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"Drought tolerance"
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A co-opted steroid synthesis gene, maintained in sorghum but not maize, is associated with a divergence in leaf wax chemistry
Virtually all land plants are coated in a cuticle, a waxy polyester that prevents nonstomatal water loss and is important for heat and drought tolerance. Here, we describe a likely genetic basis for a divergence in cuticular wax chemistry between
, a drought tolerant crop widely cultivated in hot climates, and its close relative
(maize). Combining chemical analyses, heterologous expression, and comparative genomics, we reveal that: 1) sorghum and maize leaf waxes are similar at the juvenile stage but, after the juvenile-to-adult transition, sorghum leaf waxes are rich in triterpenoids that are absent from maize; 2) biosynthesis of the majority of sorghum leaf triterpenoids is mediated by a gene that maize and sorghum both inherited from a common ancestor but that is only functionally maintained in sorghum; and 3) sorghum leaf triterpenoids accumulate in a spatial pattern that was previously shown to strengthen the cuticle and decrease water loss at high temperatures. These findings uncover the possibility for resurrection of a cuticular triterpenoid-synthesizing gene in maize that could create a more heat-tolerant water barrier on the plant's leaf surfaces. They also provide a fundamental understanding of sorghum leaf waxes that will inform efforts to divert surface carbon to intracellular storage for bioenergy and bioproduct innovations.
Journal Article
myo‐inositol‐1‐phosphate synthase gene, IbMIPS1, enhances salt and drought tolerance and stem nematode resistance in transgenic sweet potato
Myo‐inositol‐1‐phosphate synthase (MIPS) is a key rate limiting enzyme in myo‐inositol biosynthesis. The MIPS gene has been shown to improve tolerance to abiotic stresses in several plant species. However, its role in resistance to biotic stresses has not been reported. In this study, we found that expression of the sweet potato IbMIPS1 gene was induced by NaCl, polyethylene glycol (PEG), abscisic acid (ABA) and stem nematodes. Its overexpression significantly enhanced stem nematode resistance as well as salt and drought tolerance in transgenic sweet potato under field conditions. Transcriptome and real‐time quantitative PCR analyses showed that overexpression of IbMIPS1 up‐regulated the genes involved in inositol biosynthesis, phosphatidylinositol (PI) and ABA signalling pathways, stress responses, photosynthesis and ROS‐scavenging system under salt, drought and stem nematode stresses. Inositol, inositol‐1,4,5‐trisphosphate (IP₃), phosphatidic acid (PA), Ca²⁺, ABA, K⁺, proline and trehalose content was significantly increased, whereas malonaldehyde (MDA), Na⁺ and H₂O₂ content was significantly decreased in the transgenic plants under salt and drought stresses. After stem nematode infection, the significant increase of inositol, IP₃, PA, Ca²⁺, ABA, callose and lignin content and significant reduction of MDA content were found, and a rapid increase of H₂O₂ levels was observed, peaked at 1 to 2 days and thereafter declined in the transgenic plants. This study indicates that the IbMIPS1 gene has the potential to be used to improve the resistance to biotic and abiotic stresses in plants.
Journal Article
Seedling root morphology and biomass allocation of 62 tropical tree species in relation to drought- and shade-tolerance
1. Water availability is the main determinant of species' distribution in lowland tropical forests. Species' occurrence along water availability gradients depends on their ability to tolerate drought. 2. To identify species' traits underlying drought-tolerance we excavated first year seedlings of 62 dry and moist forest tree species at the onset of the dry season. We evaluate how morphological seedling traits differ between forests, and whether functional groups of species can be identified based on trait relations. We also compare seedling traits along independent axes of drought and shade-tolerance to assess a hypothesized trade-off. 3. Seedlings of dry forest species improve water foraging capacity in deep soil layers by an increased below-ground biomass allocation and by having deep roots. They minimize the risk of cavitation by making dense stems, and reduce transpiration by producing less leaf tissue. Moist forest seedlings have large leaf areas and a greater above-ground biomass, to maximize light interception, and long, cheap, branched root systems, to increase water and nutrient capture. 4. Associations among seedling traits reveal three major drought strategies: (i) evergreen drought-tolerant species have high biomass investment in enduring organs, minimize cavitation and minimize transpiration to persist under dry conditions; (ii) drought-avoiding species maximize resource capture during a limited growing season and then avoid stress with a deciduous leaf habit in the dry season; (iii) drought-intolerant species maximize both below- and above-ground resource capture to increase competitiveness for light, but are consequently precluded from dry habitats. 5. We found no direct trade-off between drought- and shade-tolerance, because they depend largely on different morphological adaptations. Drought-tolerance is supported by a high biomass investment to the root system, whereas shade-tolerance is mainly promoted by a low growth rate and low SLA. 6. Synthesis. We conclude that there are three general adaptation strategies of drought-tolerance, which seemingly hold true across biomes and for different life forms. Drought- and shade-tolerance are largely independent from one another, suggesting a high potential for niche differentiation, as species' specialization can occur at different combinations of water and light availability.
Journal Article
grape bHLH transcription factor gene, VvbHLH1, increases the accumulation of flavonoids and enhances salt and drought tolerance in transgenic Arabidopsis thaliana
In plants, transcriptional regulation is the most important tool for modulating flavonoid biosynthesis. The basic helix-loop-helix transcription factors are only one example how then flavonoid pathway is regulated. There are other transcription factors as well. In this study, the codon-optimized VvbHLH1 gene from grape was chemically synthesized. Overexpression of VvbHLH1 significantly increased the accumulation of flavonoids and enhanced salt and drought tolerance in transgenic Arabidopsis thaliana plants. Real-time quantitative PCR analysis showed that overexpression of VvbHLH1 resulted in the up-regulation of genes involved in flavonoid biosynthesis, abscisic acid (ABA) signaling pathway, proline biosynthesis, stress responses and ROS scavenging under salt and drought stresses. Further analyses under salt and drought stresses showed significant increases of ABA and proline content, superoxide dismutase and peroxidase activities, as well as significant reduction of hydrogen peroxide (HâOâ) and malonaldehyde content. The results demonstrate the explicit role of VvbHLH1 in conferring salt and drought tolerance by increasing the accumulation of flavonoids and ABA signalling in transgenic A. thaliana. The VvbHLH1 gene has the potential to be used to increase the content of valuable flavonoids and improve the tolerance to abiotic stresses in A. thaliana and other plants.
Journal Article
novel Cys2/His2 zinc finger protein gene from sweetpotato, IbZFP1, is involved in salt and drought tolerance in transgenic Arabidopsis
MAIN CONCLUSION : IbZFP1 , encoding a Cys ₂ /His ₂ zinc finger protein gene from sweetpotato, enhances salt and drought tolerance in transgenic Arabidopsis by regulating ABA signaling pathway, proline biosynthesis, stress responses and ROS scavenging. In plants, Cys₂/His₂ zinc finger proteins play important roles in regulating the growth and development or responses to abiotic stresses. In this study, a novel Cys₂/His₂ zinc finger protein gene, named IbZFP1, was isolated from drought-tolerant sweetpotato [Ipomoea batatas (L.) Lam.] line Xu55-2. Subcellular localization analysis in onion epidermal cells indicated that IbZFP1 was localized to the nucleus. Expression analysis in yeast showed that the full length of IbZFP1 exhibited transcriptional activation. Expression of IbZFP1 was induced by NaCl, polyethylene glycol and abscisic acid (ABA). Overexpression of IbZFP1 significantly enhanced salt and drought tolerance in transgenic Arabidopsis plants. Real-time quantitative PCR (qRT-PCR) analysis showed that overexpression of IbZFP1 up-regulated the genes involved in ABA signaling pathway, proline biosynthesis, stress responses, and ROS scavenging under salt and drought stresses. Meanwhile, Western blot and enzymatic analyses showed that the activities of 9-cis-epoxycarotenoid dioxygenase, pyrroline-5-carboxylate synthase, superoxide dismutase, catalase, ascorbate peroxidase, and peroxidase were also increased. Further component analyses indicated that the significant increase of ABA, proline, soluble sugar and total chlorophyll content and the significant reduction of H₂O₂ and malonaldehyde content were observed under salt and drought stresses. In addition, the rates of electrolyte leakage and water loss were reduced in transgenic plants. The overall results demonstrate the explicit role of IbZFP1 in conferring salt and drought tolerance in transgenic Arabidopsis plants. The IbZFP1 gene has the potential to be used to enhance the tolerance to abiotic stresses in plants.
Journal Article
Response of Maize Hybrids in Drought-Stress Using Drought Tolerance Indices
This study was conducted to investigate the response of maize hybrids to drought stress and to select the most drought-tolerant cultivar compared to other hybrids. The experiment was performed on six maize hybrids in a randomized complete block design (RCBD) with three replications under regular irrigation and limited irrigation in the vegetative and reproductive stages in Iran. Drought tolerance indices (TOL, MP, GMP, STI, SSI, and HAR) for the grain yield of genotypes were calculated, and principal component analysis was based on them. The results obtained from estimating the indices showed that the SC647 and KSC704 hybrids, while having good performance in both conditions, also have drought tolerance. Examining the correlation between drought tolerance indices and yield in both conditions, among the indices used to detect drought tolerance, STI, MP, and GMP indices can be considered suitable for selecting high-yielding hybrids in these conditions. The principal components analysis on the stress-tolerance index showed that MP and GMP indices could be used as the best indices with high coefficients to select stress-tolerance hybrids. SC647 and KSC704 hybrids were identified and selected as hybrids with high tolerance to moisture stress. The results of drought tolerance indices in the emergence stage of the crest showed that the KSC260 hybrid has the lowest level of stress sensitivity. SC647 hybrids showed the lowest susceptibility to drought stress in the ear emergence stage.
Journal Article
Enhanced Expression of AtNHX1, in Transgenic Groundnut (Arachis hypogaea L.) Improves Salt and Drought Tolerence
Salinity and drought are main threat to agriculture productivity, to avoid further losses it is necessary to improve the genetic material of crops against these stresses In this present study, AtNHX1, a vacuolar type Na+/H+ antiporter gene driven by 35S promoter was introduced into groundnut using Agrobacterium tumefaciens transformation system. The stable integration of the AtNHX1 gene was confirmed by polymerase chain reaction (PCR) and southern blot analysis. It was found that transgenic plants having AtNHX1 gene are more resistant to high concentration of salt and water deprivation than the wild type plants. Salt and proline level in the leaves of the transgenic plants were also much higher than that of wild type plants. The results showed that overexpression of AtNHX1 gene not only improved salt tolerance but also drought tolerance in transgenic groundnut. Our results suggest that these plants could be cultivated in salt and drought-affected soils.
Journal Article
Assessing future suitability of tree species under climate change by multiple methods: a case study in southern Germany
We compared results derived using three different approaches to assess the suitability of common tree species on the Franconian Plateau in southern Germany under projected warmer and drier climate conditions in the period 2061-2080. The study area is currently a relatively warm and dry region of Germany. We calculated species distribution models (SDMs) using information on species’ climate envelopes to predict regional species spectra under 63 different climate change scenarios. We complemented this with fine-scale ecological niche analysis using data from 51 vegetation surveys in seven forest reserves in the study area, and tree-ring analysis (TRA) from local populations of five tree species to quantify their sensitivity to climatic extreme years. The SDMs showed that predicted future climate change in the region remains within the climate envelope of certain species (e.g. Quercus petraea), whilst for e.g. Fagus sylvatica, future climate conditions in one third of the scenarios are too warm and dry. This was confirmed by the TRA: sensitivity to drought periods is lower for Q. petraea than for F. sylvatica. The niche analysis shows that the local ecological niches of Quercus robur and Fraxinus excelsior are mainly characterized by soils providing favorable water supply than by climate, and Pinus sylvestris (planted) is strongly influenced by light availability. The best adapted species for a warmer and potentially drier climate in the study region are Acer campestre, Sorbus torminalis, S. aria, Ulmus minor, and Tilia platyphyllos, which should therefore play a more prominent role in future climate-resilient mixed forest ecosystems.
Journal Article