yield and negatively affected the milk fat-to-protein ratio. Additionally, conception rates declined under heat stress, highlighting the challenges of finding an effective genetic approach for hot and humid regions, including Thailand. Genetic analysis revealed differences in heat tolerance among cows, indicating that the genetic improvement approach used in this study is suitable for planning future genetic improvements in dairy cattle. Heat stress severely affects dairy cattle production and reproduction performances in tropical regions. Genetic selection to maintain adequate yield and reproductive performance while enhancing their ability to withstand heat is essential for improving the genetics of dairy cows. Therefore, in this study, we aimed to estimate genetic parameters affecting production and reproduction performances under heat stress conditions in dairy cattle and to investigate the threshold point of heat stress for milk yield (MY), milk fat-to-protein ratio (FPR), and conception rate (CR) in Thai–Holstein dairy cattle. The data included 168,124 records related to MY and milk FPR and 21,278 records of CR in Thai–Holstein dairy cattle, covering the period from 1990 to 2007. A multiple-trait threshold-linear random regression model based on a Bayesian approach via Gibbs sampling was used to estimate variance components, genetic parameters (heritability values, and genetic correlations), and decline rates for each studied trait. The threshold point of heat stress was identified as a temperature and humidity index (THI) of 76. At THI76, a decline was observed in the MY, milk FPR, and CR of Thai dairy cattle. The heritability estimates for MY, milk FPR and CR were 0.347 ± 0.032, 0.293 ± 0.021, and 0.032 ± 0.001, respectively. The genetic correlation between MY and milk FPR and MY and CR were −0.24 and −0.53, respectively, whereas those between milk FPR and heat tolerance as well as between CR and heat tolerance were −0.48 and −0.49, respectively. In addition, the decline rates in MY, milk FPR, and CR were found to be associated with a high percentage of Holstein genetics. In conclusion, the results obtained in this study reveal that the simultaneous consideration of the MY, milk FPR, CR, and heat tolerance traits of Thai–Holstein dairy cattle is possible. In addition, developing a genetic model that incorporates THI is essential for sustainably addressing heat stress problems. [ABSTRACT FROM AUTHOR]

High-temperature stress (HTS) affects the growth and production of vegetable crops, including eggplant (Solanum melongena L.). Jasmonic acid (JA) plays key roles in regulating resistance to biotic and abiotic stresses in plants. Nonetheless, reports on the role of JA in heat tolerance in eggplant are rare. Herein, the effects of JA on heat tolerance in eggplant and the functions of the JA biosynthetic genes SmLOX4 and SmLOX5 were analyzed. The results showed that the JA content increased under high-temperature treatment (HTT) and exogenous methyl jasmonate (MeJA) treatment reduced the damage caused by HTT to eggplant. The expression of SmLOX4 and SmLOX5 was induced by HTT and significantly positively correlated with JA biosynthesis. SmLOX4 and SmLOX5 were localized in chloroplasts. The silencing of SmLOX4 and SmLOX5 by virus-induced gene silencing suppressed the heat tolerance of eggplant, whereas the overexpression of SmLOX4 and SmLOX5 enhanced the heat tolerance of Arabidopsis thaliana. JA content and the expression of JA signaling–related genes decreased in the SmLOX4 - and SmLOX5 -silenced plants but increased in the OE- SmLOX4 and OE- SmLOX5 transgenic plants. These results revealed that SmLOX4 and SmLOX5 improved eggplant heat tolerance by mediating JA biosynthesis and JA signaling pathways. [ABSTRACT FROM AUTHOR]

To analyze the heat tolerance of japonica rice in Liaohe plain rice-growing region, and establish an effective evaluation system of heat tolerance, 20 main varieties of japonica rice suitable for cultivating over this region were selected and planted under simulated temperature increase using the free air temperature increase system. The heat tolerance of different japonica rice varieties was comprehensively evaluated by multivariate statistical analysis methods based on the heat tolerance coefficients of 10 rice trait indicators, the effective panicle number (X1), grain number per spike (X2), seed setting rate (X3), 1000-grain weight (X4), yield (X5), brown rice rate (X6), milled rice rate (X7), protein content (X8), amylose content (X9), and taste value (X10) after harvesting and air-drying the rice. The results showed that the trait indicators except taste value were significantly or extremely reduced under the warming. Correlation analysis based on heat tolerance coefficients revealed different degrees of association between rice trait indicators. Principal component analysis condensed the 10 individual indicators into 4 mutually independent comprehensive indicators. The 4 comprehensive indicators had contribution rates of 34.816%, 19.265%, 15.636%, and 10.605%, respectively, giving a cumulative contribution rate of 80.322%. The comprehensive evaluation values of heat tolerance (Di value) were calculated using the membership function method. The higher the Di value, the stronger the heat tolerance. The heat tolerance of 'Yanjing 456' was the strongest and that of 'Shennong 016' was the worst. The 20 japonica rice varieties were classified into three categories based on their heat tolerance: the first category comprised 7 heat-tolerant varieties, the second category included 6 moderately heat-tolerant varieties, and the third category consisted of 7 heat-sensitive varieties. [ABSTRACT FROM AUTHOR]

Chickpea is one of the economically important legume crops adapted for winter season production in tropical climates. This study evaluated the physiological, morphological, and biochemical traits of eight Kabuli chickpea genotypes in an Australian tropical environment. The result revealed significant differences between genotypes for seed emergence, plant height, primary shoots, leaf number, leaf area index, gas-exchange parameters, seed yield, carbon discrimination (Δ13C), and natural abundance for nitrogen fixation. Among the tested genotypes, AVTCPK#6 and AVTCPK#19 exhibited late flowering (60–66 days) and late maturity (105–107 days), and had higher leaf photosynthetic rate (Asat) (28.4–31.2 µmol m−2 s−1), lower stomatal conductance (gsw) (516–756 mmol m−2 s−1), were associated with reduced transpiration rate (T) (12.3–14.5 mmol m−2 s−1), offered greater intrinsic water-use efficiency (iWUE) (2.1–2.3 µmol m−2 s−1/mmol m−2 s−1), and contributed a higher seed yield (626–746 g/m2) compared to other genotypes. However, a larger seed test weight (>60 g/100 seed) was observed for AVTCPK#24, AVTCPK#8, and AVTCPK#3. Similarly, a high proportion (45%) of larger seeds (>10–11 mm) was recorded for AVTCPK#24. Furthermore, a higher %Ndfa in AVTCPK#6 (71%) followed by AVTCPK#19 (63%) indicated greater symbiotic nitrogen fixation in high-yielding genotypes. Positive correlation was observed between %Ndfa and seed protein, as well as between seed yield and plant height, primary shoots, leaf count, leaf area index, leaf photosynthesis, stomatal conductance, transpiration rate at pod filling stage, biomass, and harvest index. An inverse correlation between (Δ13C) and iWUE, particularly in AVTCPK#6 and AVTCPK#19, indicates greater heat and drought tolerance, required for high-yielding Kabuli chickpea production in northern Australia. [ABSTRACT FROM AUTHOR]

Heat stress at the flowering stage significantly impacts rice grain yield, yet the number of identified genes associated with rice heat tolerance at this crucial stage remains limited. This study focuses on elucidating the function of the heat‐induced gene reduced heat stress tolerance 1 (OsRHS). Overexpression of OsRHS leads to reduced heat tolerance, while RNAi silencing or knockout of OsRHS enhances heat tolerance without compromising yield, as assessed by the seed setting rate. OsRHS is localized in the cytoplasm and mainly expressed in the glume and anther of spikelet. Moreover, OsRHS was found to interact with the HSP protein cHSP70‐4, and the knockout of cHSP70‐4 resulted in increased heat tolerance. Complementation assays revealed that the knockout of cHSP70‐4 could restore the compromised heat tolerance in OsRHS overexpression plants. Additional investigation reveals that elevated temperatures can amplify the bond between OsRHS and cHSP70‐4 within rice. Furthermore, our findings indicate that under heat stress conditions during the flowering stage, OsRHS plays a negative regulatory role in the expression of many stress‐related genes. These findings unveil the crucial involvement of OsRHS and cHSP70‐4 in modulating heat tolerance in rice and identify novel target genes for enhancing heat resilience during the flowering phase in rice. Summary statement: Our results demonstrate that the novel protein OsRHS serves as a negative regulator of rice heat tolerance during the flowering stage by interacting with the HSP70 protein cHSP70‐4 which also exerts a negative influence on rice heat tolerance, and the interaction between OsRHS and cHSP70‐4 is strengthened under heat stress conditions. [ABSTRACT FROM AUTHOR]

Abstract Birds maintain some of the highest body temperatures among endothermic animals. Often deemed a selective advantage for heat tolerance, high body temperatures also limits birds’ thermal safety margin before reaching lethal levels. Recent modelling suggests that sustained effort in Arctic birds might be restricted at mild air temperatures, which may require reductions in activity to avoid overheating, with expected negative impacts on reproductive performance. We measured within-individual changes in body temperature in calm birds and then in response to an experimental increase in activity in an outdoor captive population of Arctic, cold-specialised snow buntings (Plectrophenax nivalis), exposed to naturally varying air temperatures (− 15 to 36 °C). Calm buntings exhibited a modal body temperature range from 39.9 to 42.6 °C. However, we detected a significant increase in body temperature within minutes of shifting calm birds to active flight, with strong evidence for a positive effect of air temperature on body temperature (slope = 0.04 °C/ °C). Importantly, by an ambient temperature of 9 °C, flying buntings were already generating body temperatures ≥ 45 °C, approaching the upper thermal limits of organismal performance (45–47 °C). With known limited evaporative heat dissipation capacities in these birds, our results support the recent prediction that free-living buntings operating at maximal sustainable rates will increasingly need to rely on behavioural thermoregulatory strategies to regulate body temperature, to the detriment of nestling growth and survival.

Adaptation of reef-building corals to global warming depends upon standing heritable variation in tolerance traits upon which selection can act. Yet limited knowledge exists on heat-tolerance variation among conspecific individuals separated by metres to hundreds of kilometres. Here, we performed standardized acute heat-stress assays to quantify the thermal tolerance traits of 709 colonies of Acropora spathulata from 13 reefs spanning 1060 km (9.5° latitude) of the Great Barrier Reef. Thermal thresholds for photochemical efficiency and chlorophyll retention varied considerably among individual colonies both among reefs (approximately 6°C) and within reefs (approximately 3°C). Although tolerance rankings of colonies varied between traits, the most heat-tolerant corals (i.e. top 25% of each trait) were found at virtually all reefs, indicating widespread phenotypic variation. Reef-scale environmental predictors explained 12–62% of trait variation. Corals exposed to high thermal averages and recent thermal stress exhibited the greatest photochemical performance, probably reflecting local adaptation and stress pre-acclimatization, and the lowest chlorophyll retention suggesting stress pre-sensitization. Importantly, heat tolerance relative to local summer temperatures was the greatest on higher latitude reefs suggestive of higher adaptive potential. These results can be used to identify naturally tolerant coral populations and individuals for conservation and restoration applications. [ABSTRACT FROM AUTHOR]

Respiratory burst oxidase homologs (Rbohs) are the primary producers of reactive oxygen species (ROS), which have been demonstrated to play critical roles in plant responses to abiotic stress. Here, we explored the function of OsRbohH in heat and drought stress tolerance by generating overexpression lines (OsRbohH-OE). OsRbohH was highly induced by various abiotic stress and hormone treatments. Compared to wild-type (WT) controls, OsRbohH-OE plants exhibited enhanced tolerance to heat and drought, as determined by survival rate analyses and total chlorophyll content. Histochemical staining revealed that OsRbohH-OE accumulated less ROS. This is consistent with the observed increase in catalase (CAT) and peroxidase (POD) activities, as well as a reduced electrolyte leakage rate and malondialdehyde (MDA) content. Moreover, OsRbohH-OE exhibited enhanced sensitivity to exogenous abscisic acid (ABA), accompanied by altered expression levels of ABA synthesis and catabolic genes. Further analysis indicated that transgenic lines had lower transcripts of ABA signaling-related genes (OsDREB2A, OsLEA3, OsbZIP66, and OsbZIP72) under heat but higher levels under drought than WT. In conclusion, these results suggest that OsRbohH is a positive regulator of heat and drought tolerance in rice, which is probably performed through OsRbohH-mediated ROS homeostasis and ABA signaling. [ABSTRACT FROM AUTHOR]

Background: Among several reasons for low productivity in mungbean, various biotic and abiotic factors play a major role. Although intensive research work has been done on genetic architecture of yield and yield attributes of mungbean but limited work was done on yield attributes along with water use efficiency (WUE) and heat stress tolerance related traits. The present study is aimed to identify the genetic potential of mungbean genotypes with high yield and drought and heat stress tolerance. Methods: The F2 seed was harvested from selfed F1 population during 2017-18 from three superior crosses viz., ML 267xLGG 528, MGG 390xLM 95 and LM 95xEC 362096. These crosses were selected based on their per se performance of yield, yield attributes and WUE related traits. Genetic analysis was carried out in F2 populations of three crosses for fourteen quantitative characters to identify the number of transgressive segregants in desirable direction. Result: A good number of transgressive segregants in desirable direction were observed for plant height, number of pods per cluster, harvest index, SLA, SLW and relative injury in the cross ML 267xLGG 528: for plant height, number of branches per plant, SCMR, SLA, SLW and relative injury in the cross MGG 390xLM 95 and for plant height, number of pods per cluster, number of pods per plant SCMR, SLA, SLW, relative injury and seed yield in the cross LM 95xEC 362096. [ABSTRACT FROM AUTHOR]

Simple Summary: This study provides a historical perspective of climate change in relation to chickens and a review of genetic advancements related to heat tolerance in chickens. It highlights the origin of the chickens and how the process of domestication and selective breeding has resulted in genetic variations and increased vulnerability to heat stress. This review also discusses the protective genes and molecular mechanisms, such as heat shock proteins, antioxidants, and immunological response that contribute to heat stress tolerance. Likewise, it discusses the use of further genomic techniques such as the genome-wide association study (GWAS) and quantitative trait locus (QTL) analysis in the identification of genetic variables that contribute to the breeding of broiler chickens with enhanced heat tolerance. Similarly, it highlights the need for including local chickens in breeding programs to enhance genetic diversity. This would help them to better withstand heat stress, addressing the challenge of sustainable poultry production in the context of global warming. Climate change poses a significant threat to the poultry industry, especially in hot climates that adversely affect chicken growth, development, and productivity through heat stress. This literature review evaluates the evolutionary background of chickens with the specific genetic characteristics that can help chickens to cope with hot conditions. Both natural selection and human interventions have influenced the genetic characteristics of the breeds used in the current poultry production system. The domestication of chickens from the Red junglefowl (Gallus gallus) has resulted in the development of various breeds with distinct genetic differences. Over the past few years, deliberate breeding for desirable traits (such as meat production and egg quality) in chickens has resulted in the emergence of various economically valuable breeds. However, this selective breeding has also caused a decrease in the genetic diversity of chickens, making them more susceptible to environmental stressors like heat stress. Consequently, the chicken breeds currently in use may possess a limited ability to adapt to challenging conditions, such as extreme heat. This review focuses on evaluating potential genes and pathways responsible for heat tolerance, including heat shock response, antioxidant defense systems, immune function, and cellular homeostasis. This article will also discuss the physiological and behavioral responses of chicken varieties that exhibit genetic resistance to heat, such as the naked neck and dwarf traits in different indigenous chickens. This article intends to review the current genomic findings related to heat tolerance in chickens that used methods such as the genome-wide association study (GWAS) and quantitative trait loci (QTL) mapping, offering valuable insights for the sustainability of poultry in the face of global warming. [ABSTRACT FROM AUTHOR]

SUMMARY: Plants continuously endure unpredictable environmental fluctuations that upset their physiology, with stressful conditions negatively impacting yield and survival. As a contemporary threat of rapid progression, global warming has become one of the most menacing ecological challenges. Thus, understanding how plants integrate and respond to elevated temperatures is crucial for ensuring future crop productivity and furthering our knowledge of historical environmental acclimation and adaptation. While the canonical heat‐shock response and thermomorphogenesis have been extensively studied, evidence increasingly highlights the critical role of regulatory epigenetic mechanisms. Among these, the involvement under heat of heterochromatic suppression mediated by transcriptional gene silencing (TGS) remains the least understood. TGS refers to a multilayered metabolic machinery largely responsible for the epigenetic silencing of invasive parasitic nucleic acids and the maintenance of parental imprints. Its molecular effectors include DNA methylation, histone variants and their post‐translational modifications, and chromatin packing and remodeling. This work focuses on both established and emerging insights into the contribution of TGS to the physiology of plants under stressful high temperatures. We summarized potential roles of constitutive and facultative heterochromatin as well as the most impactful regulatory genes, highlighting events where the loss of epigenetic suppression has not yet been associated with corresponding changes in epigenetic marks. Significance Statement: High temperatures pose a major threat to plant physiology. While research has extensively focused on thermomorphogenesis and heat‐shock stress responses, the roles of epigenetic mechanisms remain relatively under‐explored. In particular, the contribution of transcriptional gene silencing (TGS) is probably the least studied. Our review highlights how canonical TGS and heterochromatin dynamics may contribute to plant heat tolerance, summarizing both established and novel insights. With this work, we aim to promote alternative avenues for eventually developing heat‐resistant crops, ultimately contributing to more sustainable agriculture under a global warming scenario. [ABSTRACT FROM AUTHOR]

The subject of the current study was to assess the stress indices with the aim to identify the salt tolerant genotypes, in addition to recognize the selection criterion for salinity tolerance. A set of fourteen barley genotypes were screened under two environments as non-stress (Normal) and stress (Salinity) conditions. The experimental material was evaluated in Randomized Block Design during 2021-22 at Research Area of Department of Genetics and Plant Breeding, CCS Haryana Agricultural University, Hisar. The genotypes namely RD 2794, BH 19-49, BH 946 and BH 19-52 were identified salt tolerant based on average rank of SSI of different traits. Further, results based on overall rank of stress indices employed on grain yield, BH 19-13, BH 20-40, BH 393, BH 19-15, BH 20-02 and BH 946 were found most promising exhibiting tolerant to salinity. Correlation analysis discerned significant negative association of grain yield (Ys) with SSI, TOL, SSPI, RSI and RED and significant positive correlation with the indices viz., STI, YI, YSI, MP, GMP, HM and MRP. These indices, therefore, could be considered as the best selection criteria for salinity breeding. PCA indicated first principal component (PC 1) as salt tolerant component based on strong correlation with grain yield (Ys) and STI, YI, YSI, MP, GMP, HM, MRP indices under stress condition. The genotypes of cluster I portrayed better performance under salinity for grain yield (Ys) and SSI, TOL, SSPI, RSI, RED, YI, YSI, and MRP. The genotypes from this cluster could be utilized for salinity tolerance as elite breeding material. [ABSTRACT FROM AUTHOR]

Birds maintain some of the highest body temperatures among endothermic animals. Often deemed a selective advantage for heat tolerance, high body temperatures also limits birds' thermal safety margin before reaching lethal levels. Recent modelling suggests that sustained effort in Arctic birds might be restricted at mild air temperatures, which may require reductions in activity to avoid overheating, with expected negative impacts on reproductive performance. We measured within-individual changes in body temperature in calm birds and then in response to an experimental increase in activity in an outdoor captive population of Arctic, cold-specialised snow buntings (Plectrophenax nivalis), exposed to naturally varying air temperatures (− 15 to 36 °C). Calm buntings exhibited a modal body temperature range from 39.9 to 42.6 °C. However, we detected a significant increase in body temperature within minutes of shifting calm birds to active flight, with strong evidence for a positive effect of air temperature on body temperature (slope = 0.04 °C/ °C). Importantly, by an ambient temperature of 9 °C, flying buntings were already generating body temperatures ≥ 45 °C, approaching the upper thermal limits of organismal performance (45–47 °C). With known limited evaporative heat dissipation capacities in these birds, our results support the recent prediction that free-living buntings operating at maximal sustainable rates will increasingly need to rely on behavioural thermoregulatory strategies to regulate body temperature, to the detriment of nestling growth and survival. [ABSTRACT FROM AUTHOR]

Heat shock, a transient exposure to high temperatures, is a substantial hazard to rice (Oryza sativa L.) production and sustainability. The objective of this review paper is to summarize the impact of heat shock on rice and explore approaches to mitigate its adverse effects to achieve sustainable production. Rice is a staple food for billions of people globally and is extremely sensitive to heat shock. Higher temperatures disturb various physiological and biochemical processes, resulting in decreased growth, development, and ultimately lower grain yield. Heat shock negatively affects important agronomic traits, such as panicle differentiation, pollen viability, fertilization, grain filling, and, ultimately, grain quality. To manage heat shock and sustain rice production, several strategies have been explored, such as modifications to sowing schedules, the substitution of heat-tolerant cultivars for sensitive genotypes, and the use of growth regulators. To improve rice under heat shock, various approaches could be taken: (1) cultivating cultivars that flower early in the morning by adjusting sowing/planting times, modified irrigation, and fertilization; (2) inducing acclimation via growth regulators and organic stimulants and chemicals; (3) breeding genetically resistant cultivars through the integration of appropriate genes; and (4) genetic modification techniques for heat-shock tolerance. Overall, effectively managing heat-shock stress in rice requires a comprehensive strategy that includes developing and using heat shock-tolerant cultivars, adopting suitable cultural practices, utilizing external substances, and applying biotechnological tools. Implementing these strategies collectively will help achieve sustainable rice production in the face of increasing heat-shock conditions.

ABSTRACT: A total of 440 one-day-old healthy male Arbor Acres broilers were equally assigned to a control group (CTL) and an early-age high-temperature exposure (EHT) group (4 replicates per group, 55 chickens per replicate). At d 3, the broilers in CTL group were reared in the normal temperature 33 ± 1°C, while the broilers in EHT group were exposed to 36 ± 1°C for 24 h. At d 43, all broilers were treated with an acute high temperature 35 ± 1°C for 5 h. The results showed that average daily gain in EHT group was decreased at d 3, but average daily gain in EHT group was increased at d 36 to 42 (P < 0.05). Plasma GLU level in EHT group was lower in broilers at d 7 or facing subsequently high temperature for 5 h (P < 0.05). The relative expression of myogenic differentiation (MyoD) gene in pectoralis major and myogenic factor 5 (Myf5) gene in biceps femoris were significantly improved at d 42 after early-age heat exposure (P < 0.05). Broilers in EHT group have a higher temperature tolerance with a lower mortality than control broilers (P < 0.05). Broilers in EHT group have a lower rectal temperature and a higher comb and ear temperature when facing subsequently acute high temperature than control broilers (P < 0.05). In addition, our study demonstrated that early-age heat exposure significantly decreased the mortality and increased the heat tolerance of broilers when facing an acute short-term heat exposures. Early-age heat exposure increased the process of myogenesis via up-regulating the MyoD and Myf5 gene expression in skeletal muscle, which accelerated average daily gain.

Abtract: Climate change; the most concerning issue throughout the globe, is now considered a major cause of heat stress which is deteriorating agricultural crops. A pot experiment was performed to examine the ameliorative role of melatonin foliar spray on growth attributes, physiological attributes and yield and quality attributes of heat-tolerant and heat-sensitive genotypes of tomatoes under heat stress mediated by field environment. The results demonstrated that all the growth parameters of all tomato genotypes such as plant fresh biomass, plant dry biomass, stem girth, leaf area, the number of viable seeds, protein contents as well as physiological attributes including photosynthetic rate, stomatal contents, transpiration rate, chlorophyll contents, water use efficiency (WUE) and synthesis of osmoprotectants including proline and glycine betain (GB) were increased significantly upon foliar application of melatonin @ 25 µM under heat stress except electrolyte leakage (EL), leaf temperature and hydrogen peroxide contents (H2O2) which were decreased in all cultivars of tomato either in heat tolerant or in heat sensitive; as compared to their respective control which remained untreated. Similarly, acivity of enzymatic and non-enzymatic antioxidants including nitric oxide synthase (NOS), glutathione reductase (GR), nitrate reductase (NR) and glutathione S transferase (GST) were also improved upon melatonin foliar application under heat stress. However, the maximum improvement in all measured attributes was observed in all types of tomato genotypes grown under both control and 25 µM melatonine foliar spray treatment. All these findings proved that melatonin spray is capable to address the deteriorative impact of high temperature on tomato growth.

ABSTRACT: Grandparent roosters are crucial in poultry breeding programs and significantly influence future bird generations' genetic makeup and performance. However, these roosters face considerable challenges from heat stress, which can adversely affect their reproductive performance, semen quality, and overall health and welfare. Our study aimed to investigate the effects of heat stress on the genetics of semen characteristics, identify the appropriate temperature and humidity indices (THI), and determine the threshold point of heat stress to prevent thermal stress. We analyzed data from 3,895 records of 242 Thai native grandparent roosters in conjunction with the THI using 7 THI functions and the regression method. The threshold point of heat stress, genetic parameters, rate of decline of semen characteristics per level of THI, estimated breeding values and selection index values were analyzed using the multivariate test-day model in the AIREML and BLUPF90 programs. Based on the regression coefficient and statistical criteria of the lowest −2logL and AIC values, the results showed that a THI of 78 was considered the threshold point of heat stress. The estimated heritability values ranged from 0.023 to 0.032, 0.066 to 0.069, 0.047 to 0.057, and 0.022 to 0.024 for mass movement, semen volume, sperm concentration, and the semen index, respectively. The reduction rates of mass movement, semen volume, sperm concentration, and semen index at a THI of 78 were −0.009, −0.003, −0.170, and −0.083 per THI, respectively. The genetic correlations among the semen traits were moderately to strongly positive and ranged from 0.562 to 0.797. The genetic correlations between semen traits and heat stress were negative and ranged from −0.437 to −0.749. The permanent environmental correlations among the semen traits (0.648–0.929) were positive and greater than the genetic correlations. Permanent environmental correlations between semen traits and heat stress were negative and ranged from −0.539 to −0.773. The results of the selection indices showed that the higher the selection intensity was, the greater the degree to which the selection index corresponded to genetic progress. The recommendation for animal genetic selection is that the top 10% is appropriate because it seems most preferred. Therefore, using a multivariate test-day model and selection index for the high genetic potential of semen traits and heat tolerance in Thai native grandparent roosters makes it possible to achieve genetic assessment in a large population.

Strawberry production is facing a serious decline with the increase in global temperature as a result of climate change. Improving the heat tolerance is imperative for the strawberry plants to remain productive under high temperature conditions. The present work aimed to study the effect of heat acclimation on the thermotolerance of strawberry plants subjected to severe heat stress. Tissue cultured Fragaria ‘Taoyuan No. 1’ plantlets were subjected to four heat-acclimation treatments with gradual increase of temperatures from 30°C to 42°C for 1.25 hr to 10 hr before exposing them to the lethal temperature of 48°C for 4 hr. Survival, new leaf emergence and root growth, electrolyte leakage, chlorophyll and proline contents, as well as antioxidant enzyme activities were compared between the control, acclimated and non-acclimated plantlets. Results indicated that heat acclimation was required for the strawberry plantlets to survive under lethal temperature conditions. The acclimated plantlets registered a lower degree of electrolyte leakage and chlorophyll degradation, and a higher proline content compared to the non-acclimated plantlets. The activities of the antioxidant enzymes increased with the elevation of acclimation temperature and peaked at 42°C except for ascorbate peroxidase (APX) whose activity peaked at 39°C. Higher activities of superoxide dismutase (SOD), APX, glutathione reductase (GR), catalase (CAT) and peroxidase (POD) were observed in the acclimated plantlets compared to the non-acclimated plantlets. This study demonstrates that heat acclimation improved the thermotolerance of in vitro strawberry plantlets by reducing electrolyte leakage and chlorophyll degradation, as well as by enhancing proline content and antioxidant enzyme activities under severe heat stress.

Abstract Chocolate spot and heat stress devastatingly impact the production of faba bean, particularly under prevailing climatic changes and rising drastic environmental conditions. Hence, the adaptability of faba bean performance is a decisive objective of plant breeders to ensure its sustainable production. The present study aimed to evaluate the agronomic performance and stability of diverse eleven faba bean genotypes for yield characters, chocolate spot, and heat stress in eight different growing environments. The faba bean genotypes were evaluated at two sowing dates in two different locations during two growing seasons. The evaluated eleven faba bean genotypes were sown timely in autumn (25 October) and late sowing in early winter (25 November) in Bilbeis and Elkhatara during 2020 and 2021 growing seasons. The results exhibited substantial differences among the evaluated sowing dates, locations, and faba bean genotypes for all studied characters. The genotypes Sakha-3, Nubaria-3, Nubaria-5, Misr-3, and Wadi-1 were able to produce acceptable yield and quality characters under timely sowing in autumn and late sowing in early winter in all tested environments. Moreover, the genotypes Nubaria-3, Nubaria-4, Nubaria-5, Sakha-4, Giza-3, and Triple White exhibited better resistance to chocolate spot. The assessed faba bean genotypes were evaluated under late sowing to expose the plants to high temperature stress at flowering and throughout the anthesis and seed-filling stages. The genotypes Nubaria-5, Nubaria-3, Nubaria-4, Sakha-3, Sakha-4, Wadi-1, and Misr-3 possessed tolerance to heat stress more than the other genotypes. Different statistical methods were applied to study the stability of assessed genotypes such as joint regression, Additive Main Effect and Multiplicative Interaction (AMMI) analysis, AMMI stability value, Wricke's and Ecovalence values. The estimated stability parameters were consistent in depicting the stability of the assessed faba bean genotypes. The findings revealed that Sakha-1, Misr-3, Nubaria-4, and Nubaria-5 demonstrated stable and desirable performance across all tested environments. The heatmap was employed to classify the assessed faba bean genotypes into different groups based on agronomic performance, chocolate spot resistance and heat stress tolerance. Nubaria-3, Nubaria-4, Nubaria-5, and Misr-3 had the best performance for agronomic performance, chocolate spot resistance, and heat stress tolerance. The obtained results provide evidence of employing promising faba bean genotypes for improving the stability of agronomic performance, chocolate spot resistance, and heat stress tolerance in breeding programs principally under unprecedented climate fluctuations.

Classical theories predict that relatively constant environments should generally favour specialists, while fluctuating environments should be selected for generalists. However, theoretical and empirical results have pointed out that generalist organisms might, on the contrary, perform poorly under fluctuations. In particular, if generalism is underlaid by phenotypic plasticity, performance of generalists should be modulated by the temporal characteristics of environmental fluctuations. Here, we used experiments in microcosms of Tetrahymena thermophila ciliates and a mathematical model to test whether the period or autocorrelation of thermal fluctuations mediate links between the level of generalism and the performance of organisms under fluctuations. In the experiment, thermal fluctuations consistently impeded performance compared with constant conditions. However, the intensity of this effect depended on the level of generalism: while the more specialist strains performed better under fast or negatively autocorrelated fluctuations, plastic generalists performed better under slow or positively autocorrelated fluctuations. Our model suggests that these effects of fluctuations on organisms' performance may result from a time delay in the expression of plasticity, restricting its benefits to slow enough fluctuations. This study points out the need to further investigate the temporal dynamics of phenotypic plasticity to better predict its fitness consequences under environmental fluctuations. [ABSTRACT FROM AUTHOR]

There is growing concern about the fate of tropical forests in the face of rising global temperatures. Doughty et al. (2023) suggest that an increase in air temperature beyond ∼4 °C will result in massive death of tropical forest leaves and potentially tree death. However, this prediction relies on assumptions that likely underestimate the heat tolerance of tropical leaves. [ABSTRACT FROM AUTHOR]

Rice is a staple crop in South Korea and globally. The era of global boiling, characterized by rising temperatures and abnormal climatic conditions, significantly impacts crop production worldwide. This study examines the effects of high temperatures and rainfall on early maturing rice varieties, focusing on enhancing heat tolerance during the ripening stage and preharvest sprouting resistance. Utilizing ‘Milyang247,’ a progeny line from ‘Nampyeong,’ we developed the intermediate line ‘MY362VP.’ During 2020–2022, regional adaptability tests were conducted at five locations across Korea. Results showed that ‘MY362VP’ had a viviparous germination rate of 1.9% compared to 19.0% in the control variety ‘Jopyeong.’ Furthermore, ‘MY362VP’ maintained a head rice rate of 90.6% under high temperature conditions, outperforming ‘Jopyeong,’ which has a rate of 62.1%. ‘MY362VP’ produced an average yield of 529 kg/10a, comparable to the control’s 518 kg/10a. This study offers valuable insights for breeding climate-resilient early-maturing rice varieties, positioning ‘MY362VP’ as a promising candidate for future cultivation. [ABSTRACT FROM AUTHOR]

Seasonal acclimatization is known to result in adaptations that can improve heat tolerance. Staff who operate on burn injuries are exposed to thermally stressful conditions and seasonal acclimatization may improve their thermoeffector responses during surgery. Therefore, the aim of this study was to assess the physiological and perceptual responses of staff who operate on burn injuries during summer and winter, to determine whether they become acclimatized to the heated operating theater. Eight staff members had physiological and perceptual responses compared during burn surgeries conducted in thermoneutral (CON: 24.1 ± 1.2°C, 45 ± 7% relative humidity [RH]) and heated (HOT: 31.3 ± 1.6°C, 44 ± 7% RH) operating theaters, in summer and winter. Physiological parameters that were assessed included core temperature, heart rate, total sweat loss, sweat rate, and urinary specific gravity. Perceptual responses included ratings of thermal sensation and comfort. In summer, CON compared to winter CON, baseline (85 ± 15 bpm VS 94 ± 18 bpm), mean (84 ± 16 bpm VS 93 ± 18 bpm), and peak HR (94 ± 17 bpm VS 105 ± 19 bpm) were lower (p < 0.05), whereas core temperature was not different between seasons in either condition (p > 0.05). In HOT, ratings of discomfort were higher in summer (15 ± 3) than winter (13 ± 3; p > 0.05), but ratings of thermal sensation and sweat rate were similar between seasons (p > 0.05). The surgical team in burns in Western Australia can obtain some of the physiological adaptations that result from seasonal acclimatization, but not all. That is most likely due to a lower than required amount of outdoor heat exposure in summer, to induce all physiological and perceptual adaptations. [ABSTRACT FROM AUTHOR]

Temperature influences nearly all aspects of fitness. However, reproduction is often more thermally sensitive than survival. Thermoregulation must maintain performance in both components of fitness to buffer populations from environmental change.We assessed the fitness benefits of thermoregulation in Enchenopa binotata treehoppers. Under realistic mesocosm conditions, we quantified fine‐scale microclimates using 3D‐printed operative temperature models. We then compared operative temperatures to treehopper body temperatures and translated patterns of thermoregulation into variation in survival and reproduction. We also assessed two thermoregulatory mechanisms: precise microclimate choice and heat‐escape behaviours. Finally, we applied our results to evaluate if arthropod thermoregulation is accurately characterized by two theoretical models commonly used to simulate responses to environmental change.We found substantial thermal variation at fine spatial scales relevant to insects: at a single point in time, temperatures within 30‐cm‐tall plants spanned ranges up to 19°C (23–42°C).Lethal operative temperatures were common when air temperatures were high. However, heat escapes allowed treehoppers to almost entirely avoid lethal temperatures.By contrast, individuals thermoconformed in the absence of lethal operative temperatures. This finding suggests that precise microclimate choice imposes high costs due to thermal uncertainty at fine spatial scales. Furthermore, given the narrow range of temperatures in which reproduction occurs, thermoregulation is unlikely to maintain reproduction.Thermoregulation was most effective in the lowest‐quality and most spatially variable thermal habitats. Treehopper thermoregulation therefore more closely follows cost–benefit models of thermoregulation compared to models that account for inhibited movement at extreme temperatures.Overall, even if thermoregulation can prevent lethal heat stress, it may have limited capacity to buffer arthropods and other small ectotherms from environmental change if it cannot maintain reproductive performance. Read the free Plain Language Summary for this article on the Journal blog. [ABSTRACT FROM AUTHOR]

Aphids (Hemiptera: Aphididae) are small, phloem-feeding insects that exhibit remarkable adaptability and resilience to various environmental conditions, including heat stress. Recent research has shed light on the role of bacterial symbionts in influencing the heat tolerance of aphids. Additionally, an intriguing avenue of investigation has explored how aphids can acquire bacterial symbionts through a unique mechanism involving soil nematodes. In this paper, we provide an in-depth overview of the interplay between heat stress, bacterial symbionts, and soil nematodes in the context of aphid biology. In reviewing the existing literature and collating available knowledge, we highlight the mechanisms by which bacterial symbionts contribute to aphid heat stress tolerance and examine the symbiont acquisition process facilitated by soil nematodes. Furthermore, we discuss the implications of these symbiotic associations in relation to the ecology, evolution, and agricultural management of a major globally expanding pest aphid, the corn leaf aphid, Rhopalosiphum maidis (Fitch). Overall, it may be concluded that both primary and secondary bacterial endosymbionts play a significant role in aphid biology with evolutionary consequences. These include adaptations through bacterial symbionts in terms of longevity and fecundity, heat shock tolerance, and resistance to fungal pathogens and primary hymenopterous wasp parasitoids. [ABSTRACT FROM AUTHOR]

Comparative measurements of four Vitis vinifera cultivars were undertaken to assess assimilation tolerance to the high growth temperatures currently pervading Australian and other wine growing regions. The cultivars, cvs. Chardonnay, Merlot, Semillon, and Shiraz, were all grown in common growth conditions, and an hypothesis promulgated genotypic variation in assimilation and in the leaf temperature dependency. Assimilation responses to varying light intensity and to varying chloroplast CO2 at a range of leaf temperatures (15–45°C) were measured in leaves of each cultivar in mid‐summer. Light response curves revealed marked genotype differences in maximum assimilation, but temperature effects also varied. Semillon leaves were most sensitive to temperature, with marked and steep differences in assimilation at different temperatures while Chardonnay and Merlot were least sensitive, with relatively flat responses. There were also marked cultivar differences in response to CO2 and significant effects of leaf temperature. CO2‐saturated assimilation varied markedly, with Semillon and Merlot leaves most responsive to temperature, although there were differences in optimum temperatures and maximum rates. Chardonnay leaves remained least tolerant, with lowest rates of assimilation across most temperatures. Assimilation at 45°C also separated the cultivars and two cultivars had higher rates than at 15°C while Chardonnay and Merlot leaves had higher rates at 15°C. There were no cultivar differences in the temperature dependency of Ribulose 1,5‐bisphosphate (RuBP) carboxylation, but Semillon had a much steeper temperature dependency on RuBP regeneration than the other cultivars. All these responses confirmed the hypothesis and concluded the high‐temperature tolerance of Semillon and Shiraz and the poor adaptability of Chardonnay and possibly Merlot to perform in the current high‐temperature growth conditions. [ABSTRACT FROM AUTHOR]

In alpine ecosystems, elevation broadly functions as a steep thermal gradient, with plant communities exposed to regular fluctuations in hot and cold temperatures. These conditions lead to selective filtering, potentially contributing to species-level variation in thermal tolerance and population-level genetic divergence. Few studies have explored the breadth of alpine plant thermal tolerances across a thermal gradient or the underlying genetic variation thereof. We measured photosystem heat (Tcrit-hot) and cold (Tcrit-cold) thresholds of ten Australian alpine species across elevation gradients and characterised their neutral genetic variation. To reveal the biogeographical drivers of present-day genetic signatures, we also reconstructed temporal changes in habitat suitability across potential distributional ranges. We found intraspecific variation in thermal thresholds, but this was not associated with elevation, nor underpinned by genetic differentiation on a local scale. Instead, regional population differentiation and considerable homozygosity within populations may, in part, be driven by distributional contractions, long-term persistence, and migrations following habitat suitability. Our habitat suitability models suggest that cool-climate-distributed alpine plants may be threatened by a warming climate. Yet, the observed wide thermal tolerances did not reflect this vulnerability. Conservation efforts should seek to understand variations in species-level thermal tolerance across alpine microclimates. [ABSTRACT FROM AUTHOR]

Chocolate spot and heat stress devastatingly impact the production of faba bean, particularly under prevailing climatic changes and rising drastic environmental conditions. Hence, the adaptability of faba bean performance is a decisive objective of plant breeders to ensure its sustainable production. The present study aimed to evaluate the agronomic performance and stability of diverse eleven faba bean genotypes for yield characters, chocolate spot, and heat stress in eight different growing environments. The faba bean genotypes were evaluated at two sowing dates in two different locations during two growing seasons. The evaluated eleven faba bean genotypes were sown timely in autumn (25 October) and late sowing in early winter (25 November) in Bilbeis and Elkhatara during 2020 and 2021 growing seasons. The results exhibited substantial differences among the evaluated sowing dates, locations, and faba bean genotypes for all studied characters. The genotypes Sakha-3, Nubaria-3, Nubaria-5, Misr-3, and Wadi-1 were able to produce acceptable yield and quality characters under timely sowing in autumn and late sowing in early winter in all tested environments. Moreover, the genotypes Nubaria-3, Nubaria-4, Nubaria-5, Sakha-4, Giza-3, and Triple White exhibited better resistance to chocolate spot. The assessed faba bean genotypes were evaluated under late sowing to expose the plants to high temperature stress at flowering and throughout the anthesis and seed-filling stages. The genotypes Nubaria-5, Nubaria-3, Nubaria-4, Sakha-3, Sakha-4, Wadi-1, and Misr-3 possessed tolerance to heat stress more than the other genotypes. Different statistical methods were applied to study the stability of assessed genotypes such as joint regression, Additive Main Effect and Multiplicative Interaction (AMMI) analysis, AMMI stability value, Wricke's and Ecovalence values. The estimated stability parameters were consistent in depicting the stability of the assessed faba bean genotypes. The findings revealed that Sakha-1, Misr-3, Nubaria-4, and Nubaria-5 demonstrated stable and desirable performance across all tested environments. The heatmap was employed to classify the assessed faba bean genotypes into different groups based on agronomic performance, chocolate spot resistance and heat stress tolerance. Nubaria-3, Nubaria-4, Nubaria-5, and Misr-3 had the best performance for agronomic performance, chocolate spot resistance, and heat stress tolerance. The obtained results provide evidence of employing promising faba bean genotypes for improving the stability of agronomic performance, chocolate spot resistance, and heat stress tolerance in breeding programs principally under unprecedented climate fluctuations. [ABSTRACT FROM AUTHOR]

The germplasm with heat-tolerant traits is one of the crucial targets effective in rice (Oryza sativa L.) breeding for climate change. Hence, the presented research aimed to improve heat-tolerant cultivars through traditional breeding and molecular markers for climate change adaptability. The results showed most of the studied rice genotypes had a wide range of variability for various traits, with this range also reflected among the tested crosses. The best crosses with the highest mean values for all traits were Giza178 x Giza179, Giza178 x IET 1444, Sakha104 x IET 1444, and Giza179 x IET 1444. The general combining ability (GCA) effects revealed cultivars IET 1444, Giza179, Giza178, and Sakha104 with significant positive GCA influences for tillers and panicles plant-1, filled grains panicle-1, and grain yield per plant. The best identified crosses for almost all traits were Giza177 x Giza178, Giza177 x Giza179, Giza177 x Sakha104, Giza178 x IET 1444, and Sakha105 x IET 1444. The principal component analysis (PCA) divided the seven rice genotypes into two groups. The first one included the sensitive rice cultivars, namely, Giza177, Sakha105, and Sakha101, and the second group comprised tolerant genotypes, i.e., Giza178, Giza179, IET144, and Sakha104. Using 18 SSR markers helped assess the genetic diversity in rice genotypes. The studied markers produced 204 alleles, with a mean of 11.33 per locus. A higher number of alleles per locus resulted from primers RM493, RM341, RM3297, and RM3330. The polymorphic information content (PIC), a reflection of allele diversity and frequency, was moderate and ranged between 0.157 for RM504 and 0.872 for RM3330, with an average of 0.756. Based on the SSR cluster analysis, rice genotypes formed two groups; the first group included the sensitive rice genotypes, while the second was the tolerant genotypes. [ABSTRACT FROM AUTHOR]

Lettuce has been commonly associated with the contamination of human pathogens, such as Escherichia coli O157:H7 (hereafter O157:H7), which has resulted in serious foodborne illnesses. Contamination events may happen throughout the farm-to-fork chain, when O157:H7 colonizes edible tissues and closely interacts with the plant. Environmental conditions have a significant impact on many plant–microbe interactions; however, it is currently unknown whether temperature affects O157:H7 colonization of the lettuce phyllosphere. In this study, we investigated the relationship between elevated growth temperatures, O157:H7 persistence, and lettuce head growth using 25 lettuce genotypes. Plants were grown under optimal or elevated temperatures for 3.5 weeks before being inoculated with O157:H7. The bacterial population size in the phyllosphere and lettuce head area was estimated at 0- and 10-days postinoculation (DPI) to assess bacterial persistence and head growth during contamination. We found that growing temperature can have a positive, negative, or no effect on O157:H7 persistence depending on the lettuce genotype. Furthermore, temperature had a greater effect on head area size than the presence of O157:H7. The results suggested that the combination of plant genotype and temperature level is an important factor for O157:H7 colonization of lettuce and the possibility to combine desirable food safety traits with heat tolerance into the lettuce germplasm.

Synthetic microbial communities, which simplify the complexity of natural ecosystems while retaining their key features, are gaining momentum in engineering and biotechnology applications. One potential application is the development of bioinoculants, offering an eco-friendly, sustainable solution to promote plant growth and increase resilience to abiotic stresses amidst climate change. A potential source for stress-tolerant microbes is those associated with desert plants, evolved and shaped by selective pressures to promote host health under harsh environmental conditions. In our research, we aim to design and develop synthetic microbial consortia inspired by the natural microbiota of four desert plants native to the Arabian Peninsula, inferred from our previous work identifying the structure and predicting the function of these microbial communities using high throughput eDNA barcoding. To obtain culturable microbes that are manageable and traceable yet still representative of natural microbial communities, we combined multiple experimental protocols coupled with compatibility and synergy assessments, along with in planta testing. We isolated a total of 75 bacteria and conducted detailed biological evaluations, revealing that an overwhelming majority (84 %) of all isolates produced indole acetic acid (IAA), with 73 % capable of solubilizing phosphate, 60 % producing siderophores, 47 % forming biofilms, and 35 % producing ACC deaminase, all contributing to plant growth and stress tolerance. We constructed four synthetic microbial consortia, named EcoBiomes, consisting of synergistic combinations of multiple species that can co-exist without significant antagonism. Our preliminary data indicate that EcoBiomes enhance the resilience of heterologous host plants under simulated environmental stresses, including drought, heat, and salinity. EcoBiomes offer a unique, sustainable, and eco-friendly solution to mitigate the impact of climate change on sensitive ecosystems, ultimately affecting global food security.

ABSTRACT: Chick's susceptibility to heat stress often leads to growth retardation, immune function impairment, disease, and mortality. This thesis explores the potential ameliorative effect of 0.8% Eucommia ulmoides extract (EUE) into the diet of heat-stressed chicks in a 15-d feeding trial. The investigation reveals that feeding EUE significantly enhances the BW, ADG, AFI, and F/G of chicks experiencing heat stress. Additionally, the EUE groups exhibited higher levels of T-AOC (at 7 and 15d), SOD (at 15 d), GSH-Px (at 15 d), as well as lower MDA concentrations (at 7 and 15d) in chick serum. Pathological changes and H&E staining revealed that EUE effectively improved tissue damage in the duodenum, heart, and stomach induced by heat stress in the chicks. The EUE groups also showed higher levels of IgA (at 7 d), IgG and IgM (at 7 and 15 d). RNA-seq and WGCNA analysis revealed that EUE mitigates cellular damage and losses in heat-stressed chicks primarily through pathways involving signal transduction, protein synthesis and degradation, as well as cell cycle regulation, particularly the latter. This investigation serves as a fundamental and cognitive framework for the development and application of Eucommia ulmoides feed additives aimed at safeguarding the well-being of chicks in adverse environmental conditions.

Potato plants are often subjected to heat stress during growth and development, resulting in loss of yield and quality. However, the possibility exists that commercially important genotypes show tolerance to heat stress. In this study, we aim to investigate the morphological and physiological effects of moderate conditions of heat stress on tuberization in nine potato genotypes, and how it affects propagation using an ex vitro and in vitro system. The plant material came from the In Vitro Germplasm Bank of the International Potato Center (CIP). The incubation temperatures of the cultures in in vitro and ex vitro conditions were the ambient in the laboratory and greenhouse, respectively. In in vitro system a randomized complete block design was employed in nine genotypes, two treatments: multiplication culture medium and the same culture medium supplemented with 8.0% sucrose and 500 mg/L-1 CCC, six flasks and five explants per experimental unit. Among all genotypes evaluated, Leona and Liberteña did not form tubers under ex vitro treatment conditions. Under in vitro conditions, Amarilis, Capiro, Perricholi and Tacna showed no evidence of tuberization, and Canchán was the only genotype where 100% formation of tuberous structures were produced in all evaluations. The findings concluded in this study showed that of all the potatoes evaluated, Canchán best responded to the evaluations under both in ex vitro and in vitro conditions, at maximum temperatures between 22.4 to 26.9 and 27.0 to 28.2 oC, respectively. Therefore, it is vitally important to consider its development potential in different producing locations around the world, which are directly and indirectly affected by climate change.

Abstract Background The reliance on a solitary linear reference genome has imposed a significant constraint on our comprehensive understanding of genetic variation in animals. This constraint is particularly pronounced for non-reference sequences (NRSs), which have not been extensively studied. Results In this study, we constructed a pig pangenome graph using 21 pig assemblies and identified 23,831 NRSs with a total length of 105 Mb. Our findings revealed that NRSs were more prevalent in breeds exhibiting greater genetic divergence from the reference genome. Furthermore, we observed that NRSs were rarely found within coding sequences, while NRS insertions were enriched in immune-related Gene Ontology terms. Notably, our investigation also unveiled a close association between novel genes and the immune capacity of pigs. We observed substantial differences in terms of frequencies of NRSs between Eastern and Western pigs, and the heat-resistant pigs exhibited a substantial number of NRS insertions in an 11.6 Mb interval on chromosome X. Additionally, we discovered a 665 bp insertion in the fourth intron of the TNFRSF19 gene that may be associated with the ability of heat tolerance in Southern Chinese pigs. Conclusions Our findings demonstrate the potential of a graph genome approach to reveal important functional features of NRSs in pig populations.

Lily is an important cut flower worldwide and prefers cool environments. The high summer temperature in China affects the quality and quantity of cut lily–flower production. In this study, the heat stress transcription factor HsfA2 was cloned from two cultivated commercial varieties, Lilium longiflorum 'White Heaven' and Lilium oriental 'Siberia', which have different responses to heat stress. An actin-interacting protein 3 (AIP3) domain was found in LlHsfA2 of Lilium longiflorum 'White Heaven' but did not appear in LoHsfA2 of Lilium oriental 'Siberia' using prediction from the simple modular architecture research tool (SMART) website. The genes LlACTIN and LoACTIN were cloned, and their amino acid sequences were found to be the same, so they were named LACTIN. There was an interaction between LlHsfA2 and LACTIN, whereas this interaction did not occur between LoHsfA2 and LACTIN based upon the bimolecular fluorescence complementary (BiFC) experiments. The silenced plants of LlHsfA2 and LACTIN were sensitive to heat stress treatment using barley stripe mosaic virus (BSMV) induced gene silencing in 'White Heaven', and LoHsfA2 silenced plants were also sensitive in 'Siberia'. In contrast, LACTIN silenced plants in 'Siberia' were normal. The expressions of LlHsfA2 or LACTIN were reduced in the LACTIN or LlHsfA2 silenced 'White heaven' plants, whereas the expressions of LoHsfA2 or LACTIN were normal in the LACTIN or LoHsfA2 silenced 'Siberia' plants. In conclusion, the diversity of protein interactions between HsfA2 and ACTIN may affect the distinctness of the heat stress response in different lily varieties, which provides new knowledge for further study on the heat stress response in lily.

To elucidate how rising temperatures influence native amphipods, and how the expansion of wastewater treatment plants (WWTPs) with a fourth purification stage can alter temperature-related effects, studies were conducted in anthropogenically influenced rivers in Southwest Germany. Gammarids were sampled up- and downstream of two WWTPs, and exposed to elevated temperatures in the laboratory. Gammarids separated from precopula pairs were more sensitive to exposure-related stress and to a temperature increase than animals that were not in the reproductive phase. Furthermore, females were significantly more sensitive than males. Adult gammarids sampled individually at the WWTP with three purification stages showed a similar tolerance to elevated temperature at the up- and downstream site. In contrast, mortality following heat stress was substantially lower in animals sampled downstream of the WWTP with four treatment stages than in those sampled at the upstream site. We assume that the increased sensitivity of artificially separated precopula pairings reflect the situation under high hydraulic stress after heavy rainfall. Our results further illustrate the importance of WWTP upgrades in the context of climate change: gammarids sampled downstream the upgraded fourth-stage WWTP were likely exposed to lower levels of micropollutants, and thus may have allocated energy from detoxification to heat stress responses.