Project description:Abiotic stress-induced senescence in crops is a process particularly affecting the photosynthetic apparatus, decreasing photosynthetic activity and inducing chloroplast degradation. A pathway for stress-induced chloroplast degradation that involves the CHLOROPLAST VESICULATION (CV) gene was characterized in rice (Oryza sativa) plants. OsCV expression was up-regulated with the age of the plants and when plants were exposed to water-deficit conditions. The down-regulation of OsCV expression contributed to the maintenance of the chloroplast integrity under stress. OsCV-silenced plants displayed enhanced source fitness (i.e. carbon and nitrogen assimilation) and photorespiration, leading to water-deficit stress tolerance. Co-immunoprecipitation, intracellular co-localization, and bimolecular fluorescence demonstrated the in vivo interaction between OsCV and chloroplastic glutamine synthetase (OsGS2), affecting source-sink relationships of the plants under stress. Our results would indicate that the OsCV-mediated chloroplast degradation pathway is involved in the regulation of nitrogen assimilation during stress-induced plant senescence.
Project description:Soybean plants were subjected to water deficit, heat stress, and combination of water deficit and heat stress. Flower parts, sepal, anther, ovary and stigma were collected from 8-10 different plants at R1 stage growing under three above mentioned stress conditions, and under control conditions 10 days after initiation of the stresses. Differential gene expression compared to control was studied using RNAseq method.
Project description:Under water deficit conditions, the essential macronutrient nitrogen becomes limited as a result of reduced dissolved nitrogen and root nitrogen uptake. An elevated nitrogen level might be able to mitigate these effects, integrated with the idea of using nitric oxide as abiotic stress tolerant inducers. In this study, we evaluated the potential of using elevated nitrogen priming prior to water shortage to mitigate plant stress through nitric oxide accumulation. We grew rice plants in 300 mg L-1 nitrogen for 10 weeks, then we primed plants with four different nitrogen concentrations: 100, 300 (control), 500 and 1000 mg L-1 nitrogen prior to inducing water deficit conditions. Plants primed with 500 mg L-1 nitrogen possessed a higher photosynthetic rate, relative water content, electrolyte leakage and lipid peroxidation under water deficit conditions, compared to control plants. The induction of water deficit tolerance was supported with the activation of antioxidant defense system, induced by the accumulation of nitric oxide in leaves and roots of rice plants. We originally demonstrated the accumulation of nitric oxide in leaves of rice plants. The elevated nitrogen priming can be used to enhance water deficit tolerance in irrigated paddy fields, instead of nitric oxide donors.
Project description:BackgroundThe endophytic fungus, Neotyphodium coenophialum, can enhance drought tolerance of its host grass, tall fescue. To investigate endophyte effects on plant responses to acute water deficit stress, we did comprehensive profiling of plant metabolite levels in both shoot and root tissues of genetically identical clone pairs of tall fescue with endophyte (E+) and without endophyte (E-) in response to direct water deficit stress. The E- clones were generated by treating E+ plants with fungicide and selectively propagating single tillers. In time course studies on the E+ and E- clones, water was withheld from 0 to 5 days, during which levels of free sugars, sugar alcohols, and amino acids were determined, as were levels of some major fungal metabolites.ResultsAfter 2-3 days of withholding water, survival and tillering of re-watered plants was significantly greater for E+ than E- clones. Within two to three days of withholding water, significant endophyte effects on metabolites manifested as higher levels of free glucose, fructose, trehalose, sugar alcohols, proline and glutamic acid in shoots and roots. The fungal metabolites, mannitol and loline alkaloids, also significantly increased with water deficit.ConclusionsOur results suggest that symbiotic N. coenophialum aids in survival and recovery of tall fescue plants from water deficit, and acts in part by inducing rapid accumulation of these compatible solutes soon after imposition of stress.
Project description: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.
Project description:The plant cuticle, composed of cutin and waxes, is a hydrophobic layer coating the aerial organs of terrestrial plants and playing a critical role in limiting water loss. While melatonin has been recently demonstrated to be involved in responses to drought stress in plants, its relationship with cuticle formation is not known. In the present work, we report the effects of melatonin on the formation of cuticle in tomato leaves subjected to water deficit. Preliminary analysis by light microscope showed that tomato leaves pretreated with exogenous melatonin might have thicker cutin than tomato leaves without melatonin pretreatment under water deficit condition. Chemical characterization showed that exogenous application of melatonin increased the level of cuticular waxes in tomato leaves under water deficit. Consistent with the change in cuticular waxes was the increased abundance of wax-associated gene transcripts. Further, assessment of water loss and chlorophyll leaching in tomato leaves revealed the association of cuticle deposition with reduced leaf permeability, which is important in restricting water loss in water deficit-stressed tomato plants. These results suggest a role for melatonin in regulating leaf cuticle formation and non-stomatal water loss in leaves.
Project description:Barley (Hordeum vulgare L.), a major cereal crop grown in arid and semi-arid regions, faces significant yield variability due to drought and heat stresses. In this study, the HvABF2 gene, encoding an ABA-dependent transcription factor, was cloned using specific primers from water deficit-stressed barley seedlings. Gene expression analysis revealed high HvABF2 expression in developing caryopses and inflorescences, with significant induction under stress conditions. The HvABF2 coding sequence was utilized to generate transgenic barley plants with both stress-inducible and constitutive expression, driven by the rice SNAC1 and maize Ubiquitin promoters, respectively. Selected transgenic barley lines, along with control lines, were subjected to water deficit-stress experiments at seedling and flag leaf stages under controlled and greenhouse conditions. The transgenic lines exhibited higher relative water content and stomatal resistance under stress compared to control plants. However, constitutive overexpression of HvABF2 led to growth retardation under well-watered conditions, resulting in reduced plant height, grain weight, and grain number. In contrast, stress-inducible expression mitigated these effects, demonstrating improved drought tolerance without adverse growth impacts. This study highlights that the stress-inducible expression of HvABF2, using the SNAC1 promoter, effectively improves drought tolerance while avoiding the negative pleiotropic effects observed with constitutive expression.
Project description:Cuticular wax covers aerial organs of plants and functions as the outermost barrier against non-stomatal water loss. We reported here the functional characterization of the Glossy1(GL1)-homologous gene OsGL1-3 in rice using overexpression and RNAi transgenic rice plants. OsGL1-3 gene was ubiquitously expressed at different level in rice plants except root and its expression was up-regulated under ABA and PEG treatments. The transient expression of OsGL1-3-GFP fusion protein indicated that OsGL1-3 is mainly localized in the plasma membrane. Compared to the wild type, overexpression rice plants exhibited stunted growth, more wax crystallization on leaf surface, and significantly increased total cuticular wax load due to the prominent changes of C30-C32 aldehydes and C30 primary alcohols. While the RNAi knockdown mutant of OsGL1-3 exhibited no significant difference in plant height, but less wax crystallization and decreased total cuticular wax accumulation on leaf surface. All these evidences, together with the effects of OsGL1-3 on the expression of some wax synthesis related genes, suggest that OsGL1-3 is involved in cuticular wax biosynthesis. Overexpression of OsGL1-3 decreased chlorophyll leaching and water loss rate whereas increased tolerance to water deficit at both seedling and late-tillering stages, suggesting an important role of OsGL1-3 in drought tolerance.
Project description:The water requirements of crops should be investigated to improve the efficiency of water use in irrigated agriculture. The main objective of the study was to assess the effects of water deficit stress on rice yields throughout the major cropping seasons. We analyzed rice yield data from field experiments in Taiwan over the period 1925–2019 to evaluate the effects of water-deficit stress on the yield of 12 rice cultivars. Weather data, including air temperatures, humidity, wind speed, sunshine duration, and rainfall were used to compute the temporal trends of reference evapotranspiration and crop water status (CWS) during rice growth stages. A negative CWS value indicates that the crop is water deficient, and a smaller value represents a lower water level (greater water-deficit stress) in crop growth. The CWS on rice growth under the initial, crop development, reproductive, and maturity stages declined by 96.9, 58.9, 24.7, and 198.6 mm in the cool cropping season and declined by 63.7, 18.1, 8.6, and 3.8 mm in the warm cropping season during the 95 years. The decreasing trends in the CWSs were used to represent the increases in water-deficit stress. The total yield change related to water-deficit stress on the cultivars from 1925–1944, 1945–1983, and 1996–2019 under the initial, crop development, reproductive, and maturity stages are -56.1 to 37.0, -77.5 to -12.3, 11.2 to 19.8, and -146.4 to 39.1 kg ha-1 in the cool cropping season and -16.5 to 8.2, -12.9 to 8.1, -2.3 to 9.0, and -9.3 to 8.0 in the warm cropping season, respectively. Our results suggest that CWS may be a determining factor for rice to thrive during the developmental stage, but not the reproductive stage. In addition, the effect of water-deficit stress has increasingly affected the growth of rice in recent years.
Project description:Glycinebetaine-induced water-stress tolerance in codA-expressing transgenic indica rice is associated with up-regulation of several stress responsive genes. Rice (Oryza sativa L.), a non-accumulator of glycinebetaine (GB), is highly susceptible to abiotic stress. Transgenic rice with chloroplast-targeted choline oxidase encoded by the codA gene from Arthrobacter globiformis has been evaluated for inheritance of transgene up to R5 generation and water-stress tolerance. During seedling, vegetative and reproductive stages, transgenic plants could maintain higher activity of photosystem II and they show better physiological performance, e.g. enhanced detoxification of reactive oxygen species compared to wild-type plants under water-stress. Survival rate and agronomic performance of transgenic plants is also better than wild-type following prolonged water-stress. Choline oxidase converts choline into glycinebetaine and H2O2 in a single step. It is possible that H2O2 /GB might activate stress response pathways and prepare transgenic plants to mitigate stress. To check this possibility, microarray-based transcriptome analysis of transgenic rice has been done. It unraveled altered expression of many genes involved in stress responses, signal transduction, gene regulation, hormone signaling and cellular metabolism. Overall, 165 genes show more than 2 folds up-regulation at P value <0.01 in transgenic rice. Out of these, at least 50 genes are known to be involved in plant stress response. Exogenous application of H2O2 or GB to wild-type plants also induces such genes. Our data show that metabolic engineering for GB is a promising strategy for introducing stress tolerance in crop plants and which could be imparted, in part, by H2O2- and/or GB-induced stress response genes.