Mechanisms Of Drought Tolerance Research Articles

Transcriptomic analysis reveals mechanisms for the different drought tolerance of sweet potatoes.

Drought is a common environmental stress with great negative impacts on plant growth, development and geographical distribution as well as agriculture and food production. Sweet potato is characterized by starchy, fresh and pigmented tuber, and is regarded as the seventh most important food crop. However, there has been no comprehensive study of the drought tolerance mechanism of different sweet potato cultivars to date. Here, we studied the mechanism for drought response of seven sweet potato drought-tolerant cultivars using the drought coefficients, physiological indicators and transcriptome sequencing. The seven sweet potato cultivars were classified into four groups of drought tolerance performance. A large number of new genes and transcripts were identified, with an average of about 8000 new genes per sample. Alternative splicing events in sweet potato, which were dominated by first exon and last exon alternative splicing, were not conserved among different cultivars and not significantly affected by drought stress. Furthermore, different drought-tolerance mechanisms were revealed through differentially expressed gene analysis and functional annotation. Two drought-sensitive cultivars, Shangshu-9 and Xushu-22, mainly resisted drought stress by up-regulating plant signal transduction. The other drought-sensitive cultivar Jishu-26 responded to drought stress by down-regulating isoquinoline alkaloid biosynthesis and nitrogen/carbohydrate metabolism. In addition, the drought-tolerant cultivar Chaoshu-1 and drought-preferred cultivar Z15-1 only shared 9% of differentially expressed genes, as well as many opposite metabolic pathways in response to drought. They mainly regulated flavonoid and carbohydrate biosynthesis/metabolism in response to drought, while Z15-1 increased photosynthesis and carbon fixation capacity. The other drought-tolerant cultivar Xushu-18 responded to drought stress by regulating the isoquinoline alkaloid biosynthesis and nitrogen/carbohydrate metabolism. The extremely drought-tolerant cultivar Xuzi-8 was almost unaffected by drought stress and responded to drought environment only by regulating the cell wall. These findings provide important information for the selection of sweet potatoes for specific purposes.

Transcriptome analysis of drought-responsive and drought-tolerant mechanisms in maize leaves under drought stress.

Maize is a major crop essential for food and feed, but its production is threatened by various biotic and abiotic stresses. Drought is one of the most common abiotic stresses, causing severe crop yield reduction. Although several studies have been devoted to selecting drought-tolerant maize lines and detecting the drought-responsive mechanism of maize, the transcriptomic differences between drought-tolerant and drought-susceptible maize lines are still largely unknown. In our study, RNA-seq was performed on leaves of the drought-tolerant line W9706 and the drought-susceptible line B73 after drought treatment. We identified 3147 differentially expressed genes (DEGs) between these two lines. The upregulated DEGs in W9706 were enriched in specific processes, including ABA signaling, wax biosynthesis, CHO metabolism, signal transduction and brassinosteroid biosynthesis-related processes, while the downregulated DEGs were enriched in specific processes, such as stomatal movement. Altogether, transcriptomic analysis suggests that the different drought resistances were correlated with the differential expression of genes, while the drought tolerance of W9706 is due to the more rapid response to stimulus, higher water retention capacity and stable cellular environment under water deficit conditions.

Metabolomics reveals arbuscular mycorrhizal fungi-mediated tolerance of walnut to soil drought

BackgroundArbuscular mycorrhizal fungi (AMF) have a positive effect on drought tolerance of plants after establishing reciprocal resymbiosis with roots, while the underlying mechanism is not deciphered. Metabolomics can explain the mechanism of plant response to environmental stress by analyzing the changes of all small molecular weight metabolites. The purpose of this study was to use Ultra High Performance Liquid Chromatography Q Exactive Mass Spectrometer to analyze changes in root metabolites of walnut (Juglans regia) after inoculation with an arbuscular mycorrhizal fungus Diversispora spurca under well-watered (WW) and drought stress (DS).ResultsSixty days of soil drought significantly inhibited root mycorrhizal colonization rate, shoot and root biomass production, and leaf water potential in walnut, while AMF inoculation significantly increased biomass production and leaf water potential, accompanied by a higher increase magnitude under DS versus under WW. A total of 3278 metabolites were identified. Under WW, AMF inoculation up-regulated 172 metabolites and down-regulated 61 metabolites, along with no changes in 1104 metabolites. However, under DS, AMF inoculation up-regulated 49 metabolites and down-regulated 116 metabolites, coupled with no changes in 1172 metabolites. Among them, juglone (a quinone found in walnuts) as the first ranked differential metabolite was up-regulated by AMF under WW but not under DS; 2,3,5-trihydroxy-5–7-dimethoxyflavanone as the first ranked differential metabolite was increased by AMF under DS but not under WW. The KEGG annotation showed a large number of metabolic pathways triggered by AMF, accompanied by different metabolic pathways under WW and DS. Among them, oxidative phosphorylation and phenylalanine metabolism and biosynthesis were triggered by AMF in response to WW and DS, where N-acetyl-L-phenylalanine was induced by AMF to increase under DS, while decreasing under WW.ConclusionThis study provides new insights into the metabolic mechanisms of mycorrhiza-enhanced drought tolerance in walnuts.

Physiological, biochemical and molecular responses associated with drought tolerance in grafted grapevine

BackgroundGrafting is one of the promising techniques for improving abiotic stress tolerance in horticultural crops, but the underlying regulatory mechanisms of drought on grafted grapevine are largely unexplored.ResultsHerein, we investigated the phenotypic, physiologic, biochemical, and drought related genes change of self-rooted 1103P (1103 Paulsen), SM (Shine Muscat) and grafted SM/1103P (SM shoot/1103P root) under drought stress condition. The results indicated that grafted grapevine effectively alleviated drought damage in grape leaves by higher RWC, water potential and free water content. Drought stress led to the alterations of chlorophyll, carotenoid, photosynthetic parameters and chlorophyll fluorescence in grapevine leaves after drought treatment indicated grafted plants improved the photosystem response to drought stress. Moreover, grafted plants under drought stress exhibited higher levels of abscisic acid (ABA), indoleacetic acid (IAA) and soluble protein, but less contents of hydrogen peroxide (H2O2) and malondialdehyde (MDA) both in leaves and roots. Drought stress also increased the activities of antioxidant enzymes (SOD, POD and CAT) and activated the transcript expression of VvCu/ZnSOD, VvPOD4 and VvCAT1) in both leaves and roots. Further expression analysis by real-time PCR indicated that the expression levels of ABA-dependent and ABA-independent related genes could be activated in grafted grape after drought treatment.ConclusionsTaken together, our findings demonstrated that grafting onto 1103P enhanced tolerance against drought stress in grape by improving water content, photosynthesis and antioxidant defense capacity, which provided a valuable information for understanding the mechanisms of drought tolerance regulated by grafting plants.

Strigolactone and salicylic acid regulate the expression of multiple stress-related genes and enhance the drought resistance of cherry rootstocks

Drought is one of the most significant abiotic stress factors, which disrupts plant growth and development and restricts cherry (Cerasus spp.) production. Exploring effective methods to enhance the tolerance of cherry rootstocks to drought stress is a top urgency for scions to thrive. Strigolactones (SLs) and salicylic acid (SA) have been demonstrated to participate in various biotic and abiotic stresses. In current study, the effects of SLs and SA on cherry rootstocks under drought stress were investigated. The net photosynthetic rate, the maximum quantum yield of photosystem II, and the relative water content of the rac-GR24 and SA pretreatment groups were all higher under drought stress compared with well-watered group, but the antioxidant enzyme activities were lower, indicating that they greatly increased drought resistance. RNA-Seq analysis of leaf samples treated with drought stress (T1), drought stress along with 1 mM SA (T2), 1 μM rac-GR24 (T3), and 5 μM rac-GR24 (T4) pretreatments revealed that 837, 755, 586 and 489 differentially expressed genes (DEGs), respectively. Transcriptome analysis suggested that many of DEGs were ABA-related genes (PavNCED, and PavPP2C51), stress-related transcription factors (PavWRKY, and PavMYB), antioxidant enzyme genes (PavGST and PavPOD), and osmotic adjustment genes (PavUGTs, PavSUSs, and PavSPS1). In our study, PavDBP2D, PavABCG15-like, PavPUP9, PavLOG1-like, and PavENT8 were significantly activated by drought treatment, and rac-GR24 or SA pretreatment decreased these genes expression levels under the drought stress condition. Overall, our findings will provide a basic understanding of drought tolerance in cherry rootstocks modulated by SA and SLs, as well as new insights into regulatory mechanisms of drought tolerance in woody plants.

Leaf water status and biochemical adjustments as a mechanism of drought tolerance in two contrasting wheat (Triticum aestivum L.) varieties

Leaf water status and biochemical adjustments as a mechanism of drought tolerance in two contrasting wheat (Triticum aestivum L.) varieties

Comparative transcriptomic analysis and functional characterization reveals that the class III peroxidase gene TaPRX-2A regulates drought stress tolerance in transgenic wheat.

Drought is a major abiotic stress that reduces crop yields and quality worldwide. Although some genes involved in the response to drought stress have been identified, a more in-depth understanding of the mechanisms underlying wheat tolerance to drought is needed for the control of drought tolerance. Here, we evaluated the drought tolerance of 15 wheat cultivars and measured their physiological-biochemical parameters. Our data showed that the drought tolerance of the resistant wheat cultivars was significantly higher than that of drought-sensitive cultivars, which was associated with a greater antioxidant capacity of the former. Transcriptomic analysis revealed that different mechanisms of drought tolerance exist between the wheat cultivars Ziyou 5 and Liangxing 66. Transcriptomic analysis also revealed a large number of DEGs, including those involved in flavonoid biosynthesis, phytohormone signalling, phenolamides and antioxidants. qRT-PCR was performed, and the results showed that the expression levels of TaPRX-2A were significantly different among the various wheat cultivars under drought stress. Further study revealed that overexpression of TaPRX-2A enhanced tolerance to drought stress through the maintenance of increased antioxidase activities and reductions in ROS contents. Overexpression of TaPRX-2A also increased the expression levels of stress-related genes and ABA-related genes. Taken together, our findings show that flavonoids, phytohormones, phenolamides and antioxidants are involved in the plant response to drought stress and that TaPRX-2A is a positive regulator of this response. Our study provides insights into tolerance mechanisms and highlights the potential of TaPRX-2A overexpression in enhancing drought tolerance in crop improvement programmes.

Drought stress tolerance mechanisms and their potential common indicators to salinity, insights from the wild watermelon (Citrullus lanatus): A review.

Climate change has escalated the effect of drought on crop production as it has negatively altered the environmental condition. Wild watermelon grows abundantly in the Kgalagadi desert even though the environment is characterized by minimal rainfall, high temperatures and intense sunshine during growing season. This area is also characterized by sandy soils with low water holding capacity, thus bringing about drought stress. Drought stress affects crop productivity through its effects on development and physiological functions as dictated by molecular responses. Not only one or two physiological process or genes are responsible for drought tolerance, but a combination of various factors do work together to aid crop tolerance mechanism. Various studies have shown that wild watermelon possess superior qualities that aid its survival in unfavorable conditions. These mechanisms include resilient root growth, timely stomatal closure, chlorophyll fluorescence quenching under water deficit as key physiological responses. At biochemical and molecular level, the crop responds through citrulline accumulation and expression of genes associated with drought tolerance in this species and other plants. Previous salinity stress studies involving other plants have identified citrulline accumulation and expression of some of these genes (chloroplast APX, Type-2 metallothionein), to be associated with tolerance. Emerging evidence indicates that the upstream of functional genes are the transcription factor that regulates drought and salinity stress responses as well as adaptation. In this review we discuss the drought tolerance mechanisms in watermelons and some of its common indicators to salinity at physiological, biochemical and molecular level.

Ecophysiological responses of seedlings of six dipterocarp species to short-term drought in Borneo

To predict the dynamics of tropical rainforest ecosystems in response to climate change, it is necessary to understand the drought tolerance and related mechanisms of trees in tropical rainforests. In this study, we assessed the ecophysiological responses of seedlings of six dipterocarp species (Dipterocarpus pachyphyllus, Dryobalanops aromatica, Shorea beccariana, S. curtisii, S. parvifolia, and S. smithiana) to experimental short-term drought conditions. The seedlings were initially grown in plastic pots with sufficient irrigation; irrigation was then stopped to induce drought. Throughout the soil-drying period, we measured various ecophysiological parameters, such as maximum photosynthetic and transpiration rates, stomatal conductance, water-use efficiency, predawn water potential, the maximum quantum yield of photosystem II (Fv/Fm), leaf water characteristics (using pressure-volume curves), leaf water content, and total sugar and starch contents. In all six dipterocarp species studied, the Fv/Fm values dropped sharply when the soil water content fell below 8%. However, there were interspecific differences in physiological responses to such a decrease in soil water content: S. parvifolia and S. beccariana actively controlled their stomata during drought to reduce water consumption via an isohydric response, but showed an increase (S. parvifolia) or no change (S. beccariana) in leaf drought tolerance; Di. pachyphyllus and Dry. aromatica maintained photosynthesis and transpiration close to the wilting point during drought without reducing water consumption via an anisohydric response, and also increased their leaf drought tolerance over the drying period; and S. curtisii and S. smithiana maintained their photosynthetic capacity without stomatal closure, but showed no change or a slight decrease in leaf drought tolerance. Our results indicate that extreme drought can cause the death of dipterocarp seedlings via various drought response, which could substantially impact the future distribution, population dynamics, and structure of tropical rainforests.

Genotypic variation in water relations and gas exchange of urban trees in Detroit, Michigan, USA

Increasing tree species diversity has become a key underpinning for communities to improve resilience of urban and community forests. Increasingly, urban forestry researchers are examining physiological traits to aid in selecting trees for urban sites. Knowledge of physiological responses also has implications for understanding species’ resilience to increased stresses associated with climate change. Here, we compare growth, leaf SPAD chlorophyll index, water relations, and gas exchange of seven genotypes of shade trees planted in two locations in downtown Detroit, MI, USA. Genotypes included Redpointe® maple (Acer rubrum ‘Frank Jr.’), Flashfire® maple (Acer saccharum ‘JFS-Caddo2′), Pacific Sunset® maple (Acer truncatum x platanoides ‘Warrenred’), Emerald City® tulip tree (Liriodendron tulipifera ‘JFS-Oz’), Chanticleer® pear (Pyrus calleryana ‘Glen’s Form’), swamp white oak (Quercus bicolor), and Emerald Sunshine® elm (Ulmus propinqua ‘JFS-Bieberich’). Trees were planted in either Lafayette Plaisance Park (Park), a large urban greenspace, or on the median of St. Aubin Avenue (Median), a nearby major thoroughfare. Tree height growth and leaf SPAD index were higher for trees planted in the Park location than on the Median. However, genotypic variation was larger than the effects of location or the interaction of Genotype × Location for most traits. Across measurement dates, midday leaf water potential was lowest for Pyrus trees and highest for Ulmus and Liriodendron trees. Pyrus and Quercus trees had relatively high rates of net photosynthesis (A) and stomatal conductance (gs) while Liriodendron, Acer saccharum, and Ulmus trees had low rates of A and gs. Liriodendron trees closed their stomata rapidly as leaf water potential (Ψw) declined (isohydric response), while Pyrus and Quercus trees maintained gs across a range of leaf Ψw (anisohydric response). Liriodendron trees also had the highest relative growth rates, suggesting that drought stress avoidance through isohydry is a viable drought tolerance mechanism in urban trees.

Response of Cotton Genotypes to Water-deficit Stress using Drought Tolerance Indices and Principal Component Analysis

Drought impacts on cotton cultivation and production are expected to worsen as a result of global warming and water-deficit stress. Drought tolerance indices and PCA analysis were used to evaluate drought stress responses in eleven cotton genotypes and fifteen indices' ability to identify drought-tolerant genotypes under normal and drought circumstances. Seed cotton yield (Kentar feddan-1) was significantly affected by genotypes, years, and their interaction (p ≤ 0.05 or 0.01) under normal and water-deficit stress conditions, according to a combined ANOVA. Except for error variance, all genetic parameters studied for seed cotton yield were higher in normal irrigation conditions than in water-deficit stress conditions. According to PCA analysis, The STI, MP, GMP, HM, ATI, SSPI, and TOL are suitable indicators and were similar in their ability to screen, rank and detect tolerant genotypes, due to positive correlations among each other and also the highest association with seed cotton yield in both irrigation conditions. The genotypes G4, G9, and G10 (Group A) seemed to be the most drought-tolerant and cotton productive based on mean performance, GxY heatmap analysis, drought tolerance indices, and PCA analysis. The results of our study's drought tolerance indices and PCA could be useful and appropriate for studying drought tolerance mechanisms and cotton yield improvement in Egypt.

Comparative Transcriptome Analysis of Tolerant and Sensitive Genotypes of Common Bean (Phaseolus vulgaris L.) in Response to Terminal Drought Stress

We conducted a genome-wide transcriptomic analysis of three drought tolerant and sensitive genotypes of common bean to examine their transcriptional responses to terminal drought stress. We then conducted pairwise comparisons between the root and leaf transcriptomes from the resulting tissue based on combined transcriptomic data from the tolerant and sensitive genotypes. Our transcriptomic data revealed that 491 (6.4%) DEGs (differentially expressed genes) were upregulated in tolerant genotypes, whereas they were downregulated in sensitive genotypes; likewise, 396 (5.1%) DEGs upregulated in sensitive genotypes were downregulated in tolerant genotypes. Several transcription factors, heat shock proteins, and chaperones were identified in the study. Several DEGs in drought DB (data Base) overlapped between genotypes. The GO (gene ontology) terms for biological processes showed upregulation of DEGs in tolerant genotypes for sulfate and drug transmembrane transport when compared to sensitive genotypes. A GO term for cellular components enriched with upregulated DEGs for the apoplast in tolerant genotypes. These results substantiated the temporal pattern of root growth (elongation and initiation of root growth), and ABA-mediated drought response in tolerant genotypes. KEGG (kyoto encyclopedia of genes and genomes) analysis revealed an upregulation of MAPK (mitogen activated protein kinase) signaling pathways and plant hormone signaling pathways in tolerant genotypes. As a result of this study, it will be possible to uncover the molecular mechanisms of drought tolerance in response to terminal drought stress in the field. Further, genome-wide transcriptomic analysis of both tolerant and sensitive genotypes will assist us in identifying potential genes that may contribute to improving drought tolerance in the common bean.

Genome-wide association study of drought tolerance traits in sugar beet germplasms at the seedling stage.

Introduction: Sugar beets are an important crop for global sugar production. Intense drought and the increasing lack of water resources pose a great threat to sugar beet cultivation. It is a priority to investigate favourable germplasms and functional genes to improve the breeding of drought tolerant plants. Methods: Thus, in this study, 328 sugar beet germplasms were used in a genome-wide association study (GWAS) to identify single nucleotide polymorphism (SNP) markers and candidate genes associated with drought tolerance. Results: The results showed that under drought stress (9% PEG-6000), there were 11 significantly associated loci on chromosomes 2, 3, 5, 7, and 9 from the 108946 SNPs filtered using a mixed linear model (MLM). Genome-wide association analysis combined with qRT-PCR identified 13 genes that were significantly differentially expressed in drought-tolerant extreme materials. Discussion: These candidate genes mainly exhibited functions such as regulating sugar metabolism, maintaining internal environmental stability and participating in photosystem repair. This study provides valuable information for exploring the molecular mechanisms of drought tolerance and improvement in sugar beet.

Metabolomic analysis reveals key metabolites and metabolic pathways in Suaeda salsa under salt and drought stress.

Suaeda salsa is an important salt- and drought-tolerant plant with important ecological restoration roles. However, little is known about its underlying molecular regulatory mechanisms. Therefore, understanding the response mechanisms of plants to salt and drought stress is of great importance. In this study, metabolomics analysis was performed to evaluate the effects of salt and drought stress on S. salsa . The experiment consisted of three treatments: (1) control (CK); (2) salt stress (Ps); and (3) drought stress (Pd). The results showed that compared with the control group, S. salsa showed significant differences in phenotypes under salt and drought stress conditions. First, a total of 207 and 292 differential metabolites were identified in the Ps/CK and Pd/CK groups, respectively. Second, some soluble sugars and amino acids, such as raffinose, maltopentoses, D -altro-beptulose, D -proline, valine-proline, proline, tryptophan and glycine-L -leucine, showed increased activity under salt and drought stress conditions, suggesting that these metabolites may be responsible for salt and drought resistance in S. salsa . Third, the flavonoid biosynthetic and phenylalanine metabolic pathways were significantly enriched under both salt and drought stress conditions, indicating that these two metabolic pathways play important roles in salt and drought stress resistance in S. salsa . The findings of this study provide new insights into the salt and drought tolerance mechanisms of S. salsa .

Analysis of Transgenic Cotton Plants Containing Universal Stress Protein (GaUSP-1, GaUSP-2) and Zinc Finger Transcriptional Factor (GaZnF) Genes under Drought Stress.

Water is the most limiting factor for plant growth and crop productivity. Drought stress adversely affects crop yield throughout the world. Up to 50% of crop yield in Pakistan is severely affected by the shortage of water. Cotton is an important cash crop for Pakistan known as "white gold." It accounts for 8.2% of the value added in agriculture and about 3.2% of GDP. Besides, being the world's fourth-largest cotton producer, our yield per acre ranks 13th in the world. If we look at the Pakistan scenario, water deficiency is one of the major yield-limiting factors. Limitations related to conventional breeding and the advancements in plant genomics and biotechnology applications have opened new horizons to plant improvements. Therefore, in the current study, we carry out a comparative analysis to evaluate the morphological, physiological biochemical and molecular parameters in transgenic plants containing GaUSP-1, GaUSP-2 and GaZinc Finger genes under different drought stress conditions. Data showed that transgenic plants showed more tolerance as compared to non-transgenic plants. Transgenic and non-transgenic assist us in our better understanding of the drought-responsive mechanism and its effect on different plant growth traits, so, in this way, we would be able to explore drought tolerance mechanism and this will open the doors for the identification of drought-related genes.

Construction of a Hierarchical Gene Regulatory Network to Reveal the Drought Tolerance Mechanism of Shanxin Poplar

Drought stress is a common adverse environment that plants encounter, and many drought-tolerant genes have been characterized. The gene regulatory network (GRN) is important in revealing the drought tolerance mechanism. Here, to investigate the regulatory mechanism of Shanxin poplar (Populus davidiana × P. bolleana) responding to drought stress, a three-layered GRN was built, and the regulatory relationship between genes in the GRN were predicted from expression correlation using a partial correlation coefficient-based algorithm. The GRN contains 1869 regulatory relationships, and includes 11 and 19 transcription factors (TFs) in the first and second layers, respectively, and 158 structural genes in the bottom layers involved in eight enriched biological processes. ChIP-PCR and qRT-PCR based on transient transformation were performed to validate the reliability of the GRN. About 88.0% of predicted interactions between the first and second layers, and 82.0% of predicted interactions between the second and third layers were correct, suggesting that the GRN is reliable. Six TFs were randomly selected from the top layer for characterizing their function in drought, and all of these TFs can confer drought tolerance. The important biological processes related to drought tolerance were identified, including "response to jasmonic acid", "response to oxidative stress", and "response to osmotic stress". In this GRN, PdbERF3 is predicted to play an important role in drought tolerance. Our data revealed the key regulators, TF-DNA interactions, and the main biological processes involved in adaption of drought stress in Shanxin poplar.

Assessment of genotype by year interaction for yield components and physiological traits in cotton under drought stress using multivariate analysis and genetic parameters

The objective of this study was to identify genotype high yielding and drought-tolerant, by understanding the interaction GY pattern for yield, yield components and physiological traits in 24 cotton genotypes over five years under drought stress conditions using AMMI analysis, genetic parameters and multivariate analysis. All assessed traits were significantly impacted by genotypes and GY interaction using the AMMI model, with the exception of chlorophyll b by GY interaction. Meanwhile, seed cotton yield/plant, number of open bolls/plant, lint percentage, lint cotton yield/plant, and number of fruiting branches/plant were significantly affected by the year's factor. High BSH coupled with high GAM% was observed for all studied traits, indicating the heritability due to additive type of gene action and, the importance of these genotypes and the possibility of effective selection for drought-tolerant genotype development. A statistically significant correlation was discovered between cotton yield and most investigated traits under drought stress conditions. Direct selection can be done through these traits based on genetic parameters and Pearson's correlations analyses, which will be effective for drought tolerance and enhancing cotton yield. The results of our study's Pearson's correlation analysis, PCA and cluster analysis could be relevant and appropriate for studying drought tolerance mechanisms and cotton yield improvement. According to PCA and cluster analysis, the genotypes G20 and G19 followed by G5, G4 and G21 genotypes showed the best performance in response to drought stress regarding the yield, yield components and physiological-related traits. The previous genotypes could be used in future cotton breeding efforts in Egypt to promote drought tolerance, improve cotton productivity, and sustainable production during drought stress conditions.

Comparative Gene Enrichment Analysis for Drought Tolerance in Contrasting Maize Genotype.

Drought stress is a significant abiotic factor influencing maize growth and development. Understanding the molecular mechanism of drought tolerance is critical to develop the drought tolerant genotype. The identification of the stress responsive gene is the first step to developing a drought tolerant genotype. The aim of the current research was to pinpoint the genes that are essential for conserved samples in maize drought tolerance. In the current study, inbred lines of maize, 478 and H21, a drought-tolerant and susceptible line, were cultivated in the field and various treatments were applied. The circumstances during the vegetative stage (severe drought, moderate drought and well-watered environments) and RNA sequencing were used to look into their origins. In 478, 68%, 48% and 32% of drought-responsive genes (DRGs) were found, with 63% of DRGs in moderate drought and severe drought conditions in H21, respectively. Gene ontology (GO) keywords were explicitly enriched in the DRGs of H21, which were considerably over-represented in the two lines. According to the results of the GSEA, "phenylpropanoid biosynthesis" was exclusively enriched in H21, but "starch and sucrose metabolism" and "plant hormone signal transduction" were enhanced in both of the two lines. Further investigation found that the various expression patterns of genes linked to the trehalose biosynthesis pathway, reactive oxygen scavenging, and transcription factors, may have a role in maize's ability to withstand drought. Our findings illuminate the molecular ways that respond to lack and offer gene resources for maize drought resistance. Similarly, SNP and correlation analysis gave us noticeable results that urged us to do the same kind of analysis on other crops. Additionally, we isolated particular transcription factors that could control the expression of genes associated to photosynthesis and leaf senescence. According to our findings, a key factor in tolerance is the equilibrium between the induction of leaf senescence and the preservation of photosynthesis under drought.

Rubber Genotypes with Contrasting Drought Factor Index Revealed Different Mechanisms for Drought Resistance in Hevea brasiliensis.

It is predicted that drought will be more frequent and sustained in the future, which may affect the decline of rubber tree production. Therefore, it is critical to research some of the variables related to the drought-resistance mechanism of the rubber tree. As a result, it can be used to guide the selection of new rubber drought-resistance clones. The goal of this study was to identify drought-resistance mechanisms in rubber clones from the high drought factor index (DFI) group using ecophysiological and biochemical variables. The treatments consist of two factors, namely water deficit and contrasting clones based on the DFI variable. The first factor consisted of three levels, namely normal (fraction of transpirable soil water (FTSW) > 0.75), severe water deficit (0.1 < FTSW < 0.20), and recovery condition (FTSW > 0.75 after rewatering). The second factor consisted of seven clones, namely clones G239, GT1 (low DFI), G127, SP 217, PB 260 (moderate DFI), as well as G206 and RRIM 600 (high DFI). RRIM 600 had the highest DFI among the other clones as a drought-tolerance mechanism characteristic. Furthermore, clones RRIM 600, GT1, and G127 had lower stomatal conductance and transpiration rate than drought-sensitive clone PB 260. As a result, as drought avoidance mechanisms, clones RRIM 600, GT1, and G127 consume less water than clone PB 260. These findings indicated that clone RRIM 600 was a drought-resistant clone with drought tolerance and avoidance mechanisms.

Mapping and identification of QTL for agro-physiological traits in rice (Oryza sativa L.) under drought stress

Exploring novel QTLs for drought tolerance traits using a new rice genetic resource would be valuable to dissect the mechanisms underlying the complexity of the trait. Here, we used a recombinant inbred line population to detect the QTL associated with agro-physiological traits under drought stress, in particular incorporating the SNPs and 147 phenotype data, analyzed the transcript expression of genes within QTL using differential gene expression meta-analysis and qRT-PCR technique. Composite interval mapping analysis allowed the detection of 154 QTLs distributed into 66 regions, which included a large QTL cluster called ‘hotspot QTL’ that strongly associated with drought tolerance on rice chromosome 8. We found several genes within the QTL-containing regions that were highly expressed based on the meta-analysis approach. In the future, the QTL reported here may be utilized for marker-assisted breeding and the candidate drought-responsive genes could be characterized for dissecting a comprehensive molecular mechanism of drought tolerance in rice.