Deciphering desiccation tolerance in wild eggplant species: insights from chlorophyll fluorescence dynamics.

BACKGROUND: Climate change exacerbates abiotic stresses, which are expected to intensify their impact on crop plants. Drought, the most prevalent abiotic stress, significantly affects agricultural production worldwide. Improving eggplant varieties to withstand abiotic stress is vital due to rising drought from climate change. Despite the diversity of wild eggplant species that thrive under harsh conditions, the understanding of their drought tolerance mechanisms remains limited. In the present study, we used chlorophyll fluorescence (ChlaF) imaging, which reveals a plant's photosynthetic health, to investigate desiccation tolerance in eggplant and its wild relatives. Conventional fluorescence measurements lack spatial heterogeneity, whereas ChlaF imaging offers comprehensive insights into plant responses to environmental stresses. Hence, employing noninvasive imaging techniques is essential for understanding this heterogeneity. RESULTS: Desiccation significantly reduced the leaf tissue moisture content (TMC) across species. ChlaF and TMC displayed greater photosystem II (PSII) efficiency after 54 h of desiccation in S. macrocarpum, S. torvum, and S. indicum, with S. macrocarpum demonstrating superior efficiency due to sustained fluorescence. PSII functions declined gradually in S. macrocarpum and S. torvum, unlike those in other species, which exhibited abrupt declines after 54 h of desiccation. However, after 54 h, PSII efficiency remained above 50% of its initial quantum yield in S. macrocarpum at 35% leaf RWC (relative water content), while S. torvum and S. indicum displayed 50% decreases at 31% and 33% RWC, respectively. Conversely, the susceptible species S. gilo and S. sisymbriifolium exhibited a 50% reduction in PSII function at an early stage of 50% RWC, whereas in S. melongena, this reduction occurred at 40% RWC. CONCLUSION: Overall, our study revealed notably greater leaf desiccation tolerance, especially in S. macrocarpum, S. torvum, and S. indicum, attributed to sustained PSII efficiency at low TMC levels, indicating that these species are promising sources of drought tolerance.

Physiological, transcriptomic and metabolomic insights of three extremophyte woody species living in the multi-stress environment of the Atacama Desert.

MAIN CONCLUSIONS: In contrast to Neltuma species, S. tamarugo exhibited higher stress tolerance, maintaining photosynthetic performance through enhanced gene expression and metabolites. Differentially accumulated metabolites include chlorophyll and carotenoids and accumulation of non-nitrogen osmoprotectants. Plant species have developed different adaptive strategies to live under extreme environmental conditions. Hypothetically, extremophyte species present a unique configuration of physiological functions that prioritize stress-tolerance mechanisms while carefully managing resource allocation for photosynthesis. This could be particularly challenging under a multi-stress environment, where the synthesis of multiple and sequential molecular mechanisms is induced. We explored this hypothesis in three phylogenetically related woody species co-occurring in the Atacama Desert, Strombocarpa tamarugo, Neltuma alba, and Neltuma chilensis, by analyzing their leaf dehydration and freezing tolerance and by characterizing their photosynthetic performance under natural growth conditions. Besides, the transcriptomic profiling, biochemical analyses of leaf pigments, and metabolite analysis by untargeted metabolomics were conducted to study gene expression and metabolomic landscape within this challenging multi-stress environment. S. tamarugo showed a higher photosynthetic capacity and leaf stress tolerance than the other species. In this species, a multifactorial response was observed, which involves high photochemical activity associated with a higher content of chlorophylls and ß-carotene. The oxidative damage of the photosynthetic apparatus is probably attenuated by the synthesis of complex antioxidant molecules in the three species, but S. tamarugo showed the highest antioxidant capacity. Comparative transcriptomic and metabolomic analyses among the species showed the differential expression of genes involved in the biosynthetic pathways of key stress-related metabolites. Moreover, the synthesis of non-nitrogen osmoprotectant molecules, such as ciceritol and mannitol in S. tamarugo, would allow the nitrogen allocation to support its high photosynthetic capacity without compromising leaf dehydration tolerance and freezing stress avoidance.

Is a seasonally reduced growth potential a convergent strategy to survive drought and frost in plants?

BACKGROUND: Plants have adapted to survive seasonal life-threatening frost and drought. However, the timing and frequency of such events are impacted by climate change, jeopardizing plant survival. Understanding better the strategies of survival to dehydration stress is therefore timely and can be enhanced by the cross-fertilization of research between disciplines (ecology, physiology), models (woody, herbaceous species) and types of stress (drought, frost). SCOPE: We build upon the 'growth-stress survival' trade-off, which underpins the identification of global plant strategies across environments along a 'fast-slow' economics spectrum. Although phenological adaptations such as dormancy are crucial to survive stress, plant global strategies along the fast-slow economic spectrum rarely integrate growth variations across seasons. We argue that the growth-stress survival trade-off can be a useful framework to identify convergent plant ecophysiological strategies to survive both frost and drought. We review evidence that reduced physiological activity, embolism resistance and dehydration tolerance of meristematic tissues are interdependent strategies that determine thresholds of mortality among plants under severe frost and drought. We show that complete dormancy, i.e. programmed growth cessation, before stress occurrence, minimizes water flows and maximizes dehydration tolerance during seasonal life-threatening stresses. We propose that incomplete dormancy, i.e. the programmed reduction of growth potential during the harshest seasons, could be an overlooked but major adaptation across plants. Quantifying stress survival in a range of non-dormant versus winter- or summer-dormant plants, should reveal to what extent incomplete to complete dormancy could represent a proxy for dehydration tolerance and stress survival. CONCLUSIONS: Our review of the strategies involved in dehydration stress survival suggests that winter and summer dormancy are insufficiently acknowledged as plant ecological strategies. Incorporating a seasonal fast-slow economics spectrum into global plant strategies improves our understanding of plant resilience to seasonal stress and refines our prevision of plant adaptation to extreme climatic events.

Expression dynamics of dehydration tolerance in the tropical plant Marchantia inflexa.

Tolerance to prolonged water deficit occurs along a continuum in plants, with dehydration tolerance (DhT) and desiccation tolerance (DT) representing some of the most extreme adaptations to water scarcity. Although DhT and DT presumably vary among individuals of a single species, this variability remains largely unstudied. Here, we characterized expression dynamics throughout a dehydration-rehydration time-course in six diverse genotypes of the dioecious liverwort Marchantia inflexa. We identified classical signatures of stress response in M. inflexa, including major changes in transcripts related to metabolism, expression of LEA and ELIP genes, and evidence of cell wall remodeling. However, we detected very little temporal synchronization of these responses across different genotypes of M. inflexa, which may be related to genotypic variation among samples, constitutive expression of dehydration-associated transcripts, the sequestration of mRNAs in ribonucleoprotein partials prior to drying, or the lower tolerance of M. inflexa relative to most bryophytes studied to date. Our characterization of intraspecific variation in expression dynamics suggests that differences in the timing of transcriptional adjustments contribute to variation among genotypes, and that developmental differences impact the relative tolerance of meristematic and differentiated tissues. This work highlights the complexity and variability of water stress tolerance, and underscores the need for comparative studies that seek to characterize variation in DT and DhT.

Insights from a vertebrate model organism on the molecular mechanisms of whole-body dehydration tolerance.

Studies on the molecular mechanisms of dehydration tolerance have been largely limited to plants and invertebrates. Currently, research in whole body dehydration of complex animals is limited to cognitive and behavioral effects in humans, leaving the molecular mechanisms of vertebrate dehydration relatively unexplored. The present review summarizes studies to date on the African clawed frog (Xenopus laevis) and examines whole-body dehydration on physiological, cellular and molecular levels. This aquatic frog is exposed to seasonal droughts in its native habitat and can endure a loss of over 30% of its total body water. When coping with dehydration, osmoregulatory processes prioritize water retention in skeletal tissues and vital organs over plasma volume. Although systemic blood circulation is maintained in the vital organs and even elevated in the brain during dehydration, it is done so at the expense of reduced circulation to the skeletal muscles. Increased hemoglobin affinity for oxygen helps to counteract impaired blood circulation and metabolic enzymes show altered kinetic and regulatory parameters that support the use of anaerobic glycolysis. Recent studies with X. laevis also show that pro-survival pathways such as antioxidant defenses and heat shock proteins are activated in an organ-specific manner during dehydration. These pathways are tightly coordinated at the post-transcriptional level by non-coding RNAs, and at the post-translational level by reversible protein phosphorylation. Paired with ongoing research on the X. laevis genome, the African clawed frog is poised to be an ideal animal model with which to investigate the molecular adaptations for dehydration tolerance much more deeply.

Evolutionary divergence of potential drought adaptations between two subspecies of an annual plant: Are trait combinations facilitated, independent, or constrained?

PREMISE: Whether drought-adaptation mechanisms tend to evolve together, evolve independently, or evolve constrained by genetic architecture is incompletely resolved, particularly for water-relations traits besides gas exchange. We addressed this issue in two subspecies of Clarkia xantiana (Onagraceae), California winter annuals that separated approximately 65,000 years ago and are adapted, partly by differences in flowering time, to native ranges differing in precipitation. METHODS: In these subspecies and in recombinant inbred lines (RILs) from a cross between them, we scored traits related to drought adaptation (timing of seed germination and of flowering, succulence, pressure-volume curve variables) in common environments. RESULTS: The subspecies native to more arid environments (parviflora) exhibited slower seed germination in saturated conditions, earlier flowering, and greater succulence, likely indicating superior drought avoidance, drought escape, and dehydration resistance via water storage. The other subspecies (xantiana) had lower osmotic potential at full turgor and lower water potential at turgor loss, implying superior dehydration tolerance. Genetic correlations among RILs suggest facilitated evolution of some trait combinations and independence of others. Where genetic correlations exist, subspecies differences fell along them, with the exception of differences in succulence and turgor loss point. In that case, subspecies difference overcame genetic correlations, possibly reflecting strong selection and/or antagonistic genetic correlations with other traits. CONCLUSIONS: Clarkia xantiana subspecies' differ in multiple mechanisms of drought adaptation. Genetic architecture generally does not seem to have constrained the evolution of these mechanisms, and it may have facilitated the evolution of some of trait combinations.

Adult diet does not compensate for impact of a poor larval diet on stress resistance in a tephritid fruit fly.

Adult holometabolous insects may derive metabolic resources from either larval or adult feeding, but little is known of whether adult diets can compensate for deficiencies in the larval diet in terms of stress resistance. We investigated how stress resistance is affected and compensated for by diet across life stages in the marula fruit fly Ceratitis cosyra (Diptera: Tephritidae). Larvae were fed diets containing either 8% torula yeast, the standard diet used to rear this species, or 1% yeast (low protein content similar to known host fruit). At emergence, adults from each larval diet were tested for initial mass, water content, body composition, and desiccation and starvation resistance or they were allocated to one of two adult diet treatments: sucrose only, or sucrose and yeast hydrolysate. The same assays were then repeated after 10 days of adult feeding. Development on a low protein larval diet led to lower body mass and improved desiccation and starvation resistance in newly emerged adults, even though adults from the high protein larval diet had the highest water content. Adult feeding decreased desiccation or starvation resistance, regardless of the diet provided. Irrespective of larval diet history, newly emerged, unfed adults had significantly higher dehydration tolerance than those that were fed. Lipid reserves played a role in starvation resistance. There was no evidence for metabolic water from stored nutrients extending desiccation resistance. Our findings show the possibility of a nutrient-poor larval environment leading to correlated improvement in adult performance, at least in the short term.

A RhABF2/Ferritin module affects rose (Rosa hybrida) petal dehydration tolerance and senescence by modulating iron levels.

Plants often develop the capacity to tolerate moderate and reversible environmental stresses, such as drought, and to re-establish normal development once the stress has been removed. An example of this phenomenon is provided by cut rose (Rosa hybrida) flowers, which experience typical reversible dehydration stresses during post-harvest handling after harvesting at the bud stages. The molecular mechanisms involved in rose flower dehydration tolerance are not known, however. Here, we characterized a dehydration- and abscisic acid (ABA)-induced ferritin gene (RhFer1). Dehydration-induced free ferrous iron (Fe2+ ) is preferentially sequestered by RhFer1 and not transported outside of the petal cells, to restrict oxidative stresses during dehydration. Free Fe2+ accumulation resulted in more serious oxidative stresses and the induction of genes encoding antioxidant enzyme in RhFer1-silenced petals, and poorer dehydration tolerance was observed compared with tobacco rattle virus (TRV) controls. We also determined that RhABF2, an AREB/ABF transcription factor involved in the ABA signaling pathway, can activate RhFer1 expression by directly binding to its promoter. The silencing of RhABF2 decreased dehydration tolerance and disrupted Fe homeostasis in rose petals during dehydration, as did the silencing of RhFer1. Although both RhFer1 and Fe transporter genes are induced during flower natural senescence in plants, the silencing of RhABF2 or RhFer1 accelerates the petal senescence processes. These results suggest that the regulatory module RhABF2/RhFer1 contributes to the maintenance of Fe levels and enhances dehydration tolerance through the action of RhFer1 locally sequestering free Fe2+ under dehydration conditions, and plays synergistic roles with transporter genes during flower senescence.

Anuran amphibians as comparative models for understanding extreme dehydration tolerance: a unique negative feedback lymphatic mechanism for blood volume regulation.

Anurans are the most terrestrial order of amphibians. Couple the high driving forces for evaporative loss in terrestrial environments and their low resistance to evaporation, dehydration is an inevitable stress on their water balance. Anurans have the greatest tolerances for dehydration of any vertebrate group. Some species can tolerate evaporative losses up to 45% of their standard body mass. Anurans have remarkable capacities to regulate blood volume with hemorrhage and dehydration compared with mammals. Stabilization of blood volume is central to extending dehydration tolerance, since it avoids both the hypovolemic and hyperviscosity stresses on cardiac output and its consequential effects on aerobic capacity. Anurans, in contrast to mammals, seem incapable of generating a sufficient pressure difference, either oncotically or via interstitial compliance, to move fluid from the interstitium into the capillaries. Couple this inability to generate a sufficient pressure difference for transvascular uptake to a circulatory system with high filtration coefficients and a high rate of plasma turnover is the consequence. The novel lymphatic system of anurans is critical to a remarkable capacity for blood volume regulation. This review summarizes what is known about the anatomical and physiological specializations that are involved in explaining differential blood volume regulation and dehydration tolerance involving a true centrally mediated negative feedback of lymphatic function involving baroreceptors as sensors and lymph hearts, arginine vasotocin, pulmonary ventilation and specialized skeletal muscles as effectors.

Avian thermoregulation in the heat: is evaporative cooling more economical in nocturnal birds?

Evaporative cooling is a prerequisite for avian occupancy of hot, arid environments, and is the only avenue of heat dissipation when air temperatures (Ta) exceed body temperature (Tb). Whereas diurnal birds can potentially rehydrate throughout the day, nocturnal species typically forgo drinking between sunrise and sunset. We hypothesized that nocturnal birds have evolved reduced rates of evaporative water loss (EWL) and more economical evaporative cooling mechanisms compared with diurnal species, permitting nocturnal species to tolerate extended periods of intense heat without becoming lethally dehydrated. We used phylogenetically informed regressions to compare EWL and evaporative cooling efficiency [ratio of evaporative heat loss (EHL) and metabolic heat production (MHP); EHL/MHP] among nocturnal and diurnal birds at high Ta We analyzed variation in three response variables: (1) slope of EWL at Ta between 40 and 46°C, (2) EWL at Ta=46°C and (3) EHL/MHP at Ta=46°C. Nocturnality emerged as a weak, negative predictor, with nocturnal species having slightly shallower slopes and reduced EWL compared with diurnal species of similar mass. In contrast, nocturnal activity was positively correlated with EHL/MHP, indicating a greater capacity for evaporative cooling in nocturnal birds. However, our analysis also revealed conspicuous differences among nocturnal taxa. Caprimulgids and Australian owlet-nightjars had shallower slopes and reduced EWL compared with similarly sized diurnal species, whereas owls had EWL rates comparable to those of diurnal species. Consequently, our results did not unequivocally demonstrate more economical cooling among nocturnal birds. Owls predominately select refugia with cooler microclimates, but the more frequent and intense heat waves forecast for the 21st century may increase microclimate temperatures and the necessity for active heat dissipation, potentially increasing owls' vulnerability to dehydration and hyperthermia.

Are winter and summer dormancy symmetrical seasonal adaptive strategies? The case of temperate herbaceous perennials.

BACKGROUND: Dormancy in higher plants is an adaptive response enabling plant survival during the harshest seasons and has been more explored in woody species than in herbaceous species. Nevertheless, winter and summer shoot meristem dormancy are adaptive strategies that could play a major role in enhancing seasonal stress tolerance and resilience of widespread herbaceous plant communities. SCOPE: This review outlines the symmetrical aspects of winter and summer dormancy in order to better understand plant adaptation to severe stress, and highlight research priorities in a changing climate. Seasonal dormancy is a good model to explore the growth-stress survival trade-off and unravel the relationships between growth potential and stress hardiness. Although photoperiod and temperature are known to play a crucial, though reversed, role in the induction and release of both types of dormancy, the thresholds and combined effects of these environmental factors remain to be identified. The biochemical compounds involved in induction or release in winter dormancy (abscisic acid, ethylene, sugars, cytokinins and gibberellins) could be a priority research focus for summer dormancy. To address these research priorities, herbaceous species, being more tractable than woody species, are excellent model plants for which both summer and winter dormancy have been clearly identified. CONCLUSIONS: Summer and winter dormancy, although responding to inverse conditions, share many characteristics. This analogous nature can facilitate research as well as lead to insight into plant adaptations to extreme conditions and the evolution of phenological patterns of species and communities under climate change. The development of phenotypes showing reduced winter and/or enhanced summer dormancy may be expected and could improve adaptation to less predictable environmental stresses correlated with future climates. To this end, it is suggested to explore the inter- and intraspecific genotypic variability of dormancy and its plasticity according to environmental conditions to contribute to predicting and mitigating global warming.

Physiological mechanisms of dehydration tolerance contribute to the invasion potential of Ceratitis capitata (Wiedemann) (Diptera: Tephritidae) relative to its less widely distributed congeners.

BACKGROUND: The Mediterranean fruit fly, Ceratitis capitata (Wiedemann) (Diptera: Tephritidae) is a highly invasive species now with an almost cosmopolitan distribution. Two other damaging, polyphagous and closely-related species, the marula fruit fly, Ceratitis cosyra (Walker), and the Natal fly, Ceratitis rosa Karsch, are not established outside of sub-Saharan Africa. In this study, adult water balance traits and nutritional body composition were measured in all three species at different temperatures and levels of relative humidity to determine whether tolerance of water stress may partially explain their distribution. RESULTS: Adult C. capitata exhibited higher desiccation resistance than C. rosa but not C. cosyra. Desiccation resistance of C. capitata was associated with lower rates of water loss under hot and dry conditions, higher dehydration tolerance, and higher lipid reserves that were catabolised during water stress. In comparison with C. capitata, C. cosyra and C. rosa lost water at significantly higher rates under hot, dry conditions, and did not catabolise lipids or other sources of metabolic water during water stress. CONCLUSIONS: These results suggest that adult physiological traits permitting higher tolerance of water stress play a role in the success of C. capitata, particularly relative to C. rosa. The distribution of C. cosyra is likely determined by the interaction of temperature with water stress, as well as the availability of suitable hosts for larval development.

Summer dormancy, drought survival and functional resource acquisition strategies in California perennial grasses.

BACKGROUND AND AIMS: Evidence suggests drought severity is increasing due to climate change, but strategies promoting severe drought survival in perennial grasses have been seldom explored. This is particularly true of summer dormancy, an adaptation common in summer-dry Mediterranean-type climates. In addition, though theory predicts superior drought survival results in lower potential productivity, studies rarely measure both drought survival and growth under optimal conditions. METHODS: Physiological and functional ecological approaches were integrated to quantify interspecific variation in foliar and root traits in a suite of eight California perennial grass species. In a glasshouse experiment, summer dormancy, foliar functional trait variation, and seasonal growth and phenology under non-limiting water conditions and dehydration tolerance under progressive drought were quantified. In a second glasshouse study, root functional traits were quantified under non-limiting water conditions in rhizotrons. KEY RESULTS: Summer dormancy was associated with higher dehydration tolerance, and negatively associated with traits conferring dehydration avoidance. Species with greater summer dormancy were characterized by greater springtime productivity, earlier reproduction, and a shallow and fine root system, which are indicative of dehydration escape. Summer dormancy was associated with an acquisitive, competitive functional strategy in spring, and a conservative strategy in summer. CONCLUSIONS: Both the escape and acquisitive springtime strategies observed in summer dormant perennial taxa are typically associated with annual grasses. California grasslands were once dominated by perennial species, but have been overtaken by non-native Mediterranean annual grasses, which are expected to be further favoured by climate change. Owing to functional similarity with these exotic annuals, it is suggested that native summer dormant taxa may play an important ecological role in the future of both natural and restored California grasslands.

Epoxycarotenoid-mediated synthesis of abscisic acid in Physcomitrella patens implicating conserved mechanisms for acclimation to hyperosmosis in embryophytes.

Plants acclimate to environmental stress signals such as cold, drought and hypersalinity, and provoke internal protective mechanisms. Abscisic acid (ABA), a carotenoid-derived phytohormone, which increases in response to the stress signals above, has been suggested to play a key role in the acclimation process in angiosperms, but the role of ABA in basal land plants such as mosses, including its biosynthetic pathways, has not been clarified. Targeted gene disruption of PpABA1, encoding zeaxanthin epoxidase in the moss Physcomitrella patens was conducted to determine the role of endogenous ABA in acclimation processes in mosses. The generated ppaba1 plants were found to accumulate only a small amount of endogenous ABA. The ppaba1 plants showed reduced osmotic acclimation capacity in correlation with reduced dehydration tolerance and accumulation of late embryogenesis abundant proteins. By contrast, cold-induced freezing tolerance was less affected in ppaba1, indicating that endogenous ABA does not play a major role in the regulation of cold acclimation in the moss. Our results suggest that the mechanisms for osmotic acclimation mediated by carotenoid-derived synthesis of ABA are conserved in embryophytes and that acquisition of the mechanisms played a crucial role in terrestrial adaptation and colonization by land plant ancestors.

What functional strategies drive drought survival and recovery of perennial species from upland grassland?

BACKGROUND AND AIMS: Extreme climatic events such as severe droughts are expected to increase with climate change and to limit grassland perennity. The present study aimed to characterize the adaptive responses by which temperate herbaceous grassland species resist, survive and recover from a severe drought and to explore the relationships between plant resource use and drought resistance strategies. METHODS: Monocultures of six native perennial species from upland grasslands and one Mediterranean drought-resistant cultivar were compared under semi-controlled and non-limiting rooting depth conditions. Above- and below-ground traits were measured under irrigation in spring and during drought in summer (50 d of withholding water) in order to characterize resource use and drought resistance strategies. Plants were then rehydrated and assessed for survival (after 15 d) and recovery (after 1 year). KEY RESULTS: Dehydration avoidance through water uptake was associated with species that had deep roots (>1·2 m) and high root mass (>4 kg m(-3)). Cell membrane stability ensuring dehydration tolerance of roots and meristems was positively correlated with fructan content and negatively correlated with sucrose content. Species that survived and recovered best combined high resource acquisition in spring (leaf elongation rate >9 mm d(-1) and rooting depth >1·2 m) with both high dehydration avoidance and tolerance strategies. CONCLUSIONS: Most of the native forage species, dominant in upland grassland, were able to survive and recover from extreme drought, but with various time lags. Overall the results suggest that the wide range of interspecific functional strategies for coping with drought may enhance the resilience of upland grassland plant communities under extreme drought events.

RhNAC3, a stress-associated NAC transcription factor, has a role in dehydration tolerance through regulating osmotic stress-related genes in rose petals.

Petal cell expansion depends on cell wall metabolism, changes in cell turgor pressure and restructuring of the cytoskeleton, and recovery ability of petal cell expansion is defined as an indicator of dehydration tolerance in flowers. We previously reported that RhNAC2, a development-related NAC domain transcription factor, confers dehydration tolerance through regulating cell wall-related genes in rose petals. Here, we identify RhNAC3, a novel rose SNAC gene, and its expression in petals induced by dehydration, wounding, exogenous ethylene and abscisic acid (ABA). Expression studies in Arabidopsis protoplasts and yeast show that RhNAC3 has transactivation activity along its full length and in the carboxyl-terminal domain. Silencing RhNAC3 in rose petals by virus-induced gene silencing (VIGS) significantly decreased the cell expansion of rose petals under rehydration conditions. In total, 24 of 27 osmotic stress-related genes were down-regulated in RhNAC3-silenced rose petals, while only 4 of 22 cell expansion-related genes were down-regulated. Overexpression of RhNAC3 in Arabidopsis gave improved drought tolerance, with lower water loss of leaves in transgenic plants. Arabidopsis ATH1 microarray analysis showed that RhNAC3 regulated the expression of stress-responsive genes in overexpressing lines, and further analysis revealed that most of the RhNAC3-up-regulated genes were involved in the response to osmotic stress. Comparative analysis revealed that different transcription regulation existed between RhNAC3 and RhNAC2. Taken together, these data indicate that RhNAC3, as a positive regulator, confers dehydration tolerance of rose petals mainly through regulating osmotic adjustment-associated genes.

Sex-specific divergence for body size and desiccation-related traits in Drosophila hydei from the western Himalayas.

Sex-specific-differences are a widespread source of genetic variation in various Drosophila species. In the present study, we have examined desiccation survival in males and females of Drosophila hydei from colder and drier montane conditions of the western Himalayas (altitudinal populations; 600-2202 m). In contrast with most other studies in drosophilids, D. hydei males exhibited comparatively higher desiccation resistance despite smaller body size compared to females. Accordingly, we tested the physiological basis of such adaptations in both sexes of D. hydei. Body size traits (wing length, wet weight and dry weight) were ~1.2 fold higher in females than males. However, desiccation resistance was 10 to 13 h higher in males than females. These differences matched enhanced storage of trehalose content (~1.2 fold), higher hemolymph content (~1.2 fold) and enhanced cuticular lipid mass (~1.5 fold) in males than females. Water loss before succumbing to death (dehydration tolerance) was much higher in males (~81%) than females (~64%). A greater loss of hemolymph water until death under desiccation stress was associated with higher desiccation resistance in males. Further, there were lacks of differences in the rate of water loss, rate of trehalose utilization and rate of hemolymph depletion between the sexes in D. hydei. Therefore, sex-specific differences in desiccation resistance of D. hydei were independent of body size as well as the exhaustion of metabolite reserves and rather were caused by the higher dehydration tolerance as well as higher acquisition of hemolymph and trehalose contents.

Dehydration-responsive cytoskeleton proteome of rice reveals reprograming of key molecular pathways to mediate metabolic adaptation and cell survival.

The plant cytoskeletal proteins play a key role that control cytoskeleton dynamics, contributing to crucial biological processes such as cell wall morphogenesis, stomatal conductance and abscisic acid accumulation in repercussion to water-deficit stress or dehydration. Yet, it is still completely unknown which specific biochemical processes and regulatory mechanisms the cytoskeleton uses to drive dehydration tolerance. To better understand the role of cytoskeleton, we developed the dehydration-responsive cytoskeletal proteome map of a resilient rice cultivar. Initially, four-week-old rice plants were exposed to progressive dehydration, and the magnitude of dehydration-induced compensatory physiological responses was monitored in terms of physicochemical indices. The organelle fractionation in conjunction with label-free quantitative proteome analysis led to the identification of 955 dehydration-responsive cytoskeletal proteins (DRCPs). To our knowledge, this is the first report of a stress-responsive plant cytoskeletal proteome, representing the largest inventory of cytoskeleton and cytoskeleton-associated proteins. The DRCPs were apparently involved in a wide array of intra-cellular molecules transportation, organelles positioning, cytoskeleton organization followed by different metabolic processes including amino acid metabolism. These findings presented open a unique view on global regulation of plant cytoskeletal proteome is intimately linked to cellular metabolic rewiring of adaptive responses, and potentially confer dehydration tolerance, especially in rice, and other crop species, in general.

Turgor loss point predicts survival responses to experimental and natural drought in tropical tree seedlings.

Identifying key traits that can serve as proxies for species drought resistance is crucial for predicting and mitigating the effects of climate change in diverse plant communities. Turgor loss point (πtlp ) is a recently emerged trait that has been linked to species distributions across gradients of water availability. However, a direct relationship between πtlp and species ability to survive drought has yet to be established for woody species. Using a manipulative field experiment to quantify species drought resistance (i.e., their survival response to drought), combined with measurements of πtlp for 16 tree species, we show a negative relationship between πtlp and seedling drought resistance. Using long-term forest plot data, we also show that πtlp predicts seedling survival responses to a severe El Niño-related drought, although additional factors are clearly also important. Our study demonstrates that species with lower πtlp exhibit higher survival under both experimental and natural drought. These results provide a missing cornerstone in the assessment of the traits underlying drought resistance in woody species and strengthen πtlp as a proxy for evaluating which species will lose or win under projections of exacerbating drought regimes.

Highly Stretchable, Adhesive Ionic Liquid-Containing Nanocomposite Hydrogel for Self-Powered Multifunctional Strain Sensors with Temperature Tolerance.

The demand for wearable sensors consisting of multifunctional conductive hydrogels with fatigue resistance and adhesion properties is rising. More importantly, it is necessary to improve the freezing tolerance and dehydration resistance of hydrogels to avoid performance degradation in harsh environments. Herein, a robust nanocomposite ionogel was fabricated in [EMIM][Cl] ionic liquid and clay nanosheets were used as physical cross-linkers through rapid UV polymerization. The excellent mechanical properties, repeated self-adhesion to various substrates, freezing tolerance, and anti-drying properties were integrated into the nanocomposite ionic liquid hydrogel. The addition of clay nanosheets Laponite XLG endowed the ionogel with a high stretchability of up to 1200% and a tensile strength of up to 0.14 MPa, and the ionogel could be recovered when the external force was released. Ascribing to ionic liquids, the nanocomposite ionogel displayed ionic conductivity and temperature tolerance. An ionogel battery with a 0.72 V output voltage was formed by assembling the ionogel with a layer of zinc and copper sheet on each side to realize the conversion from chemical energy to electrical energy. The maximum voltage could reach 2.8 V when the four units are combined, which could provide energy for an LED bulb and could be used as a self-powered strain sensor under harsh conditions. In this work, a multifunctional ionogel self-powered sensor is proposed, which has potential applications in the fields of electronic skin, human-machine interaction, and biosensors over a wide temperature range.