Water Stress Tolerance In Plants Research Articles

Establishment of in vitro germination of Distichlis spicata and response to osmotic stress

Abstract Distichlis spicata var. stricta (L) Greene is a grass able to grow during drought or flooding seasons, as well as in poor, saline, and alkaline soils, making it an ideal model system to study salinity and water stress tolerance in plants. However, it is known to have an extremely low germination rate in the field, as low as 3%. Here, we established in vitro conditions to study the factors that affect D. spicata under osmotic and salt stress. Treatments that included mechanical scarification, 4°C stratification, and 20% NaDCC (w/v) disinfection significantly increased the germination rate up to 84% in only 5 days. Furthermore, saltgrass had good seed germination under high salinity (ionic) stress caused by 150 and 200 mM NaCl (50% and 30%, respectively). Saltgrass was sensitive to osmotic agents Mannitol and Sorbitol during the germination stage, suggesting that this is a main limiting developmental stage for D. spicata success under osmotic environments.

Exogenous treatment with melatonin enhances waterlogging tolerance of kiwifruit plants.

Waterlogging stress has an enormous negative impact on the kiwifruit yield and quality. The protective role of exogenous melatonin on water stress has been widely studied, especially in drought stress. However, the research on melatonin-induced waterlogging tolerance is scarce. Here, we found that treatment with exogenous melatonin could effectively alleviate the damage on kiwifruit plants in response to waterlogging treatment. This was accompanied by higher antioxidant activity and lower ROS accumulation in kiwifruit roots during stress period. The detection of changes in amino acid levels of kiwifruit roots during waterlogging stress showed a possible interaction between melatonin and amino acid metabolism, which promoted the tolerance of kiwifruit plants to waterlogging. The higher levels of GABA and Pro in the roots of melatonin-treated kiwifruit plants partly contributed to their improved waterlogging tolerance. In addition, some plant hormones were also involved in the melatonin-mediated waterlogging tolerance, such as the enhancement of ACC accumulation. This study discussed the melatonin-mediated water stress tolerance of plants from the perspective of amino acid metabolism for the first time.

Improvement of water stress tolerance of plants by endophytic fungus Leptosphaeria sp. strain T-2

Improvement of water stress tolerance of plants by endophytic fungus <i>Leptosphaeria</i> sp. strain T-2

Improvement in drought tolerance in bread wheat is related to an improvement in osmolyte production, antioxidant enzyme activities, and gaseous exchange.

Water deficit stress negatively affects wheat growth, physiology, and yield. In lab and hydroponic experiments, osmotic stress levels (control, −2, −4, −6 and −8 Bars) created by PEG-6000, caused a significant decline in germination, mean germination time, root, shoot, and coleoptile length in both wheat genotypes examined. Germination was inhibited more in Wafaq-2001 than in Chakwal-50. Wafaq-2001 showed a higher susceptibility index based on root and shoot dry weight than did Chakwal-50. Wheat plants exhibited osmotic adjustment through the accumulation of proline, soluble sugars, soluble proteins, and free amino acids, and increased antioxidation activities of superoxide dismutase, peroxidase, catalase, and malondialdehyde. Increasing water deficit stress caused a linear decline in chlorophyll contents, leaf membrane stability, and relative water content in all wheat plants, with Wafaq-2001 showing a more severe negative impact on these parameters with increasing stress levels. The results suggest the possibility of utilizing some of these parameters as quantitative indicators of water stress tolerance in plants. Gas exchange measurements (photosynthesis, transpiration, stomatal conductance), leaf osmotic potential, water potential, and yield attributes decreased more abruptly with increasing water deficit, whereas leaf cuticular wax content increased in both genotypes, with more severe impacts on Wagaq-2001. More reduction in biochemical, physiological, and yield attributes was observed in Wafaq-2001 than was observed in Chakwal-50. Based on these results, we can conclude that Chakwal-50 is a more drought-tolerant genotype, and has excellent potential for future use in breeding programs to improve wheat drought tolerance.

Comparative Genomic Understanding of Gram-Positive Plant Growth-Promoting Leifsonia

Root-associated bacteria play critical roles in shaping plant health for abiotic and biotic stress tolerance. The Leifsonia genus includes pathogenic and beneficial bacteria but limited research is available comparatively across species regarding their association with plants. We recently identified the plant growth-promoting Leifsonia sp. C5G2 isolated from the rhizosphere of Plectranthus scutellarioides (coleus) that increased stress tolerance and quality of water-stressed greenhouse ornamentals. Using this beneficial strain as a model, we performed comparative genomics with beneficial, commensal, and pathogenic Leifsonia spp. to better understand plant association and growth promotion under abiotic stress. Comparative phylogenetic analyses showed that beneficial and commensal Leifsonia spp. clustered separately from pathogenic Leifsonia xyli subsp. xyli. In addition, the beneficial or commensal strains share biosynthetic gene and orthologous protein clusters that are not shared with known phytopathogens in our analysis. The phytopathogenic Leifsonia strains also share noticeably higher percent homology with plant-associated virulence factors in closely related Clavibacter spp. than the beneficial or commensal strains. Genome analysis supplemented with in vitro assays validated the findings that our model growth-promoting Leifsonia sp. strain C5G2 was highly prolific on diverse carbon sources. This is unlike known fastidious growth behaviors of phytopathogenic Leifsonia spp. Beneficial Leifsonia sp. C5G2 imparts water stress tolerance in plants, and multiple genes were identified in the genomes of beneficial Leifsonia strains that are potentially involved in bacterial osmotic stress and the production of osmoprotectants and vitamin B9. This work sheds light on the diversity of the genus Leifsonia, with a better understanding of potential mechanisms employed by poorly understood beneficial bacteria.

Melatonin-Induced Water Stress Tolerance in Plants: Recent Advances.

Water stress (drought and waterlogging) is severe abiotic stress to plant growth and development. Melatonin, a bioactive plant hormone, has been widely tested in drought situations in diverse plant species, while few studies on the role of melatonin in waterlogging stress conditions have been published. In the current review, we analyze the biostimulatory functions of melatonin on plants under both drought and waterlogging stresses. Melatonin controls the levels of reactive oxygen and nitrogen species and positively changes the molecular defense to improve plant tolerance against water stress. Moreover, the crosstalk of melatonin and other phytohormones is a key element of plant survival under drought stress, while this relationship needs further investigation under waterlogging stress. In this review, we draw the complete story of water stress on both sides—drought and waterlogging—through discussing the previous critical studies under both conditions. Moreover, we suggest several research directions, especially for waterlogging, which remains a big and vague piece of the melatonin and water stress puzzle.

Metabolomics and physiological analyses reveal β-sitosterol as an important plant growth regulator inducing tolerance to water stress in white clover

β-sitosterol influences amino acids, carbohydrates, organic acids, and other metabolite metabolism and homeostasis largely contributing to better tolerance to water stress in white clover. β-sitosterol (BS) could act as an important plant growth regulator when plants are subjected to harsh environmental conditions. Objective of this study was to examine effects of BS on growth and water stress tolerance in white clover based on physiological responses and metabolomics. White clover was pretreated with or without BS and then subjected to water stress for 7days in controlled growth chambers. Physiological analysis demonstrated that exogenous application of BS (120μM) could significantly improve stress tolerance associated with better growth performance and photosynthesis, higher leaf relative water content, and less oxidative damage in white clover in response to water stress. Metabolic profiling identified 78 core metabolites involved in amino acids, organic acids, sugars, sugar alcohols, and other metabolites in leaves of white clover. For sugars and sugar alcohol metabolism, the BS treatment enhanced the accumulation of fructose, glucose, maltose, and myo-inositol contributing to better antioxidant capacity, growth maintenance, and osmotic adjustment in white clover under water stress. The application of BS was inclined to convert glutamic acid into proline, 5-oxoproline, and chlorophyll instead of going to pyruvate and alanine; the BS treatment did not significantly affect intermediates of tricarboxylic acid cycle (citrate, aconitate, and malate), but promoted the accumulation of other organic acids including lactic acid, glycolic acid, glyceric acid, shikimic acid, galacturonic acid, and quinic acid in white clover subjected to water stress. In addition, cysteine, an important antioxidant metabolite, was also significantly improved by BS in white clover under water stress. These altered amino acids and organic acids metabolism could play important roles in growth maintenance and modulation of osmotic and redox balance against water stress in white clover. Current findings provide a new insight into BS-induced metabolic homeostasis related to growth and water stress tolerance in plants.

Differential expression of the genes involved in responses to water-deficit stress in peach trees cv. Chimarrita grafted onto two different rootstocks

ABSTRACT Water deficit is responsible for a negative impact on agricultural systems. Several physiological, biochemical, and molecular processes are initiated as a response to water-deficit stress. Quantifying the differential expression of the genes involved in the response to water-deficit stress plays a key role in the development of molecular strategies for engineering water-stress tolerance in plants. Therefore, the present study aims to evaluate the expression of key genes involved in the water-deficit response process in peach trees cv. Chimarrita grafted onto two different rootstocks. The experimental design was completely randomized, with four treatments that correspond to the evaluation periods: day zero (control), the fourth, seventh, and ninth days of water-deficit stress. Leaf samples of each Chimarrita/rootstock combination were analyzed separately. The expression of the genes related to ethylene biosynthesis, osmotic adjustment, and carbohydrate metabolism, namely ACC oxidase, GTL, SDH, SIP1, SOT1, S6PDH, and P5CS was quantified by real-time quantitative polymerase chain reaction (RT-qPCR). A differential response was observed in the expression of the SDH, GTL, P5CS, and SIP1 genes between Chimarrita/rootstock (Aldrighi 1 and Tsukuba 2)combinations. In both combinations of grafting, the S6PDH gene presented the highest level of expression at the fourth day of stress. These results show that genes related to carbohydrate and proline metabolism are important molecular markers to identify variability to water-deficit tolerance in Prunus persica.

English

English

Proline, Protein, Rwc and Msi Contents Affected by Paclobutrazol and Water Deficit Treatments in Strawberry Cv. Paros

Abstract Drought is one of the critical environmental stresses that affect growth and development of plants. Plants are damaged directly and indirectly under drought stress. Increasing water stress tolerance in plants is crucial. The aim of this study was to investigate the effects of different water stress levels (-1, -5, and -10 bars) and paclobutrazol application (0 and 50 mg-1) on strawberry cv. Paros. According to analyses of variance there were significant effects of drought stress and paclobutrazol application on leaf area, leaf dry weight, leaf relative water content (RWC), cell membrane stability index (MSI), proline and protein content of leaves. Leaf area, leaf dry weight, leaf relative water content and cell membrane stability index decreased in drought stress, especially at -10 bars. Proline and protein contents were enhanced by increasing water stress levels. Paclobutrazol application increased leaf relative water content and cell membrane stability index, proline and protein contents of leaves. Leaf relative water content was 68.77% in -10 bars drought stress that increased to 79% in paclobutrazol treatment. Also, cell membrane stability index was 69.65% in severe drought stress and reached to 77% in paclobutrazol treatment. According to the results pacloburazol is a benefit substance to ameliorate drought stress effects in strawberry cv. Paros.

Salicylic acid induces physiological and biochemical changes in three Red bayberry (Myric rubra) genotypes under water stress

Water stress is one of the main environmental stresses that affect plant growth and development. Salicylic acid (SA) induces water stress tolerance in plants. In this study, the effect of exogenous SA on physiological and biochemical process in Red bayberry (Myric rubra) seedlings, of three different genotypes, that were grown under water stress (soil ranging from 20 to 50 % of field capacity) was evaluated. Results showed that water stress severely affected the relative water content (RWC), photosynthesis, stomatal conductance and enzymes activities. Genotypes differed in RWC, Chlorophyll content, gas exchange parameter, antioxidant enzymes activities and proline, and the genotype Biqi had the RWC, photosynthesis, stomatal conductance and enzymes activities greater than the other two genotypes Wangdao and Shenhong. SA treated plants showed, in general, a higher RWC, chlorophyll content, photosynthetic rate, stomatal conductance, superoxide dismutase activity and proline content, and a lower relative electrolyte conductivity, methane dicarboxylic aldehyde content and catalase activity compared to those of untreated seedlings. These results signified the role of SA in diminishing the negative effects of drought on Red bayberry plants and suggest that SA could be used as a potential growth regulator, for improving plant growth under water stress.

Fe Binding Properties of Two Soybean (Glycine max L.) LEA4 Proteins Associated with Antioxidant Activity

Late embryogenesis abundant (LEA) group 4 (LEA4) proteins play an important role in the water stress tolerance of plants. Although they have been hypothesized to stabilize macromolecules in stressed cells, the protective functions and mechanisms of LEA4 proteins are still not clear. In this study, the metal binding properties of two related soybean LEA4 proteins, GmPM1 and GmPM9, were tested using immobilized metal ion affinity chromatography (IMAC). The metal ions Fe(3+), Ni(2+), Cu(2+) and Zn(2+) were observed to bind these two proteins, while Ca(2+), Mg(2+) or Mn(2+) did not. Results from isothermal titration calorimetry (ITC) indicated that the binding affinity of GmPM1 for Fe(3+) was stronger than that of GmPM9. Hydroxyl radicals generated by the Fe(3+)/H(2)O(2) system were scavenged by both GmPM1 and GmPM9 in the absence or the presence of high ionic conditions (100 mM NaCl), although the scavenging activity of GmPM1 was significantly greater than that of GmPM9. These results suggest that GmPM1 and GmPM9 are metal-binding proteins which may function in reducing oxidative damage induced by abiotic stress in plants.

Genetic approaches towards overcoming water deficit in plants - special emphasis on LEAs

Water deficit arises as a result of low temperature, salinity and dehydration, thereby affecting plant growth adversely and making it imperative for plants to surmount such situations by acclimatizing/adapting at various levels. Water deficit stress results in significant changes in gene expression, mediated by interconnected signal transduction pathways that may be triggered by calcium, and regulated via ABA dependent and/or independent pathways. Hence, adaptation of plants to such stresses involves maintaining cellular homeostasis, detoxification of harmful elements and also growth alterations. Stress in general cause excess production of reactive oxygen species (ROS) and the plants overcome the same by either preventing the accumulation of ROS or by eliminating the ROS formed. Ion homeostasis includes processes such as cellular uptake, sequestration and export in conjunction with long distance transport. Requisite amounts of osmolytes are hence synthesized under stress to maintain turgor along with maintaining the macromolecular structures and also for scavenging ROS. Another noteworthy response is the accumulation of novel proteins, including enzymes involved in the biosynthesis of osmoprotectants, heat-shock proteins (HSPs), late embryogenesis abundant (LEA) proteins, antifreeze proteins, chaperones, detoxification enzymes, transcription factors, kinases and phosphatases. The LEAs belong to a redundant protein family and are highly hydrophilic, boiling-soluble, non-globular and therefore have been defined and classified accordingly. The precise function of LEAs is still unknown, but substantial evidence indicates their involvement in dessication tolerance as the expression of LEAs confers increased resistance to stress in heterologous yeast system and also significantly improves water deficit tolerance in transgenic plants. Genetic manipulation of plants towards conferring abiotic stress tolerance is a daunting task, as the abiotic stress tolerance mechanism is highly complex and various strategies have been exploited to address and evaluate the stress tolerance mechanism, and the molecular responses to water deficit via complex signaling networks. Genomic technologies have recently been useful in integrating the multigenicity of the plant stress responses through, transcriptomics, proteomics and metabolite profilling and their interactions. This review deals with the recent developments on genetic approaches for water stress tolerance in plants, with special emphasis on LEAs.

Adaptations of higher plant cell walls to water loss: drought vs desiccation

Water-deficit stress poses unique challenges to plant cells dependent on a hydrostatic skeleton and a polysaccharide-rich cell wall for growth and development. How the plant cell wall is adapted to loss of water is of interest in developing a general understanding of water stress tolerance in plants and of relevance in strategies related to crop improvement. Drought tolerance involves adaptations to growth under reduced water potential and the concomitant restructuring of the cell wall that allow growth processes to occur at lower water contents. Desiccation tolerance, by contrast, is the evolution of cell walls that are capable of losing the majority of cellular water without suffering permanent and irreversible damage to cell wall structure and polymer organization. This minireview highlights common features and differences between these two water-deficit responses observed in plants, emphasizing the role of the cell wall, while suggesting future research avenues that could benefit fundamental understanding in this area.

Ectopic overexpression of wheat TaSrg6 gene confers water stress tolerance in Arabidopsis

Transcriptional regulation plays a key role in plant response to abiotic stresses. Study in barley indicated that a stress-responsive gene ( Srg6), as potential transcriptional regulator, was induced by various abiotic stresses. However, functional roles of Srg proteins in stress tolerance are unknown. In this study, we isolated a wheat homolog of barley Srg6 gene, and designated TaSrg6. Expression analysis indicated that expression of TaSrg6 gene is induced by various stress treatments, including PEG, salt, low temperature and ABA. The fusion protein GFP-TaSrg6 was concentrated in the nucleus when transiently expressed in onion epidermal cells. Overexpression of TaSrg6 gene in Arabidopsis conferred water stress tolerance in terms of survival rate, CMS value and relative water loss. We concluded that TaSrg6 protein played an important role in the enhancement of water stress tolerance in plants.

Biochemical and molecular responses to water stress in resurrection plants.

A small group of angiosperms, known as resurrection plants, can tolerate extreme dehydration. They survive in arid environments because they are able to dehydrate, remain quiescent during long periods of drought, and then resurrect upon rehydration. Dehydration induces the expression of a large number of transcripts in resurrection plants. Gene products with a putative protective function such as LEA proteins have been identified; they are expressed at high levels in the cytoplasm or in chloroplasts upon dehydration and/or ABA treatment of vegetative tissue. An increase in sugar concentration is usually observed at the onset of desiccation in vegetative tissue of resurrection plants. These sugars may be effective in osmotic adjustment or they may stabilize membrane structures and proteins. Regulatory genes such as a protein translation initiation factor, homeodomain-leucine zipper genes and a gene probably working as a regulatory RNA have been isolated and characterized. The knowledge of the biochemical and molecular responses that occur during the onset of drought may help to improve water stress tolerance in plants of agronomic importance.

Can the Quest for Drought Tolerant Crops AvoidArabidopsisAny Longer?

SUMMARY The use of Arabidopsis as a model system in plant research has been a powerful tool for biologists in the last twenty years, yet crop scientists largely have considered Arabidopsis an unsuitable system for addressing agricultural problems. The realization that Arabidopsis genes can function ectopically in other plant species, together with recent advances in our understanding of Arabidopsis gene function, have greatly facilitated the potential for genetic manipulation of crop species. Based on the available data on function in Arabidopsis and on our current knowledge of phenological, morphological, and biochemical factors affecting water stress tolerance in plants, we identify in this chapter possible strategies to improve drought stress tolerance, using the powerful genetic model Arabidopsis. Specifically, we consider those Arabidopsis genes and mutants, whose respective functions and phenotypes may be directly or indirectly involved in improving drought stress tolerance. Genes that shorten or de...

Cadmium-Induced Decrease of Water Stress Resistance in Bush Bean Plants ( Phaseolus vulgaris L. cv. Contender) I. Effects of Cd on Water Potential, Relative Water Content, and Cell Wall Elasticity

Summary The leaf water potential (ψ w ) and the relative water content (RWC) of primary and first trifoliate leaves of bean plants ( Phaseolus vulgaris L. cv. Contender), grown with different Cd concentrations in the medium, were analysed under both normal water supply and water stress conditions. With these data, Richter plots were drawn, from which the maximum turgor pressure, the turgor loss point, the bulk elastic modulus, and the structure coefficient were derived. Cd generally decreased the water stress tolerance of plants, causing turgor loss at higher RWC and ψ w than in non-treated control plants. Cd increased the bulk elastic modulus and therefore decreased the cell wall elasticity. Low cell wall elasticity seems to be an important causes of the low water stress tolerance in Cd-toxic plants.