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One significant environmental element influencing the growth and yield of rice (Oryza sativa L.) is high temperature. Nevertheless, the mechanism by which rice responds to high temperature is not fully understood. A rice glycosyltransferase gene, OsDUGT1 , was identified as a heat-responsive gene in this investigation. Its function was studied by overexpression and knockout methods. The results showed that under heat stress, OsDUGT1 overexpression lines (OsDUGT1 -OE) increased the survival rate of rice, while Osdugt1 knockout lines (Osdugt1 -ko) decreased the survival rate compared to wild type (ZH11). In addition to rice, heat stress tolerance was also improved by ectopic expression of OsDUGT1 in transgenic Arabidopsis thaliana plants. We observed that ROS scavenging ability, malondialdehyde accumulation, and the ion leakage are relevant to the expression level of OsDUGT1. Through enzyme activity analysis, we found that OsDUGT1 could glycosylate flavonoid compounds. Correspondingly, the loss of OsDUGT1 function caused a significant decrease in endogenous flavonoid accumulation in rice, which was demonstrated by our metabolomics analysis. Additionally, our transcriptomic analysis of Osdugt1 mutant lines under heat stress condition indicated that mutation of OsDUGT1 can reduce the transcriptional activity of heat response related genes, antioxidant enzyme genes and other genes involved in the flavonoid biosynthetic pathway. In summary, our work revealed that OsDUGT1 plays a crucial role in adjusting and balancing the overall plant metabolism and transcription under heat stress through glycosylation of flavonoids, and offers a key prospect gene for breeding efforts to enhance crop heat tolerance under the trend of climate warming all over the globe. [ABSTRACT FROM AUTHOR]

Heat stress affects the growth and development of Brassicaceae crops. Plant breeders aim to mitigate the effects of heat stress by selecting for heat stress tolerance, but the genes responsible for heat stress in Brassicaceae remain largely unknown. During heat stress, heat shock proteins (HSPs) function as molecular chaperones to aid in protein folding, and heat shock transcription factors (HSFs) serve as transcriptional regulators of HSP expression. We identified 5002 heat shock related genes, including HSPs and HSFs, across 32 genomes in Brassicaceae. Among these, 3347 genes were duplicated, with segmented duplication primarily contributing to their expansion. We identified 466 physical gene clusters, including 240 homogenous clusters and 226 heterogeneous clusters, shedding light on the organization of heat shock related genes. Notably, 37 genes were co-located with published thermotolerance quantitative trait loci, which supports their functional role in conferring heat stress tolerance. This study provides a comprehensive resource for the identification of functional Brassicaceae heat shock related genes, elucidates their clustering and duplication patterns and establishes the genomic foundation for future heat tolerance research. We hypothesise that genetic variants in HSP and HSF genes in certain species have potential for improving heat stress tolerance in Brassicaceae crops. [ABSTRACT FROM AUTHOR]

Heat stress faced by the crop plants at seedling stage hinders its growth and if faced at reproductive stage affects crop production. Globally, maize (Zea mays L.) loses a substantial amount of its production due to very high temperatures at anthesis stage during spring season. So, development of heat tolerant maize cultivars is important for maize breeders. The ability of a plant to tolerate heat stress at seedling and reproductive stage is linked with each other and screening at the seedling stage could accelerate the selection process. In the present study, 50 maize inbred lines were screened for heat tolerance at seedling stage under in vitro conditions. Our results showed that parameters such as root length (RL), shoot length (SL), shoot fresh weight (SFW), shoot dry weight (SDW), root fresh weight (RFW), root dry weight (RDW), leaf area (LA), leaf fresh weight (LFW), leaf dry weight (LDW), relative water content (RWC), membrane stability index (MSI) and total chlorophyll (TCHL) showed a significant decrease under heat stress (p < 0.05). Further, morpho-physiological traits were delineated by principal component analysis (PCA). Hierarchical cluster analysis (HCA) was done with the objective to characterize the maize inbred lines based on their response under heat stress. Among the four column clusters, column cluster I showed highest mean values for maximum traits, i.e., RL (16.45 cm), RFW (0.27 g), SL (28.42 cm), SFW (0.74 g), SDW (63.03 mg), LFW (0.16 g), LDW (20 mg) and RWC (48.63%), suggesting that these traits were superior over other traits and inbred lines falling in this cluster would be selected directly on the basis of these traits. The heat tolerance index (HTI) of all the inbred lines based on individual traits was calculated and inbred lines were ranked accordingly. The top five inbred lines: LM22, CML579, LM13, LM16 and RIL 33 performed best under heat stress as they had high heat tolerance index value. The results obtained by PCA and HCA were in accordance with those obtained on the basis of HTI. Our study identified heat tolerant inbred lines of different heterotic pools which, after field validation, can be used for development of heat tolerant maize hybrids. [ABSTRACT FROM AUTHOR]

Background: Among the constraints for low yield of mungbean, drought stress and heat stress are prominent. Water deficits and high temperature occur together in many environments and both stresses can interact to reduce yields. Thus, combination of water use efficiency and high temperature tolerance traits are relevant rather than a single trait used as selection criteria for screening appropriate plant ideotype. The present study is contemplated to identify superior parents for yield, yield attributes, water use efficiency and thermo tolerance related traits through combining ability analysis. Methods: Twenty one F1 crosses were generated by crossing seven diverse mungbean genotypes viz., ML 267, LGG 528, MGG 390, WGG 42, AKM 9904, LM 95 and EC 362096 in a 7 x 7 diallel fashion without reciprocals. Further, 21 F1 crosses along with seven parents were evaluated to study the the mean performance of the seven parents and their 21 F1 crosses and combining ability of the parents and crosses and gene action for yield, yield components and water use efficiency related traits. Result: The present investigations confirmed that some of the parents with significant positive gca effects for seed yield per plant and showed significant positive gca effects for one or more yield, WUE and heat stress tolerance contributing traits. Combination of mean performance and gca effects would result in the selection of potential parents with good reservoir of superior genes. The parents which exhibited high per se performance also displayed good general combining ability effects. Hence, per se performance may be used effectively for the selection of parents. In the present study, MGG 390, ML 267 and EC 362096 were adjudged as the best parents based on both mean and gca effects. [ABSTRACT FROM AUTHOR]

Heat as an abiotic stress significantly impairs the sustainable productivity of wheat (Triticum aestivum L.). To determine the tolerance of genotypes to heat stress, a comprehensive approach should be used that integrates simultaneous phenotyping and genotyping analyses. The aim of this study is to identify local heat-tolerant genotypes using simple sequence repeat (SSR) markers and evaluate the selected genotypes under field conditions for their tolerance to heat stress. Of the 12 SSR markers that showed polymorphism, eight were associated with six important traits. The use of hierarchical cluster analysis (HC) based on SSR markers led to the identification of 13 genotypes that showed varying results and were grouped into three distinct heat tolerance classes: tolerant (T), moderately tolerant (MT), and sensitive (S). The results showed that heat stress had a significant effect on 19 traits under this study, with significant variation in tolerance to heat stress between genotypes. The tolerant genotypes exhibited a range of average thousand-kernel weight (TKW) values between 40.56 and 44.85, while the sensitive genotype (Yecora Rojo) had an average TKW of 35.45. Furthermore, the tolerant genotypes showed two to three times higher levels of antioxidants compared to the sensitive genotypes when exposed to heat stress. Among the traits analyzed, six showed a favorable combination of high heritability (>60%) and genetic gain (>20%). Through the integration of principal component analysis and stepwise multiple linear regression, it was determined that six traits (grain yield, 1000-kernel weight, plant height, intercellular carbon dioxide, flag leaf area, and grain filling duration) revealed differences between the 13 genotypes. HC analysis of the six traits resulted in the same division of genotypes into three main categories as observed in an HC analysis based on SSR markers. It is worth noting that Saudi wheat, including KSU106, KSU105, and KSU115 as local genotypes, in addition to the 16HTWYT-22 genotype, showed higher heat tolerance compared to the other genotypes tested, indicating its potential suitability for agriculture in Saudi Arabia. These results contribute to breeding programs focused on developing heat-tolerant wheat varieties and accelerate progress in wheat productivity improvement programs. [ABSTRACT FROM AUTHOR]

One significant environmental element influencing the growth and yield of rice (Oryza sativa L.) is high temperature. Nevertheless, the mechanism by which rice responds to high temperature is not fully understood. A rice glycosyltransferase gene, OsDUGT1, was identified as a heat-responsive gene in this investigation. Its function was studied by overexpression and knockout methods. The results showed that under heat stress, OsDUGT1 overexpression lines (OsDUGT1-OE) increased the survival rate of rice, while Osdugt1 knockout lines (Osdugt1-ko) decreased the survival rate compared to wild type (ZH11). In addition to rice, heat stress tolerance was also improved by ectopic expression of OsDUGT1 in transgenic Arabidopsis thaliana plants. We observed that ROS scavenging ability, malondialdehyde accumulation, and the ion leakage are relevant to the expression level of OsDUGT1. Through enzyme activity analysis, we found that OsDUGT1 could glycosylate flavonoid compounds. Correspondingly, the loss of OsDUGT1 function caused a significant decrease in endogenous flavonoid accumulation in rice, which was demonstrated by our metabolomics analysis. Additionally, our transcriptomic analysis of Osdugt1 mutant lines under heat stress condition indicated that mutation of OsDUGT1 can reduce the transcriptional activity of heat response related genes, antioxidant enzyme genes and other genes involved in the flavonoid biosynthetic pathway. In summary, our work revealed that OsDUGT1 plays a crucial role in adjusting and balancing the overall plant metabolism and transcription under heat stress through glycosylation of flavonoids, and offers a key prospect gene for breeding efforts to enhance crop heat tolerance under the trend of climate warming all over the globe.

Abstract Background As the greenhouse effect intensifies, global temperatures are steadily increasing, posing a challenge to bread wheat (Triticum aestivum L.) production. It is imperative to comprehend the mechanism of high temperature tolerance in wheat and implement breeding programs to identify and develop heat-tolerant wheat germplasm and cultivars. Results To identify quantitative trait loci (QTL) related to heat stress tolerance (HST) at seedling stage in wheat, a panel of 253 wheat accessions which were re-sequenced used to conduct genome-wide association studies (GWAS) using the factored spectrally transformed linear mixed models (FaST-LMM). For most accessions, the growth of seedlings was found to be inhibited under heat stress. Analysis of the phenotypic data revealed that under heat stress conditions, the main root length, total root length, and shoot length of seedlings decreased by 47.46%, 49.29%, and 15.19%, respectively, compared to those in normal conditions. However, 17 varieties were identified as heat stress tolerant germplasm. Through GWAS analysis, a total of 115 QTLs were detected under both heat stress and normal conditions. Furthermore, 15 stable QTL-clusters associated with heat response were identified. By combining gene expression, haplotype analysis, and gene annotation information within the physical intervals of the 15 QTL-clusters, two novel candidate genes, TraesCS4B03G0152700/TaWRKY74-B and TraesCS4B03G0501400/TaSnRK3.15-B, were responsive to temperature and identified as potential regulators of HST in wheat at the seedling stage. Conclusions This study conducted a detailed genetic analysis and successfully identified two genes potentially associated with HST in wheat at the seedling stage, laying a foundation to further dissect the regulatory mechanism underlying HST in wheat under high temperature conditions. Our finding could serve as genomic landmarks for wheat breeding aimed at improving adaptation to heat stress in the face of climate change.

Background: As the greenhouse effect intensifies, global temperatures are steadily increasing, posing a challenge to bread wheat (Triticum aestivum L.) production. It is imperative to comprehend the mechanism of high temperature tolerance in wheat and implement breeding programs to identify and develop heat-tolerant wheat germplasm and cultivars. Results: To identify quantitative trait loci (QTL) related to heat stress tolerance (HST) at seedling stage in wheat, a panel of 253 wheat accessions which were re-sequenced used to conduct genome-wide association studies (GWAS) using the factored spectrally transformed linear mixed models (FaST-LMM). For most accessions, the growth of seedlings was found to be inhibited under heat stress. Analysis of the phenotypic data revealed that under heat stress conditions, the main root length, total root length, and shoot length of seedlings decreased by 47.46%, 49.29%, and 15.19%, respectively, compared to those in normal conditions. However, 17 varieties were identified as heat stress tolerant germplasm. Through GWAS analysis, a total of 115 QTLs were detected under both heat stress and normal conditions. Furthermore, 15 stable QTL-clusters associated with heat response were identified. By combining gene expression, haplotype analysis, and gene annotation information within the physical intervals of the 15 QTL-clusters, two novel candidate genes, TraesCS4B03G0152700/TaWRKY74-B and TraesCS4B03G0501400/TaSnRK3.15-B, were responsive to temperature and identified as potential regulators of HST in wheat at the seedling stage. Conclusions: This study conducted a detailed genetic analysis and successfully identified two genes potentially associated with HST in wheat at the seedling stage, laying a foundation to further dissect the regulatory mechanism underlying HST in wheat under high temperature conditions. Our finding could serve as genomic landmarks for wheat breeding aimed at improving adaptation to heat stress in the face of climate change. [ABSTRACT FROM AUTHOR]

A significant threat to the ongoing rise in temperature caused by global warming. Plants have many stress-resistance mechanisms, which is responsible for maintaining plant homeostasis. Abiotic stresses largely increase gaseous molecules' synthesis in plants. The study of gaseous signaling molecules has gained attention in recent years. The role of gaseous molecules, such as nitric oxide (NO), hydrogen sulfide (H2S), carbon dioxide (CO2), carbon monoxide (CO), methane (CH4), and ethylene, in plants under temperature high-temperature stress are discussed in the current review. Recent studies revealed the critical function that gaseous molecules play in controlling plant growth and development and their ability to respond to various abiotic stresses. Here, we provide a thorough overview of current advancements that prevent heat stress-related plant damage via gaseous molecules. We also explored and discussed the interaction of gaseous molecules. In addition, we provided an overview of the role played by gaseous molecules in high-temperature stress responses, along with a discussion of the knowledge gaps and how this may affect the development of high-temperature-resistant plant species. [ABSTRACT FROM AUTHOR]

Plant growth and production can be adversely affected by high temperature stress, which is defined as an increase in temperature over a threshold level. 5-aminolevulinic acid (ALA) can be used as a beneficial growth regulator in agriculture, particularly for plants experiencing abiotic stress. The efficacy of exogenous two form ALA application (bulk and nanoencapsulated) was investigated in a factorial experiment based on a completely randomized block design with 12 replications. In this study, different temperatures (optimal temperature 25 °C, and high temperature 35 °C) and different ALA treatments were used (control, 1 mM of ALA, and 1 mM Nano-encapsulated N-ALA). The study revealed that elevated temperatures of 35 °C had an adverse impact on the majority of bell pepper growth characteristics. Nevertheless, the application of ALA and N-ALA significantly enhanced the growth characteristics under these conditions. In contrast to the conditions at 25 °C, the concentrations of potassium (K), proline, electrolyte leakage (EL), glucose, and fructose exhibited an increase at 35 °C. However, both forms of ALA were effective in mitigating these adverse effects. Comparatively, the control treatment showed elevated levels of peroxidase (POD), superoxide dismutase (SOD), and catalase (CAT) enzymes, along with increased malondialdehyde (MDA) levels compared to the ALA treatment. The treatment with ALA resulted in the highest fresh weight and shoot length at 35 °C compared to N-ALA. Conversely, at the same temperature, N-ALA led to a 17 % increase in chlorophyll fluorescence and a 32 % increase in DPPH compared to ALA. In summary, the application of both ALA and Nano-encapsulated N-ALA effectively mitigates the adverse effects of exposure to 35 °C on bell pepper growth and biochemical parameters.

Rhizobacteria from various ecological niches display variations in physiological characteristics. This study investigates the transcriptome profiling of two Bacillus subtilis strains, BsCP1 and BsPG1, each isolated from distinct environments. Gene expression linked to the synthesis of seven types of antibiotic compounds was detected in both BsCP1 and BsPG1 cultures. Among these, the genes associated with plipastatin synthesis were predominantly expressed in both bacterial strains. However, genes responsible for the synthesis of polyketide, subtilosin, and surfactin showed distinct transcriptional patterns. Additionally, genes involved in producing exopolysaccharides (EPS) showed higher expression levels in BsPG1 than in BsCP1. Consistently with this, a greater quantity of EPS was found in the BsPG1 culture compared to BsCP1. Both bacterial strains exhibited similar effects on Arabidopsis seedlings, promoting root branching and increasing seedling fresh weight. However, BsPG1 was a more potent enhancer of drought, heat, and copper stress tolerance than BsCP1. Treatment with BsPG1 had a greater impact on improving survival rates, increasing starch accumulation, and stabilizing chlorophyll content during the post-stress stage. qPCR analysis was used to measure transcriptional changes in Arabidopsis seedlings in response to BsCP1 and BsPG1 treatment. The results show that both bacterial strains had a similar impact on the expression of genes involved in the salicylic acid (SA) and jasmonic acid (JA) signaling pathways. Likewise, genes associated with stress response, root development, and disease resistance showed comparable responses to both bacterial strains. However, treatment with BsCP1 and BsPG1 induced distinct activation of genes associated with the ABA signaling pathway. The results of this study demonstrate that bacterial strains from different ecological environments have varying abilities to produce beneficial metabolites for plant growth. Apart from the SA and JA signaling pathways, ABA signaling triggered by PGPR bacterial strains could play a crucial role in building an effective resistance to various abiotic stresses in the plants they colonize. [ABSTRACT FROM AUTHOR]

A significant threat to the ongoing rise in temperature caused by global warming. Plants have many stress-resistance mechanisms, which is responsible for maintaining plant homeostasis. Abiotic stresses largely increase gaseous molecules’ synthesis in plants. The study of gaseous signaling molecules has gained attention in recent years. The role of gaseous molecules, such as nitric oxide (NO), hydrogen sulfide (H2S), carbon dioxide (CO2), carbon monoxide (CO), methane (CH4), and ethylene, in plants under temperature high-temperature stress are discussed in the current review. Recent studies revealed the critical function that gaseous molecules play in controlling plant growth and development and their ability to respond to various abiotic stresses. Here, we provide a thorough overview of current advancements that prevent heat stress-related plant damage via gaseous molecules. We also explored and discussed the interaction of gaseous molecules. In addition, we provided an overview of the role played by gaseous molecules in high-temperature stress responses, along with a discussion of the knowledge gaps and how this may affect the development of high-temperature-resistant plant species.

Recently, CRISPR-Cas9-based genome editing has been widely used for plant breeding. In our previous report, a tomato gene encoding hybrid proline-rich protein 1 (HyPRP1), a negative regulator of salt stress responses, has been edited using a CRISPR-Cas9 multiplexing approach that resulted in precise eliminations of its functional domains, proline-rich domain (PRD) and eight cysteine-motif (8CM). We subsequently demonstrated that eliminating the PRD domain of HyPRP1 in tomatoes conferred the highest level of salinity tolerance. In this study, we characterized the edited lines under several abiotic and biotic stresses to examine the possibility of multiple stress tolerance. Our data reveal that the 8CM removal variants of HK and the KO alleles of both HK and 15T01 cultivars exhibited moderate heat stress tolerance. Similarly, plants carrying either the domains of the PRD removal variant (PR1v1) or 8CM removal variants (PR2v2 and PR2v3) showed better germination under osmosis stress (up to 200 mM mannitol) compared to the WT control. Moreover, the PR1v1 line continuously grew after 5 days of water cutoff. When the edited lines were challenged with pathogenic bacteria of Pseudomonas syringae pv. tomato (Pto) DC3000, the growth of the bacterium was significantly reduced by 2.0- to 2.5-fold compared to that in WT plants. However, the edited alleles enhanced susceptibility against Fusarium oxysporum f. sp. lycopersici, which causes fusarium wilt. CRISPRCas9- based precise domain editing of the SlHyPRP1 gene generated multistress-tolerant alleles that could be used as genetic materials for tomato breeding. [ABSTRACT FROM AUTHOR]

• The present study highlights differences in growth, physiology and yield of sweet potato grown under different seasons and growing conditions. • Exposing sweet potato plants to heat stress (+2–6°C) severely affected sweet potato physiology and tuber yield. • Foliar application of 0.2% CaCl 2 facilitated the maintenance of high relative water content and photosynthetic rates under heat stress thereby leading to higher biomass growth and tuber yield. It is most elusive and challenging to sustain the productivity of sweet potato under extreme climatic scenarios. Heat stress is major abiotic stress affecting sweet potato productivity. One of the approaches to manage heat stress is to develop suitable and feasible agronomic strategies. With this objective, current experiment was planned to ameliorate heat stress tolerance in sweet potato with exogenous application of 6-Benzyladenine (0.1%; BA), calcium chloride (0.2%; CaCl 2), salicylic acid (0.2%; SA) to compare the differences against water spray (control). Planting sweet potato under three different seasons (I, II and III) and three different growing conditions (OPEN, HUM+ and HUM-) significantly impacted morpho-physiological, biochemical and yield parameters. The highest mean tuber yield was recorded under season III followed by season II and I. Growing condition 2 (G2) i.e. polychamber structure with humidifier operated throughout the cropping period (HUM+) was the most suitable growing condition with the realization of the highest photosynthetic efficiency and tuber yield in comparison to open field (OPEN) and HUM- condition. Heat stress was induced in HUM- condition (polychamber structure with humidifier stopped during 2–3 months after planting). All the parameters declined significantly (P<0.0001) upon exposing plants to ∼32 to 37.5°C of heat stress (+2–6°C of stress as compared to OPEN and HUM+) under HUM- condition. The mean tuber yield reduced up to 18–44, 35–41 and 5–6%, under season I, II and III in comparison to OPEN and HUM+ conditions, respectively. Application of 0.2% CaCl 2 had an improved effect on above-ground biomass, photosynthetic efficiency, biochemical parameters under heat stress resulting into 22–35 (season I), 20–28 (season II) and 13–22% (season III) of increment in mean tuber yield across different growing conditions in comparison to control. Further, a positive and significant relation was observed between leaf area index (r2=0.402), photosynthesis (r2=0.399), relative water content (r2=0.336) and harvest index (r2=0.398) with tuber yield. Evident from this study, application of CaCl 2 , 6-Benzyladenine and salicylic acid significantly ameliorated the negative effects of heat stress. Integration of this agronomic strategy into the future cropping system may enhance the resilience of sweet potato. Furthermore, there is a requisite to assess the efficacy of these chemicals across various ecosystems to develop location specific heat stress management strategy for sweet potato. [ABSTRACT FROM AUTHOR]

As a common adverse environmental factor, heat stress (HS) not only drastically changes the plant transcriptome at the transcription level but also increases alternative splicing (AS), especially intron retention (IR) events. However, the exact mechanisms are not yet well understood. Here, we reported that NTCrelated protein 1 (NTR1), which acts as an accessory component for spliceosome disassembly, is necessary for this process. The mutants of NTR1, both the T-DNA insertion and the point mutation identified through ethyl methanesulfonate (EMS) mutagenesis screening, are vulnerable to HS, indicating that NTR1 is essential for plant HS tolerance. At the molecular level, genes of response to heat and response to temperature stimulus are highly enriched among those of heat-induced but less-expressed ntr1 mutants. Moreover, a large portion of HS response (HSR) genes such as heat shock transcription factors (HSFs) and heat shock proteins (HSPs) are less induced by heat treatment, and more AS events, especially IR events, were found in heattreated ntr1 mutants. Furthermore, HS suppressed the expression of NTR1 and NTR1-associated complex components. Thus, it is very likely that upon HS, the plant reduces the expression of the NTR1-associated complex to fulfill the fast demands for transcription of HSR genes such as HSFs and HSPs, which in turn results in the accumulation of improperly spliced especially IR products and eventually causes harm to plants. [ABSTRACT FROM AUTHOR]

Heat stress is a genetically complex and physiologically diverse phenomenon. To overcome the effect of heat stress identification of genomic locations associated with heat stress tolerance is essential. This article provides the dataset of phenotyping used in the research article entitled “Mapping QTLs for grain yield components in wheat under heat stress”. The presented data included the phenotyping of the 249 RIL population of F8 and F9 generations under timely and late sown conditions during the 2013-14 and 2014-15 crop seasons, respectively. The RIL population was derived from the cross between HUW510 and HD2808 wheat genotypes. A total of eight agronomic traits were subjected to phenotype and the heat susceptibility index (HSI) of these traits was estimated to identify the effect of heat stress on the parents and RIL population. The presented dataset could be utilized to understand the genetic basis for heat stress tolerance in wheat.

Heat stress substantially reduces the yield potential of wheat (Triticum aestivum L.), one of the most widely cultivated staple crops, and greatly threatens global food security in the context of global warming. However, few studies have explored the heat stress tolerance (HST)-related genetic resources in wheat. Here, we identified and fine-mapped a wheat HST locus, TaHST2 , which is indispensable for HST in both the vegetative and reproductive stages of the wheat life cycle. The studied pair of near isogenic lines (NILs) exhibited diverse morphologies under heat stress, based on which we mapped TaHST2 to a 485 kb interval on chromosome arm 4DS. Under heat stress, TaHST2 confers a superior conversion rate from soluble sugars to starch in wheat grains, resulting in faster grain filling and a higher yield potential. A further exploration of genetic resources indicated that TaHST2 underwent strong artificial selection during wheat domestication, suggesting it is an essential locus for basal HST in wheat. Our findings provide deeper insights into the genetic basis of wheat HST and might be useful for global efforts to breed heat-stress-tolerant cultivars. [ABSTRACT FROM AUTHOR]

Increasing global temperature has adverse effects on crop health and productivity at both seedling and reproductivity stages. It is paramount to develop heat tolerant wheat cultivars able to sustain under high and fluctuating temperature conditions. An experiment was conducted to characterize 194 historical wheat cultivars of Pakistan under high temperature at seedling stage to identify loci associated with heat tolerance using genome-wide association studies (GWAS). A quantitative trait locus, TaHST1, on chr4A was also characterized to identify the haplotypes at this locus associated with heat tolerance in wheat from Pakistan. Initially, the diversity panel was planted under control conditions (25°C/20°C day and night temperature) in a glass house. At three leaf stage, plants were subjected to heat stress (HS) by increasing temperature (40°C/35°C day and night), while one treatment was kept at control condition. After 7days of HS, data were collected for seedling morphology. Heat stress reduced these traits by 25% (root weight) to 40% (shoot weight), and shoot biomass was largely affected by heat stress. A GWAS model, fixed and random model circulating probability unification (FarmCPU), identified 43 quantitative trait nucleotides (QTNs) on all chromosomes, except chr7B, were associated under both HS and control conditions. Thirteen QTNs were identified in control, while 30 QTNs were identified in HS condition. In total, 24 haplotypes were identified at TaHST1 locus, and most of the heat tolerant genotypes were assigned to Hap-20 and Hap-21. Eleven QTNs were identified within 0.3-3.1Mb proximity of heat shock protein (HSP). Conclusively, this study provided a detailed genetic framework of heat tolerance in wheat at the seedling stage and identify potential genetic regions associated with heat tolerance which can be used for marker assisted selection (MAS) in breeding for heat stress tolerance. [ABSTRACT FROM AUTHOR]

Key message: Ethanol priming induces heat stress tolerance by the stimulation of unfolded protein response. Global warming increases the risk of heat stress-related yield losses in agricultural crops. Chemical priming, using safe agents, that can flexibly activate adaptive regulatory responses to adverse conditions, is a complementary approach to genetic improvement for stress adaptation. In the present study, we demonstrated that pretreatment of Arabidopsis with a low concentration of ethanol enhances heat tolerance without suppressing plant growth. We also demonstrated that ethanol pretreatment improved leaf growth in lettuce (Lactuca sativa L.) plants grown in the field conditions under high temperatures. Transcriptome analysis revealed a set of genes that were up-regulated in ethanol-pretreated plants, relative to water-pretreated controls. Binding Protein 3 (BIP3), an endoplasmic reticulum (ER)-stress marker chaperone gene, was among the identified up-regulated genes. The expression levels of BIP3 were confirmed by RT-qPCR. Root-uptake of ethanol was metabolized to organic acids, nucleic acids, amines and other molecules, followed by an increase in putrescine content, which substantially promoted unfolded protein response (UPR) signaling and high-temperature acclimation. We also showed that inhibition of polyamine production and UPR signaling negated the heat stress tolerance induced by ethanol pretreatment. These findings collectively indicate that ethanol priming activates UPR signaling via putrescine accumulation, leading to enhanced heat stress tolerance. The information gained from this study will be useful for establishing ethanol-mediated chemical priming strategies that can be used to help maintain crop production under heat stress conditions. [ABSTRACT FROM AUTHOR]

Background: Exponentially increasing population and everchanging climatic conditions are two major concerns for global food security. Early sowing in the second fortnight of October is an emerging trend with farmers in Indo Gangetic Plains to avoid yield losses from terminal heat stress. This also benefits the use of residual soil moisture of rice crop, conserving about one irrigation. But most of the available wheat cultivars are not well adapted to early-season sowing. Methods and results: Two in-house developed SHWs, syn14128 and syn14170, were screened for juvenile heat stress. Seedling length, biochemical parameters, and expression of amylase gene immediately after heat shock (HS) of 45 °C for 12 h and 20 h, and 24 h indicated significantly lower malondialdehyde, hydrogen peroxide, and higher free radical scavenging activities. Syn14170 reported higher total soluble sugar (TSS) under both HS periods, while syn14128 had a sustainable TSS content and amylase activity under HS as well as the recovery period. Conclusions: Both the SHWs had lower oxidative damage along with high free radical scavenging under heat stress. The higher expression of amy4 along with sustainable TSS after heat stress in syn14128 indicated it as a potential source of juvenile heat stress tolerance. Variable response of SHWs to different biochemical parameters under heat stress opens future perspectives to explore the enzymatic pathways underlying these responses. [ABSTRACT FROM AUTHOR]

Increasing global temperature has adverse effects on crop health and productivity at both seedling and reproductivity stages. It is paramount to develop heat tolerant wheat cultivars able to sustain under high and fluctuating temperature conditions. An experiment was conducted to characterize 194 historical wheat cultivars of Pakistan under high temperature at seedling stage to identify loci associated with heat tolerance using genome-wide association studies (GWAS). A quantitative trait locus, TaHST1, on chr4A was also characterized to identify the haplotypes at this locus associated with heat tolerance in wheat from Pakistan. Initially, the diversity panel was planted under control conditions (25°C/20°C day and night temperature) in a glass house. At three leaf stage, plants were subjected to heat stress (HS) by increasing temperature (40°C/35°C day and night), while one treatment was kept at control condition. After 7 days of HS, data were collected for seedling morphology. Heat stress reduced these traits by 25% (root weight) to 40% (shoot weight), and shoot biomass was largely affected by heat stress. A GWAS model, fixed and random model circulating probability unification (FarmCPU), identified 43 quantitative trait nucleotides (QTNs) on all chromosomes, except chr7B, were associated under both HS and control conditions. Thirteen QTNs were identified in control, while 30 QTNs were identified in HS condition. In total, 24 haplotypes were identified at TaHST1 locus, and most of the heat tolerant genotypes were assigned to Hap-20 and Hap-21. Eleven QTNs were identified within 0.3–3.1 Mb proximity of heat shock protein (HSP). Conclusively, this study provided a detailed genetic framework of heat tolerance in wheat at the seedling stage and identify potential genetic regions associated with heat tolerance which can be used for marker assisted selection (MAS) in breeding for heat stress tolerance.

Meiosis is the least explored stage for thermotolerance in wheat. We evaluated the impact of 5 d of moderate transient daily heat stress during meiosis in the main stem spike on physiological and grain yield traits in 30 diverse wheat cultivars which vary widely in heat tolerance and sensitivity. We found that a moderate heat stress event during meiosis in the main stem spike had lasting impacts on plant growth and reproduction in heat-sensitive, but not heat-tolerant, wheat cultivars. Heat-tolerant cultivars maintained grain yield, grain number and individual grain weight in the main stem spike and also total plant grain yield and biomass in the heat stress treatment relative to the control. Heat-sensitive cultivars responded to heat stress by producing fewer and smaller grains per spikelet on the main stem, fewer tillers, lower biomass and lower total plant grain yield in the high temperature treatment relative to the control. Heat-sensitive cultivars produced higher flag leaf chlorophyll content in the high temperature treatment relative to the control than heat-tolerant cultivars during the first 3 d of heat treatment. There was small reduction in pollen viability from 98% to 96% following heat stress during meiosis which was unrelated to heat tolerance or sensitivity. Moderate transient heat stress during meiosis did not greatly reduce the production of viable male gametes, but had long-lasting negative impacts on fertilization and subsequent seed production in heat-sensitive cultivars. [ABSTRACT FROM AUTHOR]

Key message: Plant heat stress response is a multi-factorial trait that is precisely regulated by the complex web of transcription factors from various families that modulate heat stress responsive gene expression. Global warming due to climate change affects plant growth and development throughout its life cycle. Adds to this, the frequent occurrence of heat waves is drastically reducing the global crop yield. Molecular plant scientists can help crop breeders by providing genetic markers associated with stress resistance. Plant heat stress response (HSR), however, is a multi-factorial trait and using a single stress resistance trait might not be ideal to develop thermotolerant crops. Transcription factors participate in regulation of plant biological processes and environmental stress responses. Recent studies have revealed that plant HSR is precisely regulated by the complex web of transcription factors from various families. These transcription factors enhance plant heat stress tolerance by regulating the expression level of several stress-responsive genes independently or in cross talk with different other transcription factors. This review explores how signaling pathways triggered by heat stress are regulated by multiple transcription factor families. To our knowledge, we for the first time analyze the role of major transcription factor families in plant HSR along with their regulatory mechanisms. In the end, we will also discuss the potential of emerging technologies to improve thermotolerance in plants. [ABSTRACT FROM AUTHOR]

The enhancement of heat stress tolerance at anthesis is an important strategy to achieve sustainable rice production in the context of predicted global warming. In this study, we genetically analysed spikelet fertility under high temperature treatment (38°C) at anthesis using the three rice varieties, namely, Koshihikari and Takanari, which were developed in Japan, and IR64, which was developed in the Philippines. Genetic analysis of the F2 population between Takanari and IR64 revealed a quantitative trait locus (QTL) on chromosome 4 that increased spikelet fertility with the Takanari allele and that was likely qHTSF4.1, a previously fine-mapped major QTL. Genetic analysis using chromosome segment substitution lines (CSSLs) carrying Koshihikari chromosome segments in the IR64 genetic background did not show any QTLs. In contrast, genetic analysis using CSSLs carrying Koshihikari chromosome segments in the Takanari genetic background revealed some QTLs, including chromosomes 4 and 9. These results suggest that the expression of QTLs may depend on genetic background. The two CSSLs, SL1313 and SL1330, which carried the QTLs on chromosomes 4 and 9, respectively, exhibited a spikelet fertility of over 80% and relatively large anther dehiscence compared with Takanari. These results suggest that the Koshihikari allele of QTLs may be related to improved anther dehiscence, which may lead to successful pollination and ultimately increased spikelet fertility under heat stress conditions. The findings in the present study should be useful to enhance heat stress tolerance at anthesis in rice in future breeding programs.

Meta-QTL analysis for thermotolerance in wheat was conducted to identify robust meta-QTLs (MQTLs). In this study, 441 QTLs related to 31 heat-responsive traits were projected on the consensus map with 50,310 markers. This exercise resulted in the identification of 85 MQTLs with confidence interval (CI) ranging from 0.11 to 34.9 cM with an average of 5.6 cM. This amounted to a 2.96-fold reduction relative to the mean CI (16.5 cM) of the QTLs used. Seventy-seven (77) of these MQTLs were also compared and verified with the results of recent genome-wide association studies (GWAS). The 85 MQTLs included seven MQTLs that are particularly useful for breeding purposes (we called them breeders' MQTLs). Seven ortho-MQTLs between wheat and rice genomes were also identified using synteny and collinearity. The MQTLs were used for the identification of 1,704 candidate genes (CGs). In silico expression analysis of these CGs permitted identification of 182 differentially expressed genes (DEGs), which included 36 high confidence CGs with known functions previously reported to be important for thermotolerance. These high confidence CGs encoded proteins belonging to the following families: protein kinase, WD40 repeat, glycosyltransferase, ribosomal protein, SNARE associated Golgi protein, GDSL lipase/esterase, SANT/Myb domain, K homology domain, etc. Thus, the present study resulted in the identification of MQTLs (including breeders' MQTLs), ortho-MQTLs, and underlying CGs, which could prove useful not only for molecular breeding for the development of thermotolerant wheat cultivars but also for future studies focused on understanding the molecular basis of thermotolerance. [ABSTRACT FROM AUTHOR]

An increase in seawater temperature owing to global warming is expected to substantially limit the growth of marine algae, including Pyropia yezoensis, a commercially valuable red alga. To improve our knowledge of the genes involved in the acquisition of heat tolerance in P. yezoensis, transcriptomes sequences were obtained from both the wild-type SG104 P. yezoensis and heat-tolerant mutant Gy500. We selected 1,251 differentially expressed genes that were up- or downregulated in response to the heat stress condition and in the heat-tolerant mutant Gy500, based on fragment per million reads expression values. Among them, PyHRG1 was downregulated under heat stress in SG104 and expressed at a low level in Gy500. PyHRG1 encodes a secretory protein of 26.5 kDa. PyHRG1 shows no significant sequence homology with any known genes deposited in public databases to date. However, PyHRG1 homologs were found in other red algae, including other Pyropia species. When PyHRG1 was introduced into the single-cell green alga Chlamydomonas reinhardtii, transformed cells overexpressing PyHRG1 showed severely retarded growth. These results demonstrate that PyHRG1 encodes a novel red algae-specific protein and plays a role in heat tolerance in algae. The transcriptome sequences obtained in this study, which include PyHRG1, will facilitate future studies to understand the molecular mechanisms involved in heat tolerance in red algae. [ABSTRACT FROM AUTHOR]

In the present era of climate change and global warming, high temperatures have increased considerably, posing a threat to plant life. Heat stress affects the biochemistry, physiology and molecular makeup of the plant by altering the key processes, i.e., photosynthesis, respiration and reproduction which reduces its growth and development. There is a dire need to manage this problem sustainably for plant conservation as well as the food security of the human population. Use of phytohormones to induce thermotolerance in plants can be a sustainable way to fight the adversities of heat stress. Phytohormone-induced thermotolerance proves to be a compelling approach to sustainably relieve the damaging effects of heat stress on plants. Salicylic acid (SA) is an essential molecule in biotic and abiotic defense response signal transduction pathways. When supplied externally, it imparts heat stress tolerance to the plants by different means, viz., increased Heat Shock Proteins (HSP) production, Reactive oxygen species (ROS) scavenging, protection of the reproductive system and enhancing photosynthetic efficiency. The effect of SA on plants is highly dependent on the concentration applied, plant species, plant age, type of tissues treated, and duration of the treatment. The present review paper summarizes the mechanism of thermotolerance induced by salicylic acid in plants under heat stress conditions. It includes the regulatory effects of SA on heat shock proteins, antioxidant metabolism, and maintenance of Ca2+ homeostasis under heat stress. This review combines the studies conducted to elucidate the role of SA in the modulation of different mechanisms which lead to heat stress tolerance in plants. It discusses the mechanism of SA in protecting the photosynthetic machinery and reproductive system during high-temperature stress.

Summary: Heat stress (HS) causes substantial damages to worldwide crop production. As a cool season crop, wheat (Triticum aestivum) is sensitive to HS‐induced damages. To support the genetic improvement of wheat HS tolerance (HST), we conducted fine mapping of TaHST1, a locus required for maintaining wheat vegetative and reproductive growth under elevated temperatures. TaHST1 was mapped to the distal terminus of 4AL chromosome arm using genetic populations derived from two BC6F6 breeding lines showing tolerance (E6015‐4T) or sensitivity (E6015‐3S) to HS. The 4AL region carrying TaHST1 locus was approximately 0.949 Mbp and contained the last 19 high confidence genes of 4AL according to wheat reference genome sequence. Resequencing of E6015‐3S and E6015‐4T and haplotype analysis of 3087 worldwide wheat accessions revealed heightened deletion polymorphisms in the distal 0.949 Mbp region of 4AL, which was confirmed by the finding of frequent gene losses in this region in eight genome‐sequenced hexaploid wheat cultivars. The great majority (86.36%) of the 3087 lines displayed different degrees of nucleotide sequence deletions, with only 13.64% of them resembling E6015‐4T in this region. These deletions can impair the presence and/or function of TaHST1 and surrounding genes, thus rendering global wheat germplasm vulnerable to HS or other environmental adversities. Therefore, conscientious and urgent efforts are needed in global wheat breeding programmes to optimize the structure and function of 4AL distal terminus by ensuring the presence of TaHST1 and surrounding genes. The new information reported here will help to accelerate the ongoing global efforts in improving wheat HST. [ABSTRACT FROM AUTHOR]

Heat is a major abiotic stress that drastically reduces chickpea yield. This study aimed to identify heat-responsive traits to sustain crop productivity by screening a recombinant inbred line (RILs) population at two locations in India (Ludhiana and Faridkot). The RIL population was derived from an inter-specific cross between heat-tolerant genotype GPF 2 (C. arietinum L.) and heat sensitive accession ILWC 292 (C. reticulatum). The pooled analysis of variance showed highly significant differences for all the traits in RILs and most of the traits were significantly affected by heat stress at both locations. High values of genotypic coefficient of variation (19.52–38.53%), phenotypic coefficient of variation (20.29–39.85%), heritability (92.50–93.90%), and genetic advance as a percentage of mean (38.68–76.74%) have been observed for plant height, number of pods per plant, biomass, yield, and hundred seed weight across the heat stress environments. Association studies and principal component analysis showed a significant positive correlation of plant height, number of pods per plant, biomass, hundred seed weight, harvest index, relative leaf water content, and pollen viability with yield under both timely-sown and late-sown conditions. Path analysis revealed that biomass followed by harvest index was the major contributor to yield among the environments. Both step-wise and multiple regression analyses concluded that number of pods per plant, biomass and harvest index consistently showed high level of contribution to the total variation in yield under both timely-sown and late-sown conditions. Thus, the holistic approach of these analyses illustrated that the promising traits provide a framework for developing heat-tolerant cultivars in chickpea. [ABSTRACT FROM AUTHOR]

Abstract Transient daily heat stress during flowering of canola (Brassica napus L.) as a result of global warming is an increasing threat to grain production in this important oilseed crop. We investigated the intensity and duration of transient daily heat stress treatment at different stages of reproductive development in three B. napus genotypes under controlled environment conditions. Heat stress treatments during the week before first open flower on the main stem (S0) or during the first week (S1) or second week (S2) following first open flower greatly reduced pod number and seed yield on the main stem. Heat stress treatment during the third week (S3), fourth week (S4), or fifth week (S5) reduced seed yield more on the branches and less on the main stem as time progressed. Pod number and seed yield were reduced by moderate heat stress (TC2; 32°C/22°C) and high heat stress (TC3; 35°C/25°C), compared with the control (TC1, 25°C/15°C). Each duration of heat stress treatment (3, 5 or 7 days) caused the same reduction in pod number and seed per pod on the main stem. Leaf stomatal conductance, leaf chlorophyll index, plant height, and dry weight of above‐ground biomass increased from TC1 to TC3, which indicates that heat stress in the absence of drought stress does not inhibit vegetative growth. Cool night temperatures (15°C) resulted in recovery of pod number and seed yield after moderate (32°C) but not high (35°C) daily transient heat stress. The range of genotype responses to heat stress was greater under TC2 than under TC3. This research brings forward the critical period for heat stress sensitivity in B. napus to one week before first open flower and defines the conditions for controlled environment screening for heat tolerance in B. napus.

The impact of dietary regimens on productive traits, meat quality, physiological adoption, immunological response and digestibility of nutrients was studied using Ross-308 and Cobb-500 strains. Chickens were reared under normal brooding conditions during most of the experimental period, but exposed to heat stress [(HS); 32 °C and 55% RH] during 20–22 and 28–30 d of age. During 1–18 d of age, broilers were fed a standard-protein diet [(SPD); 22% crude protein (CP) with 12.97 MJ/kg], a high-protein diet [(HPD); 24% CP with 12.97 MJ/kg], or a high-protein with high-metabolisable energy (ME) diet [(HPMED); 24% CP with 13.60 MJ/kg]. During 19–35 d of age, the SPD group was fed 20% CP with 13.42 MJ/kg, the HPD group was fed 22% CP with 13.42 MJ/kg, and the HPMED group was fed 22% CP with 14.06 MJ/kg. Each group within each strain was replicated six times with five chicken males each. For the whole experimental period, Ross and Cobb chickens fed the HPMED showed higher BWG than chickens on the HPD. Broilers fed the HPMED had improved FCR compared to those on the SPD, independent of broiler strain. Further, independent of broiler strain, the HPMED regimen increased the dry matter, protein, and lipid contents of meat compared to the other regimens, and decreased cloacal temperature, respiration rate and Heterophile/lymphocyte (H/L ratio) compared to the HPD regimen. Growth and feed utilisation, percentage thymus, protein in meat were improved of Ross compared to Cobb, but abdominal fat, meat lipid and pH were decreased. On the other hand, Cobb on HPD had lower cloacal temperature and respiration rate than Ross strain, suggesting that production, physiology and immunological response of broiler chickens depend on feeding regimen that should be specific for each strain.

Transient daily heat stress during flowering of canola (Brassica napus L.) as a result of global warming is an increasing threat to grain production in this important oilseed crop. We investigated the intensity and duration of transient daily heat stress treatment at different stages of reproductive development in three B. napus genotypes under controlled environment conditions. Heat stress treatments during the week before first open flower on the main stem (S0) or during the first week (S1) or second week (S2) following first open flower greatly reduced pod number and seed yield on the main stem. Heat stress treatment during the third week (S3), fourth week (S4), or fifth week (S5) reduced seed yield more on the branches and less on the main stem as time progressed. Pod number and seed yield were reduced by moderate heat stress (TC2; 32°C/22°C) and high heat stress (TC3; 35°C/25°C), compared with the control (TC1, 25°C/15°C). Each duration of heat stress treatment (3, 5 or 7 days) caused the same reduction in pod number and seed per pod on the main stem. Leaf stomatal conductance, leaf chlorophyll index, plant height, and dry weight of above‐ground biomass increased from TC1 to TC3, which indicates that heat stress in the absence of drought stress does not inhibit vegetative growth. Cool night temperatures (15°C) resulted in recovery of pod number and seed yield after moderate (32°C) but not high (35°C) daily transient heat stress. The range of genotype responses to heat stress was greater under TC2 than under TC3. This research brings forward the critical period for heat stress sensitivity in B. napus to one week before first open flower and defines the conditions for controlled environment screening for heat tolerance in B. napus. [ABSTRACT FROM AUTHOR]

Climate change plays a key role in wheat production. The objective of this study was to identify and select efficient parents and cross combinations based on general and specific combining ability under different climatic conditions. Analysis of combining ability was carried out by Line × Tester mating design by crossing 10 lines and 5 testers resulting in 50 F1 hybrids. All of these 65 genotypes sown in the Randomized Complete Block Design (RCBD) in three replications during cropping season of 2015-16 in both normal and heat stress conditions. Significant genetic variation was observed for yield and related characters. The general combining ability (GCA) estimates revealed that parents naming SW89.5277, V-12103 and V-13248 showed excellent general combining ability for almost all of the traits study under both conditions. It was also found that the crosses i.e. V-13241 × Millat-11 for plant height, V-13248 × Millat-11 for spikelets per spike, V-13013 × Millat-11 for grains per spike, Shahkar-2013 × Chenab-2000 for thousand grain weight and Faisalabad-08 × V-12082 for grain yield per plant, exhibited good specific combining ability estimates under both conditions. The parents and crosses that exhibited excellent results in terms of GCA and SCA estimates may be exploited in improving the yield of crop and yield related characters against normal and heat stress conditions. [ABSTRACT FROM AUTHOR]

Cotton is severely affected by heat stress in most parts of Pakistan which results in poor quality and low cotton yield. Sixty cotton strains were screened against heat stress on the basis of cellular membrane thermostability, chlorophyll contents, canopy temperature, node number of first fruiting branch, boll weight and seed cotton yield to explore the genetics of variation among genotypes for heat tolerance. Five tolerant and five sensitive parents were sorted out and crossed in Line × Tester mating design during 2018.The F1 crosses along with parents were grown in field under normal and heat stress conditions by using two sowing dates to create heat stress in the field. Sowing during 1st week of April was considered as heat stressed because its peak flowering period was supposed to be coincided with the maximum temperature of May-June; while, sowing during 1st week of June was taken as normal because its peak flowering period coincided with normal temperature of August. Data regarding cell membrane themostability (CMT%), chlorophyll contents, canopy temperature, node number to first fruiting branch, bolls/plant, boll weight, ginning out turn and seed cotton yield under normal as well as heat stressed conditions were collected which showed significant differences among genotypes for all the traits under investigation. Most of the traits showed greater mean square for female × male interaction than female and male individual mean squares and higher dominance variance than additive variance. Broad sense heritability for investigated traits was observed in the order of boll weight (94.56), seed cotton yield (94.51), CMT% (91.88), canopy temperature (90.48), node number to first fruiting branch (75.68) and chlorophyll contents (51.93). FH-458 and PB-76 indicated high general combining ability for most of the traits whereas the cross combination FH-458× FH-326 was described as the best cross showing 56.85% better parent heterosis for seed cotton yield under heat stress conditions. The present study was planned to investigate the genetics of some important physiological and agronomic traits of cotton which is a pre-requisite for the development of high yielding cotton varieties under high temperature stress. [ABSTRACT FROM AUTHOR]

The enhancement of heat stress tolerance at anthesis is an important strategy to achieve sustainable rice production in the context of predicted global warming. In this study, we genetically analysed spikelet fertility under high temperature treatment (38°C) at anthesis using the three rice varieties, namely, Koshihikari and Takanari, which were developed in Japan, and IR64, which was developed in the Philippines. Genetic analysis of the F2 population between Takanari and IR64 revealed a quantitative trait locus (QTL) on chromosome 4 that increased spikelet fertility with the Takanari allele and that was likely qHTSF4.1, a previously fine-mapped major QTL. Genetic analysis using chromosome segment substitution lines (CSSLs) carrying Koshihikari chromosome segments in the IR64 genetic background did not show any QTLs. In contrast, genetic analysis using CSSLs carrying Koshihikari chromosome segments in the Takanari genetic background revealed some QTLs, including chromosomes 4 and 9. These results suggest that the expression of QTLs may depend on genetic background. The two CSSLs, SL1313 and SL1330, which carried the QTLs on chromosomes 4 and 9, respectively, exhibited a spikelet fertility of over 80% and relatively large anther dehiscence compared with Takanari. These results suggest that the Koshihikari allele of QTLs may be related to improved anther dehiscence, which may lead to successful pollination and ultimately increased spikelet fertility under heat stress conditions. The findings in the present study should be useful to enhance heat stress tolerance at anthesis in rice in future breeding programs. [ABSTRACT FROM AUTHOR]

There is increasing experimental evidence that strigolactones, a class of carotenoid-derived sesquiterpenoid hormones, and their downstream signal components play a role in plant resilience to abiotic stress. Strigolactones positively influence plant coping mechanisms in response to abiotic stressors like drought and high salinity. In this study, we examined the effects of rac- GR24 (a synthetic strigolactone analog) and strigolactone inhibitors on the physiological and molecular responses associated with thermotolerance during seed germination and seedling development in Lupinus angustifolius under heat stress. Photosystem I & II functions were also evaluated via Chl a fluorescence transient analysis in heat stressed lupine seedlings. Our results suggest a putative role for GR24 in mediating tolerance to heat stress during seed germination and seedling development albeit these responses appeared independent of D14-mediated signalling. Seeds primed with GR24 had the highest of all germination indices, enhanced proline content and reduced peroxidation of lipids. GR24 also enhanced the activities of enzymes of the antioxidant and glyoxalase systems in lupine seedlings. The JIP-test indicated that GR24 conferred resistance to heat stress-induced damage to the oxygen evolution complex while also preventing the inactivation of PSII reaction centres thus ensuring PSII thermotolerance. • Synthetic strigolactone (rac-GR24) in mediating resistance to heat stress in lupine seedlings. • Influence of GR24 on plant biochemical and glyoxalase system responses to heat stress. • GR24 confers a significant level of heat tolerance through a photosynthetic system. • The emerging role of strigolactones in coping mechanisms to abiotic stressors. [ABSTRACT FROM AUTHOR]

Genetic improvement along with widened crop base necessitates for the detailed understanding of the genetic diversity and population structure in wheat. The present investigation reports the discovery of a total of 182 alleles by assaying 52 simple sequence repeats (SSRs) on 40 genotypes of bread wheat. Unweighted neighbour-joining method grouped these genotypes into two main clusters. Highly heat tolerant and intermediate tolerant cultivars were grouped in the same cluster, whereas remaining genotypes, particularly sensitive ones, were assigned different cluster. Similarly, the entire population was structured into two sub-populations (K = 2), closely corresponding with the other distance-based clustering patterns. The marker-trait association was discovered for four important physiological parameters, viz. canopy temperature depression, membrane thermostability index (MSI), normalized difference vegetation index and heat susceptibility index, indicating for heat stress (HS) tolerance in wheat. Both general and mixed linear models of association studies during 2017 and 2018, revealed the association of SSR markers, wmc222 (17.60%, PV) and gwm34 (20.70%, PV) with the mean phenotypic value of MSI. Likewise, SSR markers barc183, gwm75, gwm11 and cfd7 revealed a unique relationship with four selected physiological traits. Candidate genes discovered using in silico tools had nine SSR markers within the genic regions reported to play a role in heat and drought stress responses in plants. The information generated about these genic regions may be explored further in expression studies in-vivo to impart HS tolerance in bread wheat. [ABSTRACT FROM AUTHOR]

Heat stress is an increasing threat to rice production worldwide. To investigate the mechanisms of heat tolerance in hybrid rice and their contributions to rice heterosis, we compared the transcriptome of the hybrid rice II YOU 838 (II8) with the transcriptomes of its parents Fu Hui 838 (F8) and II-32A (II3) after heat stress at 42 °C for 0 h, 24 h, 72 h and 120 h. We also performed a proteomic analysis in II8 after heat stress at 42 °C for 24 h. The transcriptome data revealed time-dependent gene expression patterns under the heat stress conditions, and the heat stress response of II8 was greatly different from those of its parents. Gene ontology analysis of the differentially expressed genes that were clustered using k-means clustering showed that most of the up-regulated genes were involved in responses to stimuli, cell communication, and metabolic and transcription factor activities, whereas the down-regulated genes were enriched in photosynthesis and signal transduction. Moreover, 35 unique differentially abundant proteins, including a basic helix-loop-helix transcription factor (bHLH96), calmodulin-binding transcription activator, heat shock protein (Hsp70), and chaperonin 60 (CPN60), were detected in the proteomic analysis of II8 under heat stress. The co-regulatory analysis revealed novel genes and pathways involved in heat tolerance, namely, ferredoxin-NADP reductase, peroxidases, mitogen-activated protein kinase kinase kinase, and heat shock factor (HSF)–Hsp network. Members of the Hsp and HSF families had over-dominant expression patterns in the hybrid compared with its parents, to help maintain the higher photosynthesis and antioxidant defense systems in the hybrid. Our study suggests that the complex HSF–Hsp regulatory network contribute to the heat tolerance of the hybrid rice.

Premise: Divergence in functional traits and adaptive responses to environmental change underlies the ecological advantage of polyploid plants in the wild. While established polyploids may benefit from combined outcomes of genome doubling, hybridization, and polyploidy‐enabled adaptive evolution, whether genome doubling alone can drive ecological divergence or whether the outcome is genetically variable remains less clear. Methods: Using synthetic, colchicine‐induced, autotetraploid (4x) plants derived from self‐pollinated diploid (2x) seeds, and their colchicine‐treated but unconverted diploid (2x.nc) full sibs from two diploid wild strawberry taxa (Fragaria vesca subsp. vesca and F. vesca subsp. bracteata), we examined the effects of genome doubling on functional traits, heat stress tolerance, and fitness components across taxa and maternal families (i.e., genetic families) within taxa. Results: Comparisons between 2x and 2x.nc plants indicated a negligible effect of colchicine treatment on functional traits. Genome doubling increased stomatal length and decreased stomatal density, specific leaf area, and leaf vein density, recapitulating patterns observed in wild polyploid Fragaria. Trichome density, heat stress tolerance, and relative growth rate were not significantly affected by genome doubling. Although clonal reproduction was reduced in response to genome doubling, this effect was strongly genetic‐family dependent. Conclusions: The results suggest that genome doubling during incipient speciation alone can generate ecological divergence and variation among genetic lineages. This response potentially allows for rapid short‐term evolutionary adaptation and fuels genomic diversity and independent origins of polyploidy. [ABSTRACT FROM AUTHOR]

Anti-oxidative system in plants comprising of enzymatic and non-enzymatic antioxidants imparts stress tolerance by scavenging/detoxification of excess reactive oxygen species (ROS) produced under high temperature stress. Present investigation deals with the estimation of metabolites and anti-oxidative enzyme activities in four inbred maize lines; NSJ221, NSJ189, PSRJ13099 and RJR270 in response to high temperature stress imposed at reproductive stage by staggered sowing. An increase in H2O2 and malondialdehyde (MDA) was observed in all the genotypes, however the increase was higher in PSRJ13099 and RJR270. The activities of studied enzymes increased in NSJ189 and NSJ221 while a decrease was observed in PSRJ13099 and RJR270. Under heat stress isoforms of SOD increased in NSJ189 and NSJ221 while a concomitant decrease was observed in PSRJ13099 and RJR270. Two new SOD-isoforms were also observed in NSJ221. GPX showed more number of high mobility isoforms with low activity in NSJ221 and less mobile isoforms with higher activity in both NSJ189 and NSJ221. Whereas, PSRJ13099 and RJR270 showed decrease band intensity of less mobile GPX-isoforms under heat stress. Activity of CAT-isoforms increased to a similar extent across the genotypes under heat stress. In case of non-enzymatic antioxidants, non-protein thiols increased in all the genotypes while the level of carotenoids depleted in all the genotypes except NSJ221. Ascorbate (AsA) levels depleted in PSRJ13099 and RJR270 and increased in NSJ189 and NSJ221 under heat stress. Understanding the intricate regulatory pathways in crop plants under heat stress will help in developing genotypes with enhanced stress tolerance. [ABSTRACT FROM AUTHOR]

Rice kefiran is superior in functionality, has high concentration of mucilaginous polysaccharide, and low lipid content, compared to conventional kefiran. However, reports on its physiological functionality, especially studies on life expectancy and aging, in model organisms are rare. In this study, nematodes were used as model organisms that were fed rice kefiran, along with Escherichia coli OP50, as a result of which, the lifespan of nematodes was extended and age-related retardation of mobility was suppressed. It also increased the heat stress resistance in nematodes. Experiments using daf-16 deletion mutant revealed that rice kefiran functions via DAF-16. Thus, this study revealed the longevity, anti-aging and heat stress tolerance effects of rice kefiran in nematodes. Rice kefiran fed C. elegans prolonged life span, increased motility and enhanced heat stress tolerance. These anti-aging effects was mediated through DAF-16. [ABSTRACT FROM AUTHOR]

Rapamycin is a powerful inhibitor of the TOR (Target of Rapamycin) pathway, which is an evolutionarily conserved protein kinase, that plays a central role in plants and animals. Rapamycin is used globally as an immunosuppressant and as an anti-aging medicine. Despite widespread use, treatment efficiency varies considerably across patients, and little is known about potential side effects. Here we seek to investigate the effects of rapamycin by using Drosophila melanogaster as model system. Six isogenic D. melanogaster lines were assessed for their fecundity, male longevity and male heat stress tolerance with or without rapamycin treatment. The results showed increased longevity and heat stress tolerance for male flies treated with rapamycin. Conversely, the fecundity of rapamycin-exposed individuals was lower than for flies from the non-treated group, suggesting unwanted side effects of the drug in D. melanogaster. We found strong evidence for genotype-by-treatment interactions suggesting that a ‘one size fits all’ approach when it comes to treatment with rapamycin is not recommendable. The beneficial responses to rapamycin exposure for stress tolerance and longevity are in agreement with previous findings, however, the unexpected effects on reproduction are worrying and need further investigation and question common believes that rapamycin constitutes a harmless drug.

It is known that regulation of plant tolerance to adverse environmental factors is connected with short term increase of the concentration of endogenous reactive oxygen species (ROS), which are signalling molecules for the induction of protective mechanisms. Introduction and expression of heterologous gox gene, which encodes glucose oxidase enzyme in plant genome, induce constantly higher content of hydrogen peroxide in plant tissues. It is not known how the introduction of native or modified gox gene affects the plant resistance to high-temperature stress, one of the most commonly used model for the study of stress response and thermal tolerance. In this study, we investigated biological effects of transformation and evaluated the resistance to temperature stress of potato plants with altered levels of glucose oxidase expression. Transformation of potato plants by gox gene led to the more early coming out from tuber dormancy of transformed plants and slower growth rate. Transformants containing the glucose oxidase gene were more sensitive to lethal thermal shock (50 °C, 90 min) than the transformant with the empty vector (pBI) or untransformed plants (CK). Pre-heating of plants at 37 °C significantly weakened the damaging effect of lethal thermal shock. This attenuation was more significant in the non-transformed plants.

Rising temperature is among the most remarkably stressful phenomena induced by global climate changes with negative impacts on crop productivity and quality. It has been previously shown that volatiles belonging to the isoprenoid family can confer protection against abiotic stresses. In this work, two Vitis vinifera cv. ‘Chardonnay’ clones (SMA130 and INRA809) differing due to a mutation (S272P) of the DXS gene encoding for 1-deoxy-D-xylulose-5-phosphate (the first dedicated enzyme of the 2C-methyl-D-erythritol-4-phosphate (MEP) pathway) and involved in the regulation of isoprenoids biosynthesis were investigated in field trials and laboratory experiments. Leaf monoterpene emission, chlorophyll fluorescence and gas-exchange measurements were assessed over three seasons at different phenological stages and either carried out in in vivo or controlled conditions under contrasting temperatures. A significant (p < 0.001) increase in leaf monoterpene emission was observed in INRA809 when plants were experiencing high temperatures and over two experiments, while no differences were recorded for SMA130. Significant variation was observed for the rate of leaf CO2 assimilation under heat stress, with INRA809 maintaining higher photosynthetic rates and stomatal conductance values than SMA130 (p = 0.003) when leaf temperature increased above 30 °C. At the same time, the maximum photochemical quantum yield of PSII (Fv/Fm) was affected by heat stress in the non-emitting clone (SMA130), while the INRA809 showed a significant resilience of PSII under elevated temperature conditions. Consistent data were recorded between field seasons and temperature treatments in controlled environment conditions, suggesting a strong influence of monoterpene emission on heat tolerance under high temperatures. This work provides further insights on the photoprotective role of isoprenoids in heat-stressed Vitis vinifera, and additional studies should focus on unraveling the mechanisms underlying heat tolerance on the monoterpene-emitter grapevine clone.

Abstract The aim of this study was to determine the influence of different heat treatments on the alternative cyanide-resistant oxidase (AOX) capacity and establish a relation between the heat stress tolerance of spring wheat (Triticum aestivum L.), content of water-soluble carbohydrates in leaves and the alternative respiratory pathway (AP) capacity. We identified a positive relation between these studied parameters. Heat exposure at 39 °C for 24 h increased the heat stress tolerance of seedlings, content of water-soluble carbohydrates and AOX capacity, and the AOX capacity was also high after the subsequent influence of heat shock (50 °C for 3 h). The increased AOX capacity correlated with an increased level of water-soluble carbohydrates in leaves. The content of the AOX protein increased after heat exposure at 39 °C (for 3 h and 24 h) and after the subsequent influence of heat shock (50 °C for 1 and 3 h) at 39 °C for 24 h. We also detected that the content of AOX protein isoforms depends on the duration and intensity of heat treatment. It was concluded that AOX plays an important role in the acclimation of plants to high temperatures. [ABSTRACT FROM AUTHOR]

Highlights • A newly isolated rhizobacterium Bacillus licheniformis strain CH102 produced both diffusible and volatile antimicrobial compounds. • CH102 exerted effects on root architecture, leaf growth, antioxidant activity, and tolerance against heat and water deficit stresses. • CH102 activated Arabidopsis genes associated with biosynthesis of osmoprotectants including choline, proline, and galactinol. • Arabidopsis genes associated with the jasmonic acid and abscisic acid signaling pathways showed stronger effects with CH102. • Arabidopsis transcription factors including DDF2 , CBF1 , DREB2A , HSFA2 , WRKY30 and WRKY33 were subjected to the regulation of CH102. Abstract Plant-growth-promoting rhizobacteria play a beneficial role in plant growth through various mechanisms. In this study, an isolated rhizobacterial strain, Bacillus licheniformis CH102 (hereafter CH102), exhibited antifungal activity and harbored genes required for lantibiotic and 2,3-butanediol production. In Arabidopsis , increased root hair number and fresh weight were obtained in the CH102-inoculated seedlings. Moreover, increases in chlorophyll content, H 2 O 2 concentration and activities of antioxidant enzymes including catalase and POD were observed in the treated seedlings. Exposure to CH102 increased the tolerance toward high temperatures and water deficits in Arabidopsis seedlings. CH102 induced gene expression involved in induced disease resistance, nitrogen assimilation, antioxidants, photosystem II, ion transport and synthesis of secondary metabolites. Arabidopsis transcriptomic analysis revealed the CH102-upregulated genes were associated with several cellular pathways including the PEP-PEPR system, cell wall modification, and biosynthesis of osmoprotectants including choline, proline, and galactinol. The presence of CH102 elicited increased response of Arabidopsis genes associated with the jasmonic acid (JA) and abscisic acid (ABA) signaling pathways. Moreover, the upregulated expression of SLAC1 HOMOLOGUE 3 ( SLAH3 ) function in the regulation of stomatal closure was detected. Furthermore, CH102 inoculation increased expression of transcription factors implicated in the regulation of abiotic stress responses, including DDF2 , CBF1 , DREB2A , HSFA2 , WRKY30 and WRKY33. In summary, CH102 exerts effects on multiple cellular pathways involved in defense response, metabolism, antioxidant system and hormone signaling such as JA and ABA to regulate plant growth and tolerance to heat and drought stress. [ABSTRACT FROM AUTHOR]

The growing volatility of the climate, and its potential impact on crop production, has prompted several physiologic and genetic analyses under hightemperature conditions. Tomato is grown in warm temperate, subtropical, and tropical regions of the world, where daytime and nighttime temperatures regularly exceed the optimum temperatures for tomato growth during the summer, exerting stress on tomato production. Recent trends indicate more frequent extreme summer temperatures, which may grow even greater in the future, impacting crop growth. The objective of the current study was to estimate the heritability of flower and fruit set ability of tomato populations under heat stress conditions so that improvement for these traits can be planned. We developed two tomato populations using contrasting parents from the North Carolina State University (NCSU) tomato breeding program and the World Vegetable Center (formerly Asian Vegetable Research and Development Center). The F2 and F2-derived F3 families (F2:3 populations) were grown at the Piedmont Research Station (PRS), Salisbury, NC, where summer growing temperatures are warmer than optimum for tomato production. Heritability estimates of the number of flowers per cluster, the number of fruit per cluster, and fruit set (measured as a percentage) were determined in two populations of tomato--NC10137 (NC7143CLN-2413A) and NC10418 [230 HS-1(99)3 NC 1CS]--by regression analysis using the offspring-on-parents method. Broad-sense heritability across the traits was high (47.2%--100%), whereas narrow-sense heritability was very low (1.4%--22.5%). There was a positive correlation between the number of flowers and the number of fruit per cluster (r = 0.50, P < 0.05), which was in close agreement with previous findings. These findings will be useful in investigating the genetic control of heat stress tolerance in tomato and in facilitating crop improvement in the future. [ABSTRACT FROM AUTHOR]