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SUMMARY The protein levels of chloroplast photosynthetic genes and genes related to the chloroplast genetic apparatus vary to adapt to different conditions. However, the underlying mechanisms governing these variations remain unclear. The chloroplast intron Maturase K is encoded within the trnK intron and has been suggested to be required for splicing several group IIA introns, including the trnK intron. In this study, we used RNA immunoprecipitation followed by high‐throughput sequencing (RIP‐Seq) to identify MatK's preference for binding to group IIA intron domains I and VI within target transcripts. Importantly, these domains are crucial for splice site selection, and we discovered alternative 5′‐splice sites in three MatK target introns. The resulting alternative trnK lariat structure showed increased accumulation during heat acclimation. The cognate codon of tRNA‐K(UUU) is highly enriched in mRNAs encoding ribosomal proteins and a trnK‐matK over‐expressor exhibited elevated levels of the spliced tRNA‐K(UUU). Ribosome profiling analysis of the overexpressor revealed a significant up‐shift in the translation of ribosomal proteins compared to photosynthetic genes. Our findings suggest the existence of a novel regulatory mechanism linked to the abundance of tRNA‐K(UUU), enabling the differential expression of functional chloroplast gene groups. [ABSTRACT FROM AUTHOR]

Vertical oxidation pond operated in sequencing batch mode (HRT: 1.25 day) with duckweed as the vegetation was used to acclimatize with simulated agricultural wastewater. The maximum removal rate of urea [371 g/(m3.d)] and COD [222.4 g/(m3.d)] were observed at moderate concentrations of urea (500 mg/L), N-P-K (60 mg/L), and pesticide (20 mg/L). Inhibition and toxicity posed by higher concentrations, decreased the removals of urea (83% to 61%), COD (81% to 51%), and TDS (76% to 50%) at the end of the acclimatization. Steady removal (> 99%) of PO43−-P was observed during acclimatization. Effluent pH increased due to the generation of NH4+-N (maximum 370 ± 5 mg/L) from the assimilation of urea. Oxidation of ammonia led to the maximum generation of NO2−-N and NO3−-N of 10 mg/L and 9 mg/L, respectively. Particles less than 300 μm increased, and both specific gravity (from 2.62 to 2.42) and maximum dry density (from 1.73 to 1.30 g/cm3) of the base soil decreased with an increase in urea, N-P-K, and pesticide. Reactor biomass increased (1.42 to 1.90 g/L) up to initial concentrations of urea (500 mg/L), N-P-K (60 mg/L), and pesticide (20 mg/L), then decreased (1.68 g/L) with an increase in concentration. [ABSTRACT FROM AUTHOR]

Understanding photosynthetic acclimation to elevated CO2 (eCO2) is important for predicting plant physiology and optimizing management decisions under global climate change, but is underexplored in important horticultural crops. We grew three crops differing in stomatal density—namely chrysanthemum, tomato, and cucumber—at near‐ambient CO2 (450 μmol mol−1) and eCO2 (900 μmol mol−1) for 6 weeks. Steady‐state and dynamic photosynthetic and stomatal conductance (gs) responses were quantified by gas exchange measurements. Opening and closure of individual stomata were imaged in situ, using a novel custom‐made microscope. The three crop species acclimated to eCO2 with very different strategies: Cucumber (with the highest stomatal density) acclimated to eCO2 mostly via dynamic gs responses, whereas chrysanthemum (with the lowest stomatal density) acclimated to eCO2 mostly via photosynthetic biochemistry. Tomato exhibited acclimation in both photosynthesis and gs kinetics. eCO2 acclimation in individual stomatal pore movement increased rates of pore aperture changes in chrysanthemum, but such acclimation responses resulted in no changes in gs responses. Although eCO2 acclimation occurred in all three crops, photosynthesis under fluctuating irradiance was hardly affected. Our study stresses the importance of quantifying eCO2 acclimatory responses at different integration levels to understand photosynthetic performance under future eCO2 environments. [ABSTRACT FROM AUTHOR]

The photosynthetic acclimation of boreal evergreen conifers is controlled by regulatory and photoprotective mechanisms that allow conifers to cope with extreme environmental changes. However, the underlying dynamics of photosystem II (PSII) and photosystem I (PSI) remain unresolved. Here, we investigated the dynamics of PSII and PSI during the spring recovery of photosynthesis in Pinus sylvestris and Picea abies using a combination of chlorophyll a fluorescence, P700 difference absorbance measurements, and quantification of key thylakoid protein abundances. In particular, we derived a new set of PSI quantum yield equations, correcting for the effects of PSI photoinhibition. Using the corrected equations, we found that the seasonal dynamics of PSII and PSI photochemical yields remained largely in balance, despite substantial seasonal changes in the stoichiometry of PSII and PSI core complexes driven by PSI photoinhibition. Similarly, the previously reported seasonal up-regulation of cyclic electron flow was no longer evident, after accounting for PSI photoinhibition. Overall, our results emphasize the importance of considering the dynamics of PSII and PSI to elucidate the seasonal acclimation of photosynthesis in overwintering evergreens. Beyond the scope of conifers, our corrected PSI quantum yields expand the toolkit for future studies aimed at elucidating the dynamic regulation of PSI. [ABSTRACT FROM AUTHOR]

Climate change is swiftly altering environmental winter conditions, leading to significant ecological impacts such as phenological shifts in many species. As a result, animals might face physiological mismatches due to longer or earlier activity periods and are at risk of being exposed to late spring freezes. Our study points for the first time to the complex physiological challenges that amphibians face as a result of changing thermal conditions due to winter climate change. We investigated the physiological responses to a period of warmer winter days and sudden spring freeze in the common toad (Bufo bufo) by acclimating them to 4°C or 8°C for 48 h or exposing them to 4°C or −2°C for 6 h, respectively. We assessed the daily energy demands, determined body condition and cold tolerance, explored the molecular responses to freezing through hepatic tissue transcriptome analysis, and measured blood glucose levels. Toads acclimated to higher temperatures showed a higher daily energy expenditure and a reduced cold tolerance suggesting faster depletion of energy stores and the loss of winter acclimation during warmer winters. Blood sugar levels were higher in frozen toads indicating the mobilization of cryoprotective glucose with freezing which was further supported by changed patterns in proteins related to glucose metabolism. Overall, our results emphasize that increased thermal variability incurs physiological costs that may reduce energy reserves and thus affect amphibian health and survival. This might pose a serious threat to breeding adults and may have subsequent effects at the population level. [ABSTRACT FROM AUTHOR]

The plasticity of the xylem and its associated hydraulic properties play crucial roles in plant acclimation to environmental changes, with vessel diameter (Dv) being the most functionally prominent trait. While the effects of external environmental factors on xylem formation and Dv are not fully understood, the endogenous hormones indole‐3‐acetic acid (IAA) and abscisic acid (ABA) are known to play significant signalling roles under stress conditions. This study investigates how these hormones impact Dv under various environmental changes. Experiments were conducted in maize plants subjected to drought, soil salinity, and high CO2 concentration treatments. We found that drought and soil salinity significantly reduced Dv at the same stem internode, while an elevated CO2 concentration can mitigate this decrease in Dv. Remarkably, significant negative correlations were observed between Dv and the contents of IAA and ABA when considering the different treatments. Moreover, appropriate foliar application of either IAA or ABA on well‐watered and stressed plants led to a decrease in Dv, while the application of corresponding inhibitors resulted in an increase in Dv. This finding underscores the causal relationship between Dv and the levels of both IAA and ABA, offering a promising approach to manipulating xylem vessel size. [ABSTRACT FROM AUTHOR]

Plants have evolved various mechanisms to adapt to the ever‐changing external environment. Autophagy is one such mechanism and has been suggested to play a key role in responding to and adapting to abiotic stresses in plants. However, the role of autophagy in adaptation to cold and freezing stresses remains to be characterized in detail. Here, we investigated the role of autophagy in the low‐temperature response of Arabidopsis using atg mutants. Both the atg5‐1 and atg10‐1 mutants exhibited normal freezing tolerance, regardless of cold acclimation. A comparison of fresh weights indicated that the difference in growth between the wild‐type and atg plants under cold conditions was rather small compared with that under normal conditions. Analysis of COLD‐REGULATED gene expression showed no significant differences between the atg mutants and wild type. Treatment with 3‐methyladenine, an inhibitor of autophagy, did not impair the induction of COR15Apro::LUC expression upon exposure to low temperature. Evaluation of autophagic activity using transgenic plants expressing RBCS‐mRFP demonstrated that autophagy was rarely induced by cold exposure, even in the dark. Taken together, these data suggest that autophagy is suppressed by low temperatures and is dispensable for cold acclimation and freezing tolerance in Arabidopsis. [ABSTRACT FROM AUTHOR]

Maximal sunlight intensity varies diurnally due to the earth's rotation. Whether this slow diurnal pattern influences the photoprotective capacity of plants throughout the day is unknown. We investigated diurnal variation in NPQ, along with NPQ capacity, induction, and relaxation kinetics after transitions to high light, in tomato plants grown under diurnal parabolic (DP) or constant (DC) light intensity regimes. DP light intensity peaked at midday (470 μmol m‐2 s‐1) while DC stayed constant at 300 μmol m‐2 s‐1 at a similar 12‐hour photoperiod and daily light integral. NPQs were higher in the morning and afternoon at lower light intensities in DP compared to DC, except shortly after dawn. NPQ capacity increased from midday to the end of the day, with higher values in DP than in DC. At high light ΦPSII did not vary throughout the day, while ΦNPQ varied consistently with NPQ capacity. Reduced ΦNO suggested less susceptibility to photodamage at the end of the day. NPQ induction was faster at midday than at the start of the day and in DC than in DP, with overshoot occurring in the morning and midday but not at the end of the day. NPQ relaxation was faster in DP than in DC. The xanthophyll de‐epoxidation state and reduced demand for photochemistry could not explain the observed diurnal variations in photoprotective capacity. In conclusion, this study showed diurnal variation in regulated photoprotective capacity at moderate growth light intensity, which was not explained by instantaneous light intensity or increasing photoinhibition over the day and was influenced by acclimation to constant light intensity. [ABSTRACT FROM AUTHOR]

Phenotypic plasticity can buffer organisms against short‐term environmental fluctuations. For example, previous exposure to increased temperatures can increase thermal tolerance in many species. Prior studies have found that acclimation to higher temperature can influence the magnitude of transcriptional response to subsequent acute thermal stress (hereafter, "transcriptional response modulation"). However, mechanisms mediating this gene expression response and, ultimately, phenotypic plasticity remain largely unknown. Epigenetic modifications are good candidates for modulating transcriptional response, as they broadly correlate with gene expression. Here, we investigate changes in DNA methylation as a possible mechanism controlling shifts in gene expression plasticity and thermal acclimation in the reef‐building coral Acropora nana. We find that gene expression response to acute stress is altered in corals acclimated to different temperatures, with many genes exhibiting a dampened response to heat stress in corals pre‐conditioned to higher temperatures. At the same time, we observe shifts in methylation during both acclimation (11 days) and acute heat stress (24 h). We observed that the acute heat stress results in shifts in gene‐level methylation and elicits an acute transcriptional response in distinct gene sets. Further, acclimation‐induced shifts in gene expression plasticity and differential methylation also largely occur in separate sets of genes. Counter to our initial hypothesis no overall correlation between the magnitude of differential methylation and the change in gene expression plasticity. We do find a small but statistically significant overlap in genes exhibiting both dampened expression response and shifts in methylation (14 genes), which could be candidates for further inquiry. Overall, our results suggest transcriptional response modulation occurs independently from methylation changes induced by thermal acclimation. [ABSTRACT FROM AUTHOR]

The role of phenotypic plasticity during colonization remains unclear due to the shifting importance of plasticity across timescales. In the early stages of colonization, plasticity can facilitate persistence in a novel environment; but over evolutionary time, processes such as genetic assimilation may reduce variation in plastic traits such that species with a longer evolutionary history in an environment can show lower levels of plasticity than recent invaders. Therefore, comparing species in the early stages of colonization to long‐established species provides a powerful approach for uncovering the role of phenotypic plasticity during different stages of colonization. We compared gene expression between low‐dissolved oxygen (DO) and high‐DO populations of two cyprinid fish: Enteromius apleurogramma, a species that has undergone a recent range expansion, and E. neumayeri, a long‐established native species in the same region. We sampled tissue either immediately after capture from the field or after a 2‐week acclimation under high‐DO conditions, allowing us to test for both evolved and plastic differences in low‐DO vs high‐DO populations of each species. We found that most genes showing candidate‐evolved differences in gene expression did not overlap with those showing plastic differences in gene expression. However, in the genes that did overlap, there was counter‐gradient variation such that plastic and evolved gene expression responses were in opposite directions in both species. Additionally, E. apleurogramma had higher levels of plasticity and evolved divergence in gene expression between field populations. We suggest that the higher level of plasticity and counter‐gradient variation may have allowed rapid genetic adaptation in E. apleurogramma and facilitated colonization. This study shows how counter‐gradient variation may impact the colonization of divergent oxygen environments. [ABSTRACT FROM AUTHOR]

High altitude (HA) ascent imposes systemic hypoxia and associated risk of acute mountain sickness. Acute hypoxia elicits a hypoxic ventilatory response (HVR), which is augmented with chronic HA exposure (i.e., ventilatory acclimatization; VA). However, laboratory‐based HVR tests lack portability and feasibility in field studies. As an alternative, we aimed to characterize area under the curve (AUC) calculations on Fenn diagrams, modified by plotting portable measurements of end‐tidal carbon dioxide (PETCO2${P_{{\mathrm{ETC}}{{\mathrm{O}}_{\mathrm{2}}}}}$) against peripheral oxygen saturation (SpO2${S_{{\mathrm{p}}{{\mathrm{O}}_{\mathrm{2}}}}}$) to characterize and quantify VA during incremental ascent to HA (n = 46). Secondarily, these participants were compared with a separate group following the identical ascent profile whilst self‐administering a prophylactic oral dose of acetazolamide (Az; 125 mg BID; n = 20) during ascent. First, morning PETCO2${P_{{\mathrm{ETC}}{{\mathrm{O}}_{\mathrm{2}}}}}$ and SpO2${S_{{\mathrm{p}}{{\mathrm{O}}_{\mathrm{2}}}}}$ measurements were collected on 46 acetazolamide‐free (NAz) lowland participants during an incremental ascent over 10 days to 5160 m in the Nepal Himalaya. AUC was calculated from individually constructed Fenn diagrams, with a trichotomized split on ranked values characterizing the smallest, medium, and largest magnitudes of AUC, representing high (n = 15), moderate (n = 16), and low (n = 15) degrees of acclimatization. After characterizing the range of response magnitudes, we further demonstrated that AUC magnitudes were significantly smaller in the Az group compared to the NAz group (P = 0.0021), suggesting improved VA. These results suggest that calculating AUC on modified Fenn diagrams has utility in assessing VA in large groups of trekkers during incremental ascent to HA, due to the associated portability and congruency with known physiology, although this novel analytical method requires further validation in controlled experiments. Highlights: What is the central question of this study?What are the characteristics of a novel methodological approach to assess ventilatory acclimatization (VA) with incremental ascent to high altitude (HA)?What is the main finding and its importance?Area under the curve (AUC) magnitudes calculated from modified Fenn diagrams were significantly smaller in trekkers taking an oral prophylactic dose of acetazolamide compared to an acetazolamide‐free group, suggesting improved VA. During incremental HA ascent, quantifying AUC using modified Fenn diagrams is feasible to assess VA in large groups of trekkers with ascent, although this novel analytical method requires further validation in controlled experiments. [ABSTRACT FROM AUTHOR]

SUMMARY: Much progress has been made in understanding the molecular mechanisms of plant adaptation to heat stress. However, the great diversity of models and stress conditions, and the fact that analyses are often limited to a small number of approaches, complicate the picture. We took advantage of a liquid culture system in which Arabidopsis seedlings are arrested in their development, thus avoiding interference with development and drought stress responses, to investigate through an integrative approach seedlings' global response to heat stress and acclimation. Seedlings perfectly tolerate a noxious heat shock (43°C) when subjected to a heat priming treatment at a lower temperature (38°C) the day before, displaying a thermotolerance comparable to that previously observed for Arabidopsis. A major effect of the pre‐treatment was to partially protect energy metabolism under heat shock and favor its subsequent rapid recovery, which was correlated with the survival of seedlings. Rapid recovery of actin cytoskeleton and mitochondrial dynamics were another landmark of heat shock tolerance. The omics confirmed the role of the ubiquitous heat shock response actors but also revealed specific or overlapping responses to priming, heat shock, and their combination. Since only a few components or functions of chloroplast and mitochondria were highlighted in these analyses, the preservation and rapid recovery of their bioenergetic roles upon acute heat stress do not require extensive remodeling of the organelles. Protection of these organelles is rather integrated into the overall heat shock response, thus allowing them to provide the energy required to elaborate other cellular responses toward acclimation. Significance Statement: With increasing heat waves, we need to understand the mechanisms of acclimation. Using Arabidopsis seedlings, we show that the partial protection of respiration and photosynthesis and their rapid recovery upon heat shock induced by heat priming are primordial for survival. This does not require extensive remodeling in mitochondria and chloroplasts, the energy‐transducing organelles. It is rather integrated within the ubiquitous heat shock response, allowing energy production for other mechanisms required to fulfill acclimation. [ABSTRACT FROM AUTHOR]

SUMMARY: Plant acclimation to an ever‐changing environment is decisive for growth, reproduction, and survival. Light availability limits biomass production on both ends of the intensity spectrum. Therefore, the adjustment of plant metabolism is central to high‐light (HL) acclimation, and the accumulation of photoprotective anthocyanins is commonly observed. However, mechanisms and factors regulating the HL acclimation response are less clear. Two Arabidopsis mutants of spliceosome components exhibiting a pronounced anthocyanin overaccumulation in HL were isolated from a forward genetic screen for new factors crucial for plant acclimation. Time‐resolved physiological, transcriptome, and metabolome analysis revealed a vital function of the spliceosome components for rapidly adjusting gene expression and metabolism. Deficiency of INCREASED LEVEL OF POLYPLOIDY1 (ILP1), NTC‐RELATED PROTEIN1 (NTR1), and PLEIOTROPIC REGULATORY LOCUS1 (PRL1) resulted in a marked overaccumulation of carbohydrates and strongly diminished amino acid biosynthesis in HL. While not generally limited in N‐assimilation, ilp1, ntr1, and prl1 showed higher glutamate levels and reduced amino acid biosynthesis in HL. The comprehensive analysis reveals a function of the spliceosome components in the conditional regulation of the carbon:nitrogen balance and the accumulation of anthocyanins during HL acclimation. The importance of gene expression, metabolic regulation, and re‐direction of carbon towards anthocyanin biosynthesis for HL acclimation are discussed. Significance Statement: Spliceosomal components are required for high‐light acclimation. [ABSTRACT FROM AUTHOR]

The Arctic is impacted by some of the fastest temperature changes observed on Earth, but the impact on the terrestrial arthropod fauna is unclear. Acute physiological thermal limits of terrestrial ectotherms from high latitudes often exceed the local air temperatures, suggesting that they may be able to cope with increasing temperatures. However, knowledge on how Arctic terrestrial arthropods cope with elevated temperatures for longer periods is lacking.Here we investigate how acclimation temperature and exposure time affect the acute physiological heat tolerance of five terrestrial arthropod species (Neomolgus littoralis, Megaphorura arctica, Nysius groenlandicus, Psammotettix lividellus and Nabis flavomarginatus) immediately after collection in Arctic and sub‐Arctic habitats.We show that although acute heat tolerances are relatively high, even exposure to moderate (temperature span assessed ca. 3–29°C) acclimation temperatures for a 24 h period have strong negative effects on heat tolerance for four of the five species. Similarly, exposure time negatively affected heat tolerance, but depending on species and temperature.Together our results suggest that exposure to even moderately elevated temperatures for periods of 24 h or even shorter can lead to lower acute heat tolerance for cold adapted terrestrial arthropod species from sub‐Arctic and Arctic regions. Consequently, climate change leading to extended periods of mildly elevated temperatures may have strong negative effects on these species. We argue that this aspect is currently overlooked when assessing the ability of arthropods from Arctic and sub‐Artic regions to cope with climate changes as such predictions are typically based on acute heat tolerance estimates and with the assumption of beneficial acclimation responses. Read the free Plain Language Summary for this article on the Journal blog. [ABSTRACT FROM AUTHOR]

Under climate change, ectotherms will likely face pressure to adapt to novel thermal environments by increasing their upper thermal tolerance and its plasticity, a measure of thermal acclimation. Ectotherm populations with high thermal tolerance are often less thermally plastic, a trade‐off hypothesized to result from (i) a phenotypic limit on thermal tolerance above which plasticity cannot further increase the trait, (ii) negative genetic correlation or (iii) fitness trade‐offs between the two traits. Whether each hypothesis causes negative associations between thermal tolerance and plasticity has implications for the evolution of each trait.We empirically tested the limit and trade‐off hypotheses by leveraging the experimental tractability and thermal biology of the intertidal copepod Tigriopus californicus. Using populations from four latitudinally distributed sites in coastal California, six lines per population were reared under a laboratory common garden for two generations. Ninety‐six full sibling replicates (n = 4–5 per line) from a third generation were developmentally conditioned to 21.5 and 16.5°C until adulthood. We then measured the upper thermal tolerance and fecundity of sibships at each temperature.We detected a significant trade‐off in fecundity, a fitness corollary, between baseline thermal tolerance and its plasticity. Tigriopus californicus populations and genotypes with higher thermal tolerance were less thermally plastic. We detected negative directional selection on thermal plasticity under ambient temperature evidenced by reduced fecundity. These fitness costs of plasticity were significantly higher among thermally tolerant genotypes, consistent with the trade‐off hypothesis. This trade‐off was evident under ambient conditions, but not high temperature.Observed thermal plasticity and fecundity were best explained by a model incorporating both the limit and trade‐off hypotheses rather than models with parameters associated with one hypothesis. Effects of population and family on tolerance and plasticity negatively covaried, suggesting that a negative genetic correlation could not be ruled as contributing to negative associations between the traits. Our study provides a novel empirical test of the fitness trade‐off hypothesis that leverages a strong inference approach. We discuss our results' insights into how thermal adaptation may be constrained by physiological limits, genetic correlations, and fitness trade‐offs between thermal tolerance and its plasticity. Read the free Plain Language Summary for this article on the Journal blog. [ABSTRACT FROM AUTHOR]

This study reveals a new acclimation mechanism of the eukaryotic unicellular green alga Chlorella vulgaris in terms of the effect of varying atmospheric pressures on the structure and function of its photosynthetic apparatus using fluorescence induction measurements (JIP-test). The results indicate that low (400 mbar) and extreme low (<10 mbar) atmospheric pressure decreases the density and thus increases the fluidity of the thylakoid membrane, possibly facilitating plastoquinone (PQ) movement within the membrane and resulting in enhanced photosynthetic electron flow and photochemical quenching. Molecular dynamic simulations of different light harvesting complexes within thylakoid membrane models confirm this mechanism and reveal the associated atomic scale details. The exposure of microalga to an extremely low pressure (<10 mbar) in a 100% CO2 atmosphere (simulating the Mars atmosphere), reveals that the impact of extremely low atmospheric pressure on PQ mobility within the photosynthetic membrane, coupled with the low density of an almost 100% CO2 Mars-like atmosphere, results to a similar photosynthetic efficiency to that on Earth. These findings pave the way for the identification of novel functional acclimation mechanisms of microalgae to extreme environments that are vastly distinct from those found on Earth. This study reveals a new acclimation mechanism of microalgae in low atmospheric pressure. Experimental results and molecular dynamic simulations indicate that low atmospheric pressure reduces the density and enhances the fluidity of photosynthetic thylakoid membranes, leading to enhanced photochemical quenching. Particularly, extremely low pressure (<10 mbar) in a 100% CO2 atmosphere (Mars-like atmosphere) yields a photosynthetic efficiency comparable to that of Earth, shedding light on new astrobiological perspectives. [ABSTRACT FROM AUTHOR]

Up-flow sand filtration is an excellent alternative to point-of-use treatment for rural water supply. However, the sites and interval of microorganism growth in filter beds and the effect on bioclogging remain unknown. This study aimed to assess microorganism growth based on biological activity levels using Dissolved Oxygen (DO) consumption and Field Emission Scanning Electron Microscopy (FE-SEM) imaging in various zones of the filter bed. Additionally, pressure drop was monitored to evaluate bio-clogging. The results showed that microorganism activities differed within the 0.50 m up-flow sand filter bed during 8 weeks of acclimatization. Exponential growth started after day 35, and DO levels declined to a minimum of 2 mg/L at 0.10 m bed height (measured from the bottom) after day 46. At 0.30 m and 0.50 m height, the DO decreased to 0.8 mg/L and 0.3 mg/L after days 35 and 46, respectively. FE-SEM images confirmed microorganism growth on samples from 0.1 m after 4 weeks of acclimatization. Substantial growth was seen on samples of 0.10 and 0.30 m height at 8 weeks, while lesser growth was observed on samples of 0.50 m. The pressure drop showed no significant increase, signifying that clogging did not occur during the 135-day operational period. In conclusion, the up-flow configuration prevented bio-clogging in sand filters, reducing maintenance requirements. [ABSTRACT FROM AUTHOR]

Diatoms often outnumber other eukaryotic algae in the oceans, especially in coastal environments characterized by frequent fluctuations in light intensity. The identities and operational mechanisms of regulatory factors governing diatom acclimation to high light stress remain largely elusive. Here, we identified the AUREO1c protein from the coastal diatom Phaeodactylum tricornutum as a crucial regulator of non-photochemical quenching (NPQ), a photoprotective mechanism that dissipates excess energy as heat. AUREO1c detects light stress using a light-oxygen-voltage (LOV) domain and directly activates the expression of target genes, including LI818 genes that encode NPQ effector proteins, via its bZIP DNA-binding domain. In comparison to a kinase-mediated pathway reported in the freshwater green alga Chlamydomonas reinhardtii, the AUREO1c pathway exhibits a faster response and enables accumulation of LI818 transcript and protein levels to comparable degrees between continuous high-light and fluctuating-light treatments. We propose that the AUREO1c-LI818 pathway contributes to the resilience of diatoms under dynamic light conditions. Diatoms thrive in dynamic environments that frequently confer high light stress. In this study, the authors report a diatom photoreceptor that triggers immediate transcription of photoprotective genes upon high light signals. The fast response kinetics of this pathway confer advantages in environments with rapid light fluctuations. [ABSTRACT FROM AUTHOR]

Rising CO2, global warming, and N deposition create challenging environmental conditions to vegetation. Since elevated CO2 and rising temperature are coupled with each other, it is important to understand their combined effects on plants. We investigated the growth and photosynthetic responses of yellow birch to five levels of nitrogen supply under the current (cCT: current CO2 and temperature) and the predicted future CO2 and temperature conditions (fCT: elevated CO2, current + 4℃ temperature). The results show that fCT and high N supply increased seedling growth but fCT reduced photosynthetic capacity (e.g., maximum rate of Rubisco carboxylation-Vcmax, maximum rate of photosynthetic electron transport-Jmax)) and foliar N concentration. However, the magnitude of the fCT effect declined with increases in N supply. Furthermore, the fCT treatment significantly reduced the Jmax/Vcmax ratio, indicating a possible shift of N allocation from Jmax to Vcmax in the photosynthetic machinery. This result suggests that the photosynthesis of yellow birch may be more limited by electron transport under the predicted future climate condition. Both low N supply and fCT significantly increased photosynthetic N use efficiency (PNUE) and there was a negative relationship between PNUE and photosynthetic capacity. In general, yellow birch grew better under fCT than cCT, particularly above-ground growth. [ABSTRACT FROM AUTHOR]

Heat stroke (HS) is a critical condition with extremely high mortality. Heat acclimation (HA) is widely recognized as the best measure to prevent and protect against HS. Preventive administration of oral rehydration salts III (ORSIII) and probiotics have been reported to sustain intestinal function in cases of HS. This study established a rat model of HA that was treated with probiotics-based ORS (ORSP) during consecutive 21-day HA training. The results showed that HA with ORSP could attenuate HS-induced hyperthermia by regulating thermoregulatory response. We also found that HA with ORSP could significantly alleviate HSinduced multiple organ injuries. The expression levels of a series of heat-shock proteins (HSPs), including HSP90, HSP70, HSP60, and HSP40, were significantly up-regulated from the HA training. The increases in intestinal fatty acid binding protein (I-FABP) and D-Lactate typically seen during HS were decreased through HA. The representative TJ proteins including ZO-1, E-cadherin, and JAM-1 were found to be significantly down-regulated by HS, but sustained following HA. The ultrastructure of TJ was examined by TEM, which confirmed its protective effect on the intestinal barrier protection following HA. We also demonstrated that HA raised the intestinal levels of beneficial bacteria Lactobacillus and lowered those of the harmful bacteria Streptococcus through 16S rRNA gene sequencing. These findings suggest that HA with ORSP was proven to improve intestinal thermotolerance and the levels of protective gut microbiota against HS. [ABSTRACT FROM AUTHOR]

Up-flow sand filtration is an excellent alternative to point-of-use treatment for rural water supply. However, the sites and interval of microorganism growth in filter beds and the effect on bio-clogging remain unknown. This study aimed to assess microorganism growth based on biological activity levels using Dissolved Oxygen (DO) consumption and Field Emission Scanning Electron Microscopy (FE-SEM) imaging in various zones of the filter bed. Additionally, pressure drop was monitored to evaluate bio-clogging. The results showed that microorganism activities differed within the 0.50 m up-flow sand filter bed during 8 weeks of acclimatization. Exponential growth started after day 35, and DO levels declined to a minimum of 2 mg/L at 0.10 m bed height (measured from the bottom) after day 46. At 0.30 m and 0.50 m height, the DO decreased to 0.8 mg/L and 0.3 mg/L after days 35 and 46, respectively. FE-SEM images confirmed microorganism growth on samples from 0.1 m after 4 weeks of acclimatization. Substantial growth was seen on samples of 0.10 and 0.30 m height at 8 weeks, while lesser growth was observed on samples of 0.50 m. The pressure drop showed no significant increase, signifying that clogging did not occur during the 135-day operational period. In conclusion, the up-flow configuration prevented bio-clogging in sand filters, reducing maintenance requirements.

Abstract High altitude (HA) ascent imposes systemic hypoxia and associated risk of acute mountain sickness. Acute hypoxia elicits a hypoxic ventilatory response (HVR), which is augmented with chronic HA exposure (i.e., ventilatory acclimatization; VA). However, laboratory‐based HVR tests lack portability and feasibility in field studies. As an alternative, we aimed to characterize area under the curve (AUC) calculations on Fenn diagrams, modified by plotting portable measurements of end‐tidal carbon dioxide (PETCO2) against peripheral oxygen saturation (SpO2) to characterize and quantify VA during incremental ascent to HA (n = 46). Secondarily, these participants were compared with a separate group following the identical ascent profile whilst self‐administering a prophylactic oral dose of acetazolamide (Az; 125 mg BID; n = 20) during ascent. First, morning PETCO2 and SpO2 measurements were collected on 46 acetazolamide‐free (NAz) lowland participants during an incremental ascent over 10 days to 5160 m in the Nepal Himalaya. AUC was calculated from individually constructed Fenn diagrams, with a trichotomized split on ranked values characterizing the smallest, medium, and largest magnitudes of AUC, representing high (n = 15), moderate (n = 16), and low (n = 15) degrees of acclimatization. After characterizing the range of response magnitudes, we further demonstrated that AUC magnitudes were significantly smaller in the Az group compared to the NAz group (P = 0.0021), suggesting improved VA. These results suggest that calculating AUC on modified Fenn diagrams has utility in assessing VA in large groups of trekkers during incremental ascent to HA, due to the associated portability and congruency with known physiology, although this novel analytical method requires further validation in controlled experiments. Highlights What is the central question of this study? What are the characteristics of a novel methodological approach to assess ventilatory acclimatization (VA) with incremental ascent to high altitude (HA)? What is the main finding and its importance? Area under the curve (AUC) magnitudes calculated from modified Fenn diagrams were significantly smaller in trekkers taking an oral prophylactic dose of acetazolamide compared to an acetazolamide‐free group, suggesting improved VA. During incremental HA ascent, quantifying AUC using modified Fenn diagrams is feasible to assess VA in large groups of trekkers with ascent, although this novel analytical method requires further validation in controlled experiments.

Background: Altitude training is often regarded as an indispensable tool for the success of elite endurance athletes. Historically, altitude training emerged as a key strategy to prepare for the 1968 Olympics, held at 2300 m in Mexico City, and was limited to the "Live High-Train High" method for endurance athletes aiming for performance gains through improved oxygen transport. This "classical" intervention was modified in 1997 by the "Live High-Train Low" (LHTL) model wherein athletes supplemented acclimatization to chronic hypoxia with high-intensity training at low altitude. Purpose: This review discusses important considerations for successful implementation of LHTL camps in elite athletes based on experiences, both published and unpublished, of the authors. Approach: The originality of our approach is to discuss 10 key "lessons learned," since the seminal work by Levine and Stray-Gundersen was published in 1997, and focusing on (1) optimal dose, (2) individual responses, (3) iron status, (4) training-load monitoring, (5) wellness and well-being monitoring, (6) timing of the intervention, (7) use of natural versus simulated hypoxia, (8) robustness of adaptative mechanisms versus performance benefits, (9) application for a broad range of athletes, and (10) combination of methods. Successful LHTL strategies implemented by Team USA athletes for podium performance at Olympic Games and/or World Championships are presented. Conclusions: The evolution of the LHTL model represents an essential framework for sport science, in which field-driven questions about performance led to critical scientific investigation and subsequent practical implementation of a unique approach to altitude training. [ABSTRACT FROM AUTHOR]

The innate immune system is the body's first line of defense against infection. Natural killer (NK) cells, a vital part of the innate immune system, help to control infection and eliminate cancer. Studies have identified a vast array of receptors that NK cells use to discriminate between healthy and unhealthy cells. However, at present, it is difficult to explain how NK cells will respond to novel stimuli in different environments. In addition, the expression of different receptors on individual NK cells is highly stochastic, but the reason for these variegated expression patterns is unclear. Here, we studied the recognition of unhealthy target cells as an inference problem, where NK cells must distinguish between healthy targets with normal variability in ligand expression and ones that are clear "outliers." Our mathematical model fits well with experimental data, including NK cells' adaptation to changing environments and responses to different target cells. Furthermore, we find that stochastic, "sparse" receptor expression profiles are best able to detect a variety of possible threats, in agreement with experimental studies of the NK cell repertoire. While our study was specifically motivated by NK cells, our model is general and could also apply more broadly to explain principles of target recognition for other immune cell types.

Climate change has exacerbated the effects of abiotic stresses on plant growth and productivity. Drought is one of the most important abiotic stress factors that interfere with plant growth and development. Plant selection and breeding as well as genetic engineering methods used to improve crop drought tolerance are expensive and time consuming. Plants use a myriad of adaptative mechanisms to cope with the adverse effects of drought stress including the association with beneficial microorganisms such as plant growth promoting rhizobacteria (PGPR). Inoculation of plant roots with different PGPR species has been shown to promote drought tolerance through a variety of interconnected physiological, biochemical, molecular, nutritional, metabolic, and cellular processes, which include enhanced plant growth, root elongation, phytohormone production or inhibition, and production of volatile organic compounds. Therefore, plant colonization by PGPR is an eco-friendly agricultural method to improve plant growth and productivity. Notably, the processes regulated and enhanced by PGPR can promote plant growth as well as enhance drought tolerance. This review addresses the current knowledge on how drought stress affects plant growth and development and describes how PGPR can trigger plant drought stress responses at the physiological, morphological, and molecular levels.

Tooth classes are an innovation that has contributed to the evolutionary success of mammals. However, our understanding of the mechanisms by which tooth classes diversified remain limited. We use the evolutionary radiation of noctilionoid bats to show how the tooth developmental program evolved during the adaptation to new diet types. Combining morphological, developmental and mathematical modeling approaches, we demonstrate that tooth classes develop through independent developmental cascades that deviate from classical models. We show that the diversification of tooth number and size is driven by jaw growth rate modulation, explaining the rapid gain/loss of teeth in this clade. Finally, we mathematically model the successive appearance of tooth buds, supporting the hypothesis that growth acts as a key driver of the evolution of tooth number and size. Our work reveal how growth, by tinkering with reaction/diffusion processes, drives the diversification of tooth classes and other repeated structure during adaptive radiations.

Climate change drives species distribution shifts, affecting the availability of resources people rely upon for food and livelihoods. These impacts are complex, manifest at local scales, and have diverse effects across multiple species. However, for wild capture fisheries, current understanding is dominated by predictions for individual species at coarse spatial scales. We show that species-specific responses to localized environmental changes will alter the collection of co-occurring species within established fishing footprints along the U.S. West Coast. We demonstrate that availability of the most economically valuable, primary target species is highly likely to decline coastwide in response to warming and reduced oxygen concentrations, while availability of the most abundant, secondary target species will potentially increase. A spatial reshuffling of primary and secondary target species suggests regionally heterogeneous opportunities for fishers to adapt by changing where or what they fish. Developing foresight into the collective responses of species at local scales will enable more effective and tangible adaptation pathways for fishing communities.

Background: The effects of heat acclimation (HA) on the hypothalamus after exertional heatstroke (EHS) and the specific mechanism have not been fully elucidated, and this study aimed to address these questions. Methods: In the present study, rats were randomly assigned to the control, EHS, HA, or HA + EHS groups (n = 9). Hematoxylin and eosin (H&E) staining was used to examine pathology. Tandem mass tag (TMT)-based proteomic analysis was utilized to explore the impact of HA on the protein expression profile of the hypothalamus after EHS. Bioinformatics analysis was used to predict the functions of the differentially expressed proteins. The differential proteins were validated by western blotting. An enzyme-linked immunosorbent assay was used to measure the expression levels of inflammatory cytokines in the serum. Results: The H&E staining (n = 5) results revealed that there were less structural changes in hypothalamus in the HA + EHS group compared with the EHS group. Proteomic analysis (n = 4) revealed that proinflammatory proteins such as argininosuccinate synthetase (ASS1), high mobility group protein B2 (HMGB2) and vimentin were evidently downregulated in the HA + EHS group. The levels of interleukin (IL)-1β, IL-1, and IL-8 were decreased in the serum samples (n = 3) from HA + EHS rats. Conclusions: HA may alleviate hypothalamic damage caused by heat attack by inhibiting inflammatory activities, and ASS1, HMGB2 and vimentin could be candidate factors involved in the exact mechanism. [ABSTRACT FROM AUTHOR]

Summary: Heat stress transcription factors (HSFs) are the core regulators of the heat stress (HS) response in plants. HSFs are considered as a molecular rheostat: their activities define the response intensity, incorporating information about the environmental temperature through a network of partner proteins. A prompted activation of HSFs is required for survival, for example the de novo synthesis of heat shock proteins. Furthermore, a timely attenuation of the stress response is necessary for the restoration of cellular functions and recovery from stress. In an ever‐changing environment, the balance between thermotolerance and developmental processes such as reproductive fitness highlights the importance of a tightly tuned response. In many cases, the response is described as an ON/OFF mode, while in reality, it is very dynamic. This review compiles recent findings to update existing models about the HSF‐regulated HS response and address two timely questions: How do plants adjust the intensity of cellular HS response corresponding to the temperature they experience? How does this adjustment contribute to the fine‐tuning of the HS and developmental networks? Understanding these processes is crucial not only for enhancing our basic understanding of plant biology but also for developing strategies to improve crop resilience and productivity under stressful conditions. [ABSTRACT FROM AUTHOR]

Supplemental oxygen (hyperoxia) improves physical performance during hypoxic exercise. Based on the analysis of metabolome and iron homeostasis from human athlete blood samples, we show that hyperoxia during recovery periods interferes with metabolic alterations following hypoxic exercise. This may impair beneficial adaptations to exercise and/or hypoxia and highlights risks of oxygen supplementation in hypoxia. [Display omitted] • Hyperoxic recovery does not improve training efficiency of hypoxic exercise in healthy men. • Hyperoxic recovery prevents inter-session improvements of hypoxic exercise. • Hyperoxic recovery abolishes the metabolic fingerprint of hypoxic exercise after one week. • Hyperoxic recovery during hypoxic exercise may reduce hypoxia acclimatization, potentially increasing the risks of hypoxia. [ABSTRACT FROM AUTHOR]

Humic acid (HA) is a typical refractory organic matter, so it is of great significance to investigate its effect on the performance of Anammox granular sludge. When the dosage of HA ≤ 50 mg/L, HA promotes the total nitrogen removal rate (NRR) to 1.45 kg/(m3·day). When HA was between 50 and 100 mg/L, the NRR of Anammox was stable. At this time, the adsorption of HA causes the sludge to gradually turn from red to brown, but the activities of heme and enzymes showed that its capacity was not affected. When HA levels reached 250 mg/L, the NRR dropped to 0.11 kg/(m3·day). Moderate HA levels promoted the release of extracellular polymeric substance (EPS), but excessive HA levels lead to a decrease in EPS concentrations. HA inhibited Anammox activity, which indirectly hindered the transmission of substrate and accumulated substrate toxicity. Although HA promoted the increase of heterotrophic microbial abundance in Anammox system, the microbial diversity decreased gradually. With the increase of HA concentration, the abundance of Candidatus_Brocadia , the main functional microorganism of Anammox system, decreased gradually, while the abundance of Candidatus_Kuenenia increased gradually. [ABSTRACT FROM AUTHOR]

Due to the effects of low-pressure and hypoxic environments at high altitudes, drivers in high-altitude areas exhibit increased perceived reaction times, leading to challenges in accurate speed estimation and handling judgment. This study aims to quantitatively analyze the impact of plateau environments on operating speeds at interchange exit ramps. Utilizing a UC/win-road simulator, six scenarios of expressway exit ramps were constructed. The simulation experiments involved 50 participants (35 males, 15 females) from Nanjing, China (altitude of 50 m) and 50 participants (36 males, 14 females) from Lhasa, China (altitude of 3,650 m). This research focused on examining the influence of the plateau environment on drivers' operating speeds, investigating variations in speed between drivers in plain and plateau areas, across genders, and during different acclimation periods. It also aimed to predict operating speeds at the midpoint and exit of the curve on the exit ramp for drivers in both plain and plateau areas. Based on these predictions, the study elucidated the trend of operating speed as influenced by the low-pressure and hypoxic conditions of the plateau, as well as the characteristics of the exit ramp's horizontal curve. Additionally, the research uncovered the internal correlations and potential reasons linking operating speed to drivers' perception and response abilities, physiological and visual load levels, and driving styles. [ABSTRACT FROM AUTHOR]

Purpose: Although recommendations for effective heat acclimation (HA) strategies for many circumstances exist, best-practice HA protocols specific to elite female team-sport athletes are yet to be established. Therefore, the authors aimed to investigate the effectiveness and retention of a passive HA protocol integrated in a female Olympic rugby sevens team training program. Methods: Twelve elite female rugby sevens athletes undertook 10 days of passive HA across 2 training weeks. Tympanic temperature (TTymp), sweat loss, heart rate, and repeated 6-second cycling sprint performance were assessed using a sport-specific heat stress test Pre-HA, after 3 days (Mid-HA), after 10 days (Post-HA), and 15 days post-HA (Decay). Results: Compared with Pre-HA, submaximal TTymp was lower Mid-HA and Post-HA (both by −0.2 [0.7] °C; d ≥ 0.71), while resting TTymp was lower Post-HA (by −0.3 [0.2] °C; d = 0.81). There were no differences in TTymp at Decay compared with Pre-HA, nor were there any differences in heart rate or sweat loss at any time points. Mean peak 6-second power output improved Mid-HA and Post-HA (76 [36] W; 75 [34] W, respectively; d ≥ 0.45) compared with Pre-HA. The observed performance improvement persisted at Decay by 65 (45) W (d = 0.41). Conclusions: Ten days of passive HA can elicit some thermoregulatory and performance benefits when integrated into a training program in elite female team-sport athletes. However, such a protocol does not provide a sufficient thermal impulse for thermoregulatory adaptations to be retained after 15 days with no further heat stimulus. [ABSTRACT FROM AUTHOR]

Objective To investigate the effect of lifestyle on high-altitude de-adaptation (HADA) through questionnaire during the whole process of entering and existing the plateau in order to provide scientific basis for prevention and treatment of the disease. Methods A case-control trial was conducted on 1 751 participants from a certain unit who entered and existed the plateau together during 2021 and 2022. In 1 to 2 weeks after they returning from the plateau, they were surveyed, and finally, 1 544 valid questionnaires were obtained. According to the score of the plateau deacclimation scale ≥6 or not, the subjects were divided into plateau deacclimation group (n=192) and control group (n=1 352). They were further surveyed for their lifestyles and general conditions. Rank sum test was used to analyze the differences of lifestyles between the 2 groups, and unconditional logistic regression analysis was employed to identify the independent risk factors of HADA. Results Hair loss (19.95%), drowsiness (16.58%) and tiredness (12.31%) were the most common symptoms of HADA. High salt diet before entering the plateau, smoking at the plateau, altitude sickness (OR=1.893, 95%CI: 1.142~3.137, P=0.013), leaving the plateau by plane (OR=1.688, 95%CI: 1.082~2.634, P=0.021), and drinking much tea, excessive exercise intensity and insufficient sleep after leaving the plateau were independent risk factors for HADA. Conclusion Low salt diet before entering the plateau, active prevention for altitude sickness, smoking cessation at the plateau, taking a slower means of transportation to enter and leave the plateau, drinking less tea, moderate exercise intensity and keeping enough sleep after leaving the plateau can effectively reduce the risk of HADA.

Abstract The human spleen contracts in response to stress‐induced catecholamine secretion, resulting in a temporary rise in haemoglobin concentration ([Hb]). Recent findings highlighted enhanced splenic response to exercise at high altitude in Sherpa, possibly due to a blunted splenic response to hypoxia. To explore the potential blunted splenic contraction in Sherpas at high altitude, we examined changes in spleen volume during hyperoxic breathing, comparing acclimatized Sherpa with acclimatized individuals of lowland ancestry. Our study included 14 non‐Sherpa (7 female) residing at altitude for a mean continuous duration of 3 months and 46 Sherpa (24 female) with an average of 4 years altitude exposure. Participants underwent a hyperoxic breathing test at altitude (4300 m; barrometric pressure = ∼430 torr; PO2 = ∼90 torr). Throughout the test, we measured spleen volume using ultrasonography and monitored oxygen saturation (SpO2). During rest, Sherpa exhibited larger spleens (226 ± 70 mL) compared to non‐Sherpa (165 ± 34 mL; P

Objective To investigate the protective effects and underlying mechanisms of sodium butyrate on rats exposed to hypoxia and cold conditions. Methods Fifty-eight male SD rats (aged 7~8 weeks, weighing 240~260 g) were randomly divided into normoxia normothermia saline control (NNC) group (n=10), normoxia normothermia sodium butyrate (NNB) group (n=10), hypoxia cold saline control (HCC) group (n=19), and hypoxia cold sodium butyrate (HCB) group (n=19).The intragastric dose of sodium butyrate was 200 mg/kg for the NNB and HCB groups, while the NNC and HCC groups were given normal saline of 5 mL/kg.①After continuous intragastric administration for 7 d, the rats in the HCC and HCB groups were placed in a low-pressure hypoxic chamber to simulate an altitude of 5 000 m and exposed to a temperature of 8℃ for 7 d.Subsequently, blood samples were collected from the abdominal aorta for blood gas analysis, blood routine test, and detection for serum biochemical indicators.ELISA was used to determine serum inflammatory cytokines and endocrine hormones.The rats in the NNC and NNB groups (n=10) were fed outside the chamber and underwent the same tests in 7 d later to evaluate the protective effects of sodium butyrate on the body.②Core body temperature monitoring was conducted to assess the impact of sodium butyrate on thermoregulation in rats exposed to hypoxia and cold (n=3).③Hypoxia exercise tolerance of the HCC group and HCB group in a hypoxic chamber (11% O2) was evaluated for their hypoxia resistance (n=6). Results Compared to the NNC group, the rats in the HCC group exhibited significant decreases in arterial oxygen saturation (SaO2) and arterial oxygen partial pressure (PaO2), serum levels of IL-4, estradiol (E2) and cortisol (F), core temperature, and exercise duration (P < 0.05), and had notably increased levels of red blood cell (RBC) count, hemoglobin (HGB), hematocrit (HCT), cardiac troponin (CRDAC-T), uric acid (UA), alanine aminotransferase (ALT), total cholesterol (TC), low-density lipoprotein (LDL), IL-6 and granulocyte-macrophage colony-stimulating factor (GM-CSF)(P < 0.05).Compared to the HCC group, the rats in the HCB group exhibited significant increases in SaO2, PaO2, IL-4, E2, F, corticotropin releasing hormone (CRH) and adrenocorticotropic hormone (ACTH)(P < 0.05), remarkably longer exercise duration under hypoxic exposure (P < 0.05), but decreases in RBC count, serum levels of HGB, HCT, CRDAC-T, UA, ALT, TC, LDL, IL-6, GM-CSF and free thyroxine (FT4), and core temperature (P < 0.05). Conclusion Sodium butyrate exhibits protective effects on rats exposed to hypoxia and cold conditions, and it is helpful in their adaptation to these hypoxia and cold environments.

Abstract Local adaptation can increase fitness under stable environmental conditions. However, in rapidly changing environments, compensatory mechanisms enabled through plasticity may better promote fitness. Climate change is causing devastating impacts on coral reefs globally and understanding the potential for adaptive and plastic responses is critical for reef management. We conducted a four-year, three-way reciprocal transplant of the Caribbean coral Siderastrea siderea across forereef, backreef, and nearshore populations in Belize to investigate the potential for environmental specialization versus plasticity in this species. Corals maintained high survival within forereef and backreef environments, but transplantation to nearshore environments resulted in high mortality, suggesting that nearshore environments present strong environmental selection. Only forereef-sourced corals demonstrated evidence of environmental specialization, exhibiting the highest growth in the forereef. Gene expression profiling 3.5 years post-transplantation revealed that transplanted coral hosts exhibited profiles more similar to other corals in the same reef environment, regardless of their source location, suggesting that transcriptome plasticity facilitates acclimatization to environmental change in S. siderea. In contrast, algal symbiont (Cladocopium goreaui) gene expression showcased functional variation between source locations that was maintained post-transplantation. Our findings suggest limited acclimatory capacity of some S. siderea populations under strong environmental selection and highlight the potential limits of coral physiological plasticity in reef restoration.

Aquatic ferns of the genus Azolla (Azolla) form highly productive symbioses with filamentous cyanobacteria fixing N2 in their leaf cavities, Nostoc azollae. Stressed symbioses characteristically turn red due to 3‐deoxyanthocyanidin (DA) accumulation, rare in angiosperms and of unknown function. To understand DA accumulation upon cold acclimation and recovery, we integrated laser‐desorption‐ionization mass‐spectrometry‐imaging (LDI‐MSI), a new Azolla filiculoides genome‐assembly and annotation, and dual RNA‐sequencing into phenotypic analyses of the symbioses. Azolla sp. Anzali recovered even when cold‐induced DA‐accumulation was inhibited by abscisic acid. Cyanobacterial filaments generally disappeared upon cold acclimation and Nostoc azollae transcript profiles were unlike those of resting stages formed in cold‐resistant sporocarps, yet filaments re‐appeared in leaf cavities of newly formed green fronds upon cold‐recovery. The high transcript accumulation upon cold acclimation of AfDFR1 encoding a flavanone 4‐reductase active in vitro suggested that the enzyme of the first step in the DA‐pathway may regulate accumulation of DAs in different tissues. However, LDI‐MSI highlighted the necessity to describe metabolite accumulation beyond class assignments as individual DA and caffeoylquinic acid metabolites accumulated differentially. For example, luteolinidin accumulated in epithelial cells, including those lining the leaf cavity, supporting a role for the former in the symbiotic interaction during cold acclimation. [ABSTRACT FROM AUTHOR]

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]

Background: Light deficit in shaded environment critically impacts the growth and development of turf plants. Despite this fact, past research has predominantly concentrated on shade avoidance rather than shade tolerance. To address this, our study examined the photosynthetic adjustments of Bermudagrass when exposed to varying intensities of shade to gain an integrative understanding of the shade response of C4 turfgrass. Results: We observed alterations in photosynthetic pigment-proteins, electron transport and its associated carbon and nitrogen assimilation, along with ROS-scavenging enzyme activity in shaded conditions. Mild shade enriched Chl b and LHC transcripts, while severe shade promoted Chl a, carotenoids and photosynthetic electron transfer beyond QA− (ET0/RC, φE0, Ψ0). The study also highlighted differential effects of shade on leaf and root components. For example, Soluble sugar content varied between leaves and roots as shade diminished SPS, SUT1 but upregulated BAM. Furthermore, we observed that shading decreased the transcriptional level of genes involving in nitrogen assimilation (e.g. NR) and SOD, POD, CAT enzyme activities in leaves, even though it increased in roots. Conclusions: As shade intensity increased, considerable changes were noted in light energy conversion and photosynthetic metabolism processes along the electron transport chain axis. Our study thus provides valuable theoretical groundwork for understanding how C4 grass acclimates to shade tolerance. [ABSTRACT FROM AUTHOR]

The Angoumois grain moth, Sitotroga cerealella (Olivier), is a significant cosmopolitan primary pest of cereals worldwide and has thrived in divergent environments. However, the mechanisms underlying its survival in multiple contrasting environments are poorly understood. Here, we hypothesised that when facing diverse environmental stress, F1 generation exhibits transgenerational cross‐protection as a mechanism to persist under divergent stressful environments. Notably, F1 acclimation to cold or desiccation conditions could either enhance or lower heat tolerance in the F2 generation. Specifically, we tested whether typical diurnal fluctuations and/or winter rapid or chronic cold temperatures (18–22°C) as well as desiccation acclimation of F1 parental population yields transgenerational cross‐protection/susceptibility to heat stress on F2 offspring. F1 moths were exposed to cold hardening (2 h), chronic (72 h) and variable (fluctuating between 18 and 22°C for 72 h) temperature treatment groups. Desiccation treatment included incubation at 0%–1% relative humidity (24 h). F2 generation moths were then assessed for heat tolerance using critical thermal maxima (CTmax) at three different ramping rates (0.06, 0.25 and 0.5°C/min) as well as heat knockdown time (HKDT). Findings indicated that (i) desiccation, cold hardening and chronic low‐temperature acclimations in F1 reduced heat tolerance in F2 populations and (ii) ramping rate was crucial to decipher differences between treatment groups, with lower ramping rates associated with lower CTmax. Transgenerational cross‐susceptibility to heat stress indicates possible fitness costs of exposure to multiple contrasting stressors in the Angoumois grain moth and can be used in designing physical pest management strategies. [ABSTRACT FROM AUTHOR]

Certain cyanobacteria alter their photosynthetic light absorption between green and red, a phenomenon called complementary chromatic acclimation. The acclimation is regulated by a cyanobacteriochrome-class photosensor that reversibly photoconverts between green-absorbing (Pg) and red-absorbing (Pr) states. Here, we elucidated the structural basis of the green/red photocycle. In the Pg state, the bilin chromophore adopted the extended C15-Z,anti structure within a hydrophobic pocket. Upon photoconversion to the Pr state, the bilin is isomerized to the cyclic C15-E,syn structure, forming a water channel in the pocket. The solvation/desolvation of the bilin causes changes in the protonation state and the stability of π-conjugation at the B ring, leading to a large absorption shift. These results advance our understanding of the enormous spectral diversity of the phytochrome superfamily. [ABSTRACT FROM AUTHOR]

Fish live in aquatic areas with varying salinity from fresh water to seawater. Gills are one of the most important osmoregulatory organs for maintaining the salt–water balance. In this study, changes in the gills of velifera (Poecilia sphenops) acclimated to 20, 30, 40, and 50 ppt of saline in the laboratory were examined histologically and immunohistochemically. Mucus cells (MCs), proliferating cell nuclear antigen (PCNA), mitochondria-rich cells (MRCs), and heat shock proteins (HSP70) + cells were marked in the gill tissue, which underwent routine histological procedures, and the severity of histological alterations increase with the increase of the salinity. When the gills were examined histologically, it was determined that there was an increase in cells due to hyperplasia, especially in the primary lamellae. A rapid increase in MC and HSP70 + cell numbers was observed in the 20 and 30 ppt groups. Although PCNA + cells were present in each salinity group, they were observed in the salinity group up to 50 ppt. An increase in the number and volume of MRCs was observed with increasing salinity. Based on the histological and immunohistochemical results, it is thought that the cytological and molecular arrangements of cells in gills of sailfin velifera under different levels of salinity are essential for the regulation of ion and salt balance. [ABSTRACT FROM AUTHOR]

To investigate how and to what extent there are differences in the photosynthetic plasticity of trees in response to different light environments, six species from three successional groups (late successional, mid‐successional, and pioneers) were exposed to three different light environments [deep shade – DS (5% full sunlight – FS), moderate shade – MS (35% FS) and full sunlight – FS].Maximum net photosynthesis (Amax), leaf N partitioning, stomatal, mesophile, and biochemical limitations (SL, ML, and BL, respectively), carboxylation velocity (Vcmax), and electron transport (Jmax) rates, and the state of photosynthetic induction (IS) were evaluated.Higher values of Amax, Vcmax, and Jmax in FS were observed for pioneer species, which invested the largest amount of leaf N in Rubisco. The lower IS for pioneer species reveals its reduced ability to take advantage of sunflecks. In general, the main photosynthetic limitations are diffusive, with SL and ML having equal importance under FS, and ML decreasing along with irradiance. The leaf traits, which are more determinant of the photosynthetic process, respond independently in relation to the successional group, especially with low light availability.An effective partitioning of leaf N between photosynthetic and structural components played a crucial role in the acclimation process and determined the increase or decrease of photosynthesis in response to the light conditions. [ABSTRACT FROM AUTHOR]

Knowledge of thermal tolerance limits provides important clues to the capacity of a species to withstand acute and chronic thermal changes. Climate models predict the increase and intensification of events such as heat waves, therefore understanding the upper thermal limits that a species can tolerate has become of utmost importance. We measured the upper thermal tolerance of the endemic Magdalena river stingray Potamotrygon magdalenae acclimated to experimental conditions, and then used critical thermal methodology to find the temperature at which an organism reaches a critical endpoint where locomotory activity becomes disorganized and the animal loses its ability to escape from conditions that will promptly lead to its death. We also describe the behavioral response of individuals to acute thermal stress and infer the possible consequences of temperature increases in the habitats of P. magdalenae populations. There were no significant differences between sexes in temperature tolerance or behavior. The critical thermal maximum (39°C) was 5.9°C above the maximum recorded temperature for the study area. Although P. magdalenae was tolerant to high temperature and currently is not living at its upper thermal limit, its survival in Guarinocito Pond will be threatened if temperatures continue to increase, considering the warming scenarios predicted for tropical regions due to climate change, even including short‐term climate phenomena such as El Niño. [ABSTRACT FROM AUTHOR]

Withania somnifera (Ashwagandha) is a valuable therapeutic plant used in many Ayurvedic drugs marketed for health restoration. However, its commercial production faces challenges due to poor seed viability, low germination rates, and the absence of standardized propagation methods. Therefore, this investigation aimed to establish a fast and highly efficient method for direct shoot regeneration in W. somnifera by using the apical meristem perforation technique, which is a novel approach. Initially, rapid seed germination was standardized by soaking the seeds in distilled water for varying durations (0 to 48 h). The highest rates of shoot initiation (90.40 ± 0.51%) and mean number of direct shoot regenerations (16.20 ± 0.50 per explant) were achieved on MS basal medium fortified with meta-topolin (mT) at 3.0 mg L−1. For optimal root development, shoots (3 to 4 cm) were cultured on half-strength Murashige and Skoog (MS) medium with 3.0 mg L−1 indole-3-butyric acid (IBA). Subsequently, well-rooted seedlings (90% survival rate) were acclimatized under glasshouse conditions in pots filled with a mixture of sandy loam and vermicompost (4:1). Anatomical examination of leaves and stems from micropropagated and acclimatized glasshouse plants revealed well-developed cuticles, differentiated mesophylls, and vascular bundles. Furthermore, the accumulations of withaferin A (1.26 ± 0.12 mg g−1), withanone (1.39 ± 0.18 mg g−1), and withanoside V (0.11 ± 0.04 mg g−1) in greenhouse-acclimated plant leaves were 1.88, 2.28, and 2.30 times higher, respectively, than in tissue culture samples (0.52 ± 0.07 mg g−1, 0.73 ± 0.02 mg g−1, and 0.05 ± 0.02 mg g−1). In conclusion, the described procedure offered an effective and straightforward method for large-scale production of W. somnifera plants for commercial metabolites. [ABSTRACT FROM AUTHOR]