Transpirational Water Loss Research Articles

Impact of biostimulant and saline water on cape gooseberry (Physalis peruviana L.) in Brazil.

Production of Physalis peruviana L. has gained prominence in Northeastern Brazil. However, salinity limits the crop development in the Brazilian semiarid. Thus, this research aimed to evaluate the application of Acadian® biostimulant as mitigant of the deleterious effects of salinity on growth and gas exchange of P. peruviana plants. The experiment was combining different electrical conductivity of irrigation water (0.50, 1.23, 3.00, 4.44, and 5.50 dS m-1) and biostimulant doses (0.00, 1.45, 5.00, 8.55, and 10.00mL L-1). The main variables evaluated were plant height, stem diameter, number of leaves, root length, leaf area, specific leaf area, leaf area ratio, absolute and relative growth rate for plant height, and gas exchange. Experimental results showed that an increase in electrical conductivity of irrigation water had negatively affected the growth components and gas exchange in P. peruviana. Also, the application of seaweed-based biostimulant improves the photosynthetic capacity (43.3%), reduces transpiration rate (26.5%) and water loss by this process, further it attenuated the deleterious effects of salinity on specific leaf area, leaf area ratio, and stomatal conductance. To further elucidate the effectiveness of biostimulant application as a mitigant of salt stress, research aimed at the biochemical and enzyme activities of the plant's antioxidant system should be conducted to better understand this process.

The mechanisms of silicon on maintaining water balance under water deficit stress.

Water deficit stress severely threatens crop yield and numerous reports have shown silicon could enhance plants resistance to water deficit. One of the most important mechanisms is that silicon maintains the water balance. In this review, we summarized advanced research to elucidate the effect of silicon on plant water transport processes, including leaf water loss, vessel water transport, and root water uptake. In leaves, the deposition of silica phytolith on cuticle and stomata decreases transpirational water loss under water deficit stress. However, accumulating evidence suggest that silicon maintaining leaf water content is not through reducing water loss, but through osmotic adjustments, enhancing water transport and uptake. Enhancement of stem water transport efficiency by silicon is due to silica phytolith depositing in the cell wall of vessel tubes and pits, which support it avoiding to collapse and embolism, respectively. The improvement of root water uptake capacity by silicon acts as a key role in maintaining water balance. The underlying mechanisms include (i) enlargement of the root water uptake area, (ii) improvement of the water driving force, (iii) the prevention of water loss from root to soil, and (iv) the up-regulation of aquaporin activity. This review provides three simple models to understand the mechanism of silicon on water balance and highlights the future research area.

Bio-hydrothermal synthesis of ZnO–ZnFe2O4 nanoparticles using Psidium guajava leaf extract: Role in waste water remediation and plant immunity

Here in, an environmental friendly and chemical free bio-hydrothermal method was developed to synthesize ZnO–ZnFe2O4 nanoparticles (NPs) using Psidium guajava leaf extract. The prepared NPs effectively mediate water remediation process as well as enhance plant immunity. The phase formation, functionality, chemical composition, morphological feature and surface area of the prepared material was analyzed by XRD, XPS, TEM and BET analytical techniques. The average size of the prepared special shaped NPs was found to be 17.8 nm. The synthesized composite material is used for the removal of highly toxic Congo red (CR) and Methylene blue (MB) dyes from water by batch adsorption method. The adsorption processes follow Pseudo-second order kinetics and Langmuir isotherm models. The maximum adsorption capacity was found to be 120.32 mg/g for CR and 90.35 mg/g for MB at the solution pH = 6 and pH = 8 respectively. Strikingly, the fabricated ZnO–ZnFe2O4 NPs enhance the plant immune response and promote plant growth, potentially by preventing transpirational water loss. Specifically, the protein levels of key immune responsive genes including BAK1, FLS2, PR1, MPK3 and MPK6 were elevated for the plants treated with NPs as compared with the control plants.

Pepper ubiquitin-specific protease, CaUBP12, positively modulates dehydration resistance by enhancing CaSnRK2.6 stability.

Abscisic acid (ABA) is a plant hormone that activates adaptive mechanisms to environmental stress conditions. Plant adaptive mechanisms are complex and highly modulated processes induced by stress-responsive proteins; however, the precise mechanisms by which these processes function under adverse conditions remain unclear. Here, we isolated CaUBP12 (Capsicum annuum ubiquitin-specific protease 12) from pepper (C. annuum) leaves. We show that CaUBP12 expression is significantly induced after exposure to abiotic stress treatments. We conducted loss-of-function and gain-of-function genetic studies to elucidate the biological functions of CaUBP12 in response to ABA and dehydration stress. CaUBP12-silenced pepper plants and CaUBP12-overexpressing Arabidopsis plants displayed dehydration-sensitive and dehydration-tolerant phenotypes, respectively; these phenotypes were characterized by regulation of transpirational water loss and stomatal aperture. Under dehydration stress conditions, CaUBP12-silenced pepper plants and CaUBP12-overexpressing Arabidopsis plants exhibited lower and higher expression levels of stress-related genes, respectively, than the control plants. We isolated a CaUBP12 interaction protein, CaSnRK2.6, which is a homolog of Arabidopsis OST1; degradation of this protein was partially inhibited by CaUBP12. Similar to CaUBP12-silenced pepper plants and CaUBP12-overexpressing Arabidopsis plants, CaSnRK2.6-silenced pepper plants and CaSnRK2.6-overexpressing Arabidopsis displayed dehydration-sensitive and dehydration-tolerant phenotypes, respectively. Our findings suggest that CaUBP12 positively modulates the dehydration stress response by suppressing CaSnRK2.6 protein degradation.

Plant transpiration in constructed treatment wetland: Effects on water budget and management consequences

Plant transpiration is an important feature of wetlands with biological and hydraulic impacts. The global objective of this study was to question the influence of transpirational water losses on constructed treatment wetland water budget for a variety of wetland design and time of the year. Biomass and transpiration field measurements were carried out in constructed treatment wetlands (CTWs) submitted to oceanic climate and used for waste- or stormwater management. Measurements were carried out during spring, summer and fall. Biomass and transpiration rate were both significantly affected by season and site configuration, although the effect appears more sharply for season than for site. Transpiration can reach 26% of the incoming flow during the warmest part of the year for wastewater management CTW, when the effect on adjacent water courses is likely to be the most significant. The impact on multi-monthly water budget plummets to 2% of the incoming water volume. For stormwater CTW, transpiration can lead to strong water scarcity, virtually emptying all available water in these stochastically fed systems. As transpiration also plays a significant role in biogeochemical processes in wetlands, it seems important to design this type of ecological infrastructure in close relation with the pursued objectives, be it either the quality of outlet water (emphasis on treatment efficiency) or the quantity of outlet water (emphasis on flow regulation).

OsPUB41, a U-box E3 ubiquitin ligase, acts as a negative regulator of drought stress response in rice (Oryza Sativa L.).

OsPUB41 plays a negative role in drought stress response through the mediation of OsUBC25 and interacts with OsCLC6, suggesting a putative substrate. The notable expansion of Plant U-Box E3 ligases (PUB), compared with those in mammals, implies that PUB proteins have evolved to perform plant-specific functions. OsPUB41, a potential ortholog of CMPG1, was recently reported to regulate the cell wall degrading enzyme (CWDE)-induced innate immune response in rice. Here, we characterized the OsPUB41 gene, which encodes a dual-localized cytosolic and nuclear U-box E3 ligase in rice. OsPUB41 expression was specifically induced by dehydration among various abiotic stresses and abscisic acid (ABA) treatments. Furthermore, we revealed that the core U-box motif of OsPUB41 possesses the E3 ligase activity that can be activated by OsUBC25 in rice. The Ubi:RNAi-OsPUB41 knock-down and ospub41 suppression mutant plants exhibited enhanced tolerance to drought stress compared with the wild-type rice plants in terms of transpirational water loss, long-term dehydration response, and chlorophyll content. Moreover, the knock-down or suppression of the OsPUB41 gene did not cause adverse effect onrice yield-related traits. Yeast two-hybrid and an in vitro pull-down analyses revealed that OsCLC6, a chloride channel, is a putative substrate of OsPUB41. Overall, these results suggest that OsPUB41 acts as a negative regulator of dehydration conditions and interacts with OsCLC6, implying that it is a substrate of OsPUB41.

Floral Longevity of Paphiopedilum and Cypripedium Is Associated With Floral Morphology.

Floral longevity (FL) is an important trait influencing plant reproductive success by affecting the chance of insect pollination. However, it is still unclear which factors affect FL, and whether FL is evolutionarily associated with structural traits. Since construction costs and water loss by transpiration play a role in leaf longevity, we speculated that floral structures may affect the maintenance and loss of water in flowers and, therefore, FL. Here, we investigated the slipper orchid Paphiopedilum and Cypripedium, which are closely related, but strongly differ in their FL. To understand the evolutionary association of floral anatomical traits with FL, we used a phylogenetic independent comparative method to examine the relationships between 30 floral anatomical traits and FL in 18 species of Paphiopedilum and Cypripedium. Compared with Paphiopedilum species, Cypripedium species have lower values for floral traits related to drought tolerance and water retention capacity. Long FL was basically accompanied by the thicker epidermal and endodermal tissues of the floral stem, the thicker adaxial and abaxial epidermis of the flower, and low floral vein and stomatal densities. Vein density of the dorsal sepals and synsepals was negatively correlated with stomatal density. Our results supported the hypothesis that there was a correlation between FL and floral anatomical traits in slipper orchids. The ability to retain water in the flowers was associated with FL. These findings provide a new insight into the evolutionary association of floral traits with transpirational water loss for orchids under natural selection.

Quantification of leaf wax and cutin monomer composition in Pima (Gossypium barbadense L.) and upland (G. hirsutum L.) cotton

Climatological drought is a historic problem that limits agricultural production worldwide. Reducing transpirational water loss can conserve soil moisture and confer drought tolerance to crops by delaying their dehydration during periods of drought stress. Transpiration can be regulated by the hydrophobic plant cuticle, which coats the aerial surfaces of plants and limits water loss through non-stomatal transpiration. The cuticle is composed primarily of two lipid classes, free cuticular wax components and the polymerized cutin polyester. Many studies suggest that both waxes and cutin are important in maintaining plant water status during periods of drought. Five varieties of Pima cotton (Gossypium barbadense) and six varieties of upland cotton (G. hirsutum) were examined for variation in leaf wax and cutin composition. Wax and cutin monomers were analyzed using an Agilent 7890A gas chromatograph and a 5975C mass spectrometer (GC–MS). Results show that upland cotton produces more total wax than Pima varieties, whereas Pima cotton produces more total cutin than upland varieties. In both species, alcohols were the most abundant wax compounds and dihydroxy monobasic acids were the most abundant cutin monomers.

Effect of Floral Preservatives on Post Harvest Life of Gladiolus (Gladiolus grandiflorus L.) cv. American Beauty

A Postharvest experiment was conducted to maximize the vase life of gladiolus using different preservative solution in Department of Horticulture, Faculty of Agriculture, Annamalai University. In this experiment the treatment consisted of two preservative chemicals viz., 8-hydroxy quinoline sulphate @ 150, 300, 450 ppm and silver nitrate @ 25, 50, 75 ppm along with sucrose @ 2 and 4 per cent along with control (distilled water). The results of this experiment revealed that the maximum water uptake, transpirational loss of water, water balance, fresh weight change, percentage of opened florets, floret diameter, longevity of floret, vase life was recorded in T5 (8-HQS @ 300 ppm + sucrose 4%), when compared to control. Some parameters like optical density of vase solution, days taken for the basal floret to open in vase and the percentage of wilted florets were observed least in T5 (8-HQS @ 300 ppm + sucrose 4%). T5 (8-HQS @ 300 ppm + Sucrose 4%) solution was found best to extend the vase life of gladiolus.

Strawberry fruit skins are far more permeable to osmotic water uptake than to transpirational water loss

Water movements through the fruit skin play critical roles in many disorders of strawberry (Fragaria × ananassa Duch.) such as water soaking, cracking and shriveling. The objective was to identify the mechanisms of fruit water loss (dry skin, transpiration) and water uptake (wet skin, osmosis). Fruits were held above dried silica gel or incubated in deionized water. Water movements were quantified gravimetrically. Transpiration and osmotic uptake increased linearly with time. Abrading the thin cuticle (0.62 g m-2) increased rates of transpiration 2.6–fold, the rates of osmotic uptake 7.9-fold. The osmotic potential of the expressed juice was nearly the same for green and for white fruit but decreased in red fruit stages. Fruit turgor was low throughout development, except for green fruit. There was no relationship between the rates of water movement and fruit osmotic potential. The skin permeance for transpiration and for osmotic uptake were both high (relative to other fruit species) but were two orders of magnitude greater for osmotic uptake than for transpiration. Incubating fruit in isotonic solutions of osmolytes of different sizes resulted in increases in fruit mass that depended on the osmolyte. The rate of osmotic uptake decreased asymptotically as molecular size of the osmolyte increased. When transpiration and osmotic uptake experiments were conducted sequentially on the same fruit, the rates of transpiration were higher for fruit previously incubated in water. Fluorescence microscopy revealed considerable microcracking in a fruit previously incubated in water. Our findings indicate that the high permeance for osmotic uptake is accounted for by an extremely thin cuticle and by viscous water flow through microcracks and along polar pathways.

Pepper E3 ligase CaAIRE1 promotes ABA sensitivity and drought tolerance by degradation of protein phosphatase CaAITP1.

Plants have developed defense mechanisms to survive in extreme environmental conditions. Abscisic acid (ABA) is a key phytohormone associated with plant adaptation to environmental stress. In this study, we isolated and functionally characterized the pepper RING-type E3 ligase CaAIRE1 (Capsicum annuum ABA Induced RING-type E3 ligase 1) containing the C3HC4-type RING domain. CaAIRE1 was induced by ABA and drought, and CaAIRE1 had E3 ligase activity. CaAIRE1-silenced pepper and CaAIRE1-overexpressing Arabidopsis presented drought-sensitive and drought-tolerant phenotypes, respectively, which were accompanied by altered transpiration water loss and ABA sensitivity. Moreover, we found that CaAIRE1 interacts with and ubiquitinates the pepper type 2C protein phosphatase, CaAITP1 (Capsicum annuum CaAIRE1 Interacting Target Phosphatase 1). A cell-free degradation assay with CaAIRE1-silenced peppers and CaAIRE1-overexpressing Arabidopsis plants revealed that the CaAITP1 protein level was negatively modulated by the expression level of CaAIRE1. In contrast to CaAIRE1, CaAITP1-silenced pepper showed ABA-sensitivity phenotypes. CaAITP1-overexpressing Arabidopsis plants were the most insensitive phenotypes to ABA compared with the wild type and other pepper PP2C-overexpressing plants. Taken together, our data indicate that CaAITP1 plays a major role as a negative modulator in ABA signaling, and CaAIRE1 regulates the ABA signaling and drought response through modulation of CaAITP1 stability.

GABA signalling modulates stomatal opening to enhance plant water use efficiency and drought resilience

The non-protein amino acid γ-aminobutyric acid (GABA) has been proposed to be an ancient messenger for cellular communication conserved across biological kingdoms. GABA has well-defined signalling roles in animals; however, whilst GABA accumulates in plants under stress it has not been determined if, how, where and when GABA acts as an endogenous plant signalling molecule. Here, we establish endogenous GABA as a bona fide plant signal, acting via a mechanism not found in animals. Using Arabidopsis thaliana, we show guard cell GABA production is necessary and sufficient to reduce stomatal opening and transpirational water loss, which improves water use efficiency and drought tolerance, via negative regulation of a stomatal guard cell tonoplast-localised anion transporter. We find GABA modulation of stomata occurs in multiple plants, including dicot and monocot crops. This study highlights a role for GABA metabolism in fine tuning physiology and opens alternative avenues for improving plant stress resilience.

Overexpression of AtBBD1, Arabidopsis Bifunctional Nuclease, Confers Drought Tolerance by Enhancing the Expression of Regulatory Genes in ABA-Mediated Drought Stress Signaling.

Drought is the most serious abiotic stress, which significantly reduces crop productivity. The phytohormone ABA plays a pivotal role in regulating stomatal closing upon drought stress. Here, we characterized the physiological function of AtBBD1, which has bifunctional nuclease activity, on drought stress. We found that AtBBD1 localized to the nucleus and cytoplasm, and was expressed strongly in trichomes and stomatal guard cells of leaves, based on promoter:GUS constructs. Expression analyses revealed that AtBBD1 and AtBBD2 are induced early and strongly by ABA and drought, and that AtBBD1 is also strongly responsive to JA. We then compared phenotypes of two AtBBD1-overexpression lines (AtBBD1-OX), single knockout atbbd1, and double knockout atbbd1/atbbd2 plants under drought conditions. We did not observe any phenotypic difference among them under normal growth conditions, while OX lines had greatly enhanced drought tolerance, lower transpirational water loss, and higher proline content than the WT and KOs. Moreover, by measuring seed germination rate and the stomatal aperture after ABA treatment, we found that AtBBD1-OX and atbbd1 plants showed significantly higher and lower ABA-sensitivity, respectively, than the WT. RNA sequencing analysis of AtBBD1-OX and atbbd1 plants under PEG-induced drought stress showed that overexpression of AtBBD1 enhances the expression of key regulatory genes in the ABA-mediated drought signaling cascade, particularly by inducing genes related to ABA biosynthesis, downstream transcription factors, and other regulatory proteins, conferring AtBBD1-OXs with drought tolerance. Taken together, we suggest that AtBBD1 functions as a novel positive regulator of drought responses by enhancing the expression of ABA- and drought stress-responsive genes as well as by increasing proline content.

Abscisic Acid-Induced Stomatal Closure: An Important Component of Plant Defense Against Abiotic and Biotic Stress.

Abscisic acid (ABA) is a stress hormone that accumulates under different abiotic and biotic stresses. A typical effect of ABA on leaves is to reduce transpirational water loss by closing stomata and parallelly defend against microbes by restricting their entry through stomatal pores. ABA can also promote the accumulation of polyamines, sphingolipids, and even proline. Stomatal closure by compounds other than ABA also helps plant defense against both abiotic and biotic stress factors. Further, ABA can interact with other hormones, such as methyl jasmonate (MJ) and salicylic acid (SA). Such cross-talk can be an additional factor in plant adaptations against environmental stresses and microbial pathogens. The present review highlights the recent progress in understanding ABA’s multifaceted role under stress conditions, particularly stomatal closure. We point out the importance of reactive oxygen species (ROS), reactive carbonyl species (RCS), nitric oxide (NO), and Ca2+ in guard cells as key signaling components during the ABA-mediated short-term plant defense reactions. The rise in ROS, RCS, NO, and intracellular Ca2+ triggered by ABA can promote additional events involved in long-term adaptive measures, including gene expression, accumulation of compatible solutes to protect the cell, hypersensitive response (HR), and programmed cell death (PCD). Several pathogens can counteract and try to reopen stomata. Similarly, pathogens attempt to trigger PCD of host tissue to their benefit. Yet, ABA-induced effects independent of stomatal closure can delay the pathogen spread and infection within leaves. Stomatal closure and other ABA influences can be among the early steps of defense and a crucial component of plants’ innate immunity response. Stomatal guard cells are quite sensitive to environmental stress and are considered good model systems for signal transduction studies. Further research on the ABA-induced stomatal closure mechanism can help us design strategies for plant/crop adaptations to stress.

Asymmetric water transport in dense leaf cuticles and cuticle-inspired compositionally graded membranes

Most of the aerial organs of vascular plants are covered by a protective layer known as the cuticle, the main purpose of which is to limit transpirational water loss. Cuticles consist of an amphiphilic polyester matrix, polar polysaccharides that extend from the underlying epidermal cell wall and become less prominent towards the exterior, and hydrophobic waxes that dominate the surface. Here we report that the polarity gradient caused by this architecture renders the transport of water through astomatous olive and ivy leaf cuticles directional and that the permeation is regulated by the hydration level of the cutin-rich outer cuticular layer. We further report artificial nanocomposite membranes that are inspired by the cuticles’ compositionally graded architecture and consist of hydrophilic cellulose nanocrystals and a hydrophobic polymer. The structure and composition of these cuticle-inspired membranes can easily be varied and this enables a systematic investigation of the water transport mechanism.

Developmental pattern of grapevine (Vitis vinifera L.) berry cuticular wax: Differentiation between epicuticular crystals and underlying wax.

The grapevine berry surface is covered by a cuticle consisting of cutin and various lipophilic wax compounds. The latter build the main barrier for transpirational water loss and protect the fruit against environmental factors e.g. pests, mechanical impacts or radiation. The integrety of the fruit surface is one important key factor for post-harvest quality and storage of fruits. Nonetheless, the developmental pattern of cuticular wax was so far only investigated for a very limited number of fruits. Therefore, we performed comparative investigations on the compositional and morphological nature of epicuticular wax crystals and underlying wax during fruit development in Vitis vinifera. The main compound oleanolic acid belongs to the pentacyclic triterpenoids, which occur very early in the development in high amounts inside the cuticle. The amount increases until veraison and decreases further during ripening. In general, very-long chain aliphatic (VLCA) compounds are present in much smaller amounts and alcohols and aldehydes follow the same trend during development. In contrast, the amount of fatty acids constantly increases from fruit set to ripening while wax esters only occur in significant amount at veraison and increase further. Wax crystals at the fruit surface are solely composed of VLCAs and the morphology changes during development according to the compositional changes of the VLCA wax compounds. The remarkable compositional differences between epicuticular wax crystals and the underlying wax are important to understand in terms of studying grape-pest interactions or the influence of environmental factors, since only wax crystals directly face the environment.

Squandering water in drylands: the water-use strategy of the phreatophyte Ziziphus lotus in a groundwater-dependent ecosystem.

Water is the most limiting factor in dryland ecosystems, and plants are adapted to cope with this constraint. Particularly vulnerable are phreatophytic plants from groundwater-dependent ecosystems (GDEs) in regions that have to face water regime alterations due to the impacts of climate and land-use changes. We investigated two aspects related to the water-use strategy of a keystone species that dominates one of the few terrestrial GDEs in European drylands (Ziziphus lotus): where it obtains water and how it regulates its use. We (1) evaluated plants' water sources and use patterns using a multiple-isotope approach (δ2 H, δ18 O, and Δ13 C); (2) assessed the regulation of plant water potential by characterizing the species on an isohydric-anisohydric continuum; and (3) evaluated plants' response to increasing water stress along a depth-to-groundwater (DTGW) gradient by measuring foliar gas exchange and nutrient concentrations. Ziziphus lotus behaves as a facultative or partial phreatophyte with extreme anisohydric stomatal regulation. However, as DTGW increased, Z. lotus (1) reduced the use of groundwater, (2) reduced total water uptake, and (3) limited transpiration water loss while increasing water-use efficiency. We also found a physiological threshold at 14 m depth to groundwater, which could indicate maximum rooting length beyond which optimal plant function could not be sustained. Species such as Z. lotus survive by squandering water in drylands because of a substantial groundwater uptake. However, the identification of DTGW thresholds indicates that drawdowns in groundwater level would jeopardize the functioning of the GDE.

How to resolve the enigma of diurnal malate remobilisation from the vacuole in plants with crassulacean acid metabolism?

Opening of stomata in plants with crassulacean acid metabolism (CAM) is mainly shifted to the night period when atmospheric CO2 is fixed by phosphoenolpyruvate carboxylase and stored as malic acid in the vacuole. As such, CAM plants ameliorate transpirational water losses and display substantially higher water-use efficiency compared with C3 and C4 plants. In the past decade significant technical advances have allowed an unprecedented exploration of genomes, transcriptomes, proteomes and metabolomes of CAM plants and efforts are ongoing to engineer the CAM pathway in C3 plants. Whilst research efforts have traditionally focused on nocturnal carboxylation, less information is known regarding the drivers behind diurnal malate remobilisation from the vacuole that liberates CO2 to be fixed by RuBisCo behind closed stomata. To shed more light on this process, we provide a stoichiometric analysis to identify potentially rate-limiting steps underpinning diurnal malate mobilisation and help direct future research efforts. Within this remit we address three key questions: Q1 Does light-dependent assimilation of CO2 via RuBisCo dictate the rate of malate mobilisation? Q2: Do the enzymes responsible for malate decarboxylation limit daytime mobilisation from the vacuole? Q3: Does malate efflux from the vacuole set the pace of decarboxylation?

Overexpression of a Poplar RING-H2 Zinc Finger, Ptxerico, Confers Enhanced Drought Tolerance via Reduced Water Loss and Ion Leakage in Populus.

Drought stress is one of the major environmental problems in the growth of crops and woody perennials, but it is getting worse due to the global climate crisis. XERICO, a RING (Really Interesting New Gene) zinc-finger E3 ubiquitin ligase, has been shown to be a positive regulator of drought tolerance in plants through the control of abscisic acid (ABA) homeostasis. We characterized a poplar (Populus trichocarpa) RING protein family and identified the closest homolog of XERICO called PtXERICO. Expression of PtXERICO is induced by both salt and drought stress, and by ABA treatment in poplars. Overexpression of PtXERICO in Arabidopsis confers salt and ABA hypersensitivity in young seedlings, and enhances drought tolerance by decreasing transpirational water loss. Consistently, transgenic hybrid poplars overexpressing PtXERICO demonstrate enhanced drought tolerance with reduced transpirational water loss and ion leakage. Subsequent upregulation of genes involved in the ABA homeostasis and drought response was confirmed in both transgenic Arabidopsis and poplars. Taken together, our results suggest that PtXERICO will serve as a focal point to improve drought tolerance of woody perennials.

Activation tagging identifies Arabidopsis transcription factor AtMYB68 for heat and drought tolerance at yield determining reproductive stages.

Heat stress occurring at reproductive stages can result in significant and permanent damage to crop yields. However, previous genetic studies in understanding heat stress response and signaling were performed mostly on seedling and plants at early vegetative stages. Here we identify, using a developmentally defined, gain-of-function genetic screen with approximately 18000 Arabidopsis thaliana activation-tagged lines, a mutant that maintained productive seed set post-severe heat stress during flowering. Genome walking indicated this phenotype was caused by the insertion of 35S enhancers adjacent to a nuclear localized transcription factor AtMYB68. Subsequent overexpression analysis confirmed that AtMYB68 was responsible for the reproductive heat tolerance of the mutant. Furthermore, these transgenic Arabidopsis plants exhibited enhanced abscisic acid sensitivity at and post-germination, reduced transpirational water loss during a drought treatment, and enhanced seed yield under combined heat and drought stress during flowering. Ectopic expression of AtMYB68 in Brassica napus driven either by 35S or by heat-inducible promoter recapitulated the enhanced reproductive heat stress and drought tolerance phenotypes observed in the transgenic Arabidopsis. The improvement to heat stress is likely due to enhanced pollen viability observed in the transgenic plants. More importantly, the transgenic canola showed significant yield advantages over the non-transgenic controls in multiple locations, multiple season field trials under various drought and heat stress conditions. Together these results suggest that AtMYB68 regulate plant stress tolerance at the most important yield determining stage of plant development, and is an effective target for crop yield protection under current global climate volatility.