Mechanisms Of Drought Tolerance Research Articles

Alternative Splicing of PheNAC23 from Moso Bamboo Impacts Flowering Regulation and Drought Tolerance in Transgenic Arabidopsis.

NAC (NAM, ATAF, and CUC) transcription factors are essential in regulating plant stress response and senescence, with their functions being modulated by alternative splicing. The molecular mechanisms of stress-induced premature flowering and drought tolerance in Phyllostachys edulis (moso bamboo) are not yet fully understood. In this study, a novel NAC variant derived from PheNAC23, named PheNAC23ES, was isolated. PheNAC23ES exhibited distinct expression patterns compared to PheNAC23 during leaf senescence and drought stress response. Overexpression of PheNAC23 promoted flowering and reduced its tolerance to drought stress in Arabidopsis thaliana (A. thaliana). However, overexpression of PheNAC23ES exhibited the opposite functions. PheNAC23 was localized in the nucleus and had transactivation activity, while PheNAC23ES had a similar localization to the control green fluorescent protein and no transactivation activity. Further functional analysis revealed that PheNAC23ES could interact with PheNAC23, suggesting that PheNAC23ES might serve as a small interfering peptide that affects the function of PheNAC23 by binding to it.

Identification of crucial drought-tolerant genes of barley through comparative transcriptomic analysis and yeast-based stress assay

Drought is a persistent and serious threat to crop yield and quality. The identification and functional characterization of drought tolerance-related genes is thus vital for efforts to support the genetic improvement of drought-tolerant crops. Barley is highly adaptable and renowned for its robust stress resistance, making it an ideal subject for efforts to explore genes related to drought tolerance. In this study, two barley materials with different drought tolerance were subjected to soil drought treatment, including a variety with strong drought tolerance (Hindmarsh) and a genotype with weaker drought tolerance (XZ5). Transcriptomic sequencing data from the aboveground parts of these plants led to the identification of 1,206 differentially expressed genes associated with drought tolerance. These genes were upregulated in Hindmarsh following drought stress exposure but downregulated or unchanged in XZ5 under these same conditions, or were unchanged in Hindmarsh but downregulated in XZ5. Pathway enrichment analyses suggested that these genes are most closely associated with defense responses, signal recognition, photosynthesis, and the biosynthesis of various secondary metabolites. Using protein-protein interaction networks, the ankyrin repeat domain-containing protein 17-like isoform X2 was predicted to impact other drought tolerance-related protein targets in Hindmarsh. In MapMan metabolic pathway analyses, genes found to be associated with the maintenance of drought tolerance in Hindmarsh under adverse conditions were predicted to include genes involved in the abscisic acid, cytokinin, and gibberellin phytohormone signaling pathways, genes associated with redox homeostasis related to ascorbate and glutathione S-transferase, transporters including ABC and AAAP, transcription factors such as AP2/ERF and bHLH, the heat shock proteins HSP60 and HSP70, and the sucrose non-fermenting-1-related protein kinase. Heterologous HvSnRK2 (one of the identified genes, which encodes the sucrose non-fermenting-1-related protein kinase) gene expression in yeast conferred significant drought tolerance, highlighting the functional importance of this gene as one linked with drought tolerance. This study revealed the drought tolerance mechanism of Hindmarsh by comparing transcriptomes while also providing a set of candidate genes for genetic efforts to improve drought tolerance in this and other crop species.

Evaluation of drought and salinity tolerance potentials of different soybean genotypes based upon physiological, biochemical, and genetic indicators

The present study has evaluated different soybean genotypes to understand the salt and drought tolerance mechanisms based on physiological traits (photosynthesis, stomatal conductance, chlorophyll, and cell membrane stability), antioxidant enzymes (superoxide dismutase, catalase, and peroxidase), reactive oxygen species (H2O2 and O2•−), osmolytes (glycine betaine, proline, and Na+/K+), plant water relations (relative water content, water potential, and solute potential) and expression of related genes (GmCAT1, GmPOD1, GmSOD, GmP5CS, GmNHX1, GmAKT1, GmDREB1, and GmARF1). The experiment was conducted in a two-factorial arrangement using randomized complete block design (RCBD) with genotypes as one factor and salt, drought, and control treatments as the other factor. All physiological traits, relative water content, and water potential decreased significantly in all soybean genotypes due to individual and combined treatments of drought and salt stress, with significantly less decrease in soybean genotypes G4620RX, DM45X61, and NARC-21. Besides that, the activity of antioxidant enzymes, production of ROS, accumulation of osmolytes, solute potential, and Na+/K+ ratio were increased significantly in all soybean genotypes under salt and water deficit conditions. As a whole, the soybean genotypes G4620RX, DM45X61, and NARC-21 showed the maximum enzymatic activity with less increase in ROS and Na+/K+ in addition to a high accumulation of osmolytes and an increase in solute potential. Correspondingly, the genotypes exhibiting high physiological and biochemical tolerance to drought and salt stresses showed the high expression of genes imparting the stress tolerance. Moreover, correlation, heatmap, and principal component analysis further confirmed the varying physiological and biochemical responses of all soybean genotypes under individual and combined applications of drought and salinity stresses. Overall, the present study confirmed that plants opt for the integrated physiological, biochemical, and genetic approaches to counteract the harmful effects of environmental stresses.

Drought tolerance mechanisms and water flux effects of oil peony in Chinese Loess Plateau

Drought tolerance mechanisms and water flux effects of oil peony in Chinese Loess Plateau

Transcriptome and molecular evidence of HvMORF8 conferring drought-tolerance in barley

Drought is one of the most devastating abiotic stresses worldwide, which severely limits crop yield. Tibetan wild barley is a treasure trove of useful genes for crop improvement including drought tolerance. Here, we detected large-scale changes of gene expression in response to drought stress with a substantial difference among contrasting Tibetan barley genotypes XZ5 (drought-tolerant), XZ54 (drought-sensitive) and cv. Tadmor (drought-tolerant). Drought stress led to upregulations of 142 genes involved in transcription, metabolism, protein synthesis, stress defense, transport and signal transduction in XZ5, but those genes were down-regulated or unchanged in XZ54 and Tadmor. We identified and functionally characterized a novel multiple organellar RNA editing factors 8 (HvMORF8), which was up-regulated by drought stress in XZ5, but unchanged in XZ54 and Tadmor under drought stress. Phylogenetic analysis showed that orthologues of HvMORF8 can be traced back to the closest gymnosperm species such as Cycas micholitzii, implicating a potential evolutionary origin for MORF8 from a common ancestor in early seed plants. Virus-induced HvMORF8 silencing in XZ5 led to hypersensitivity to drought stress, demonstrating it is a positive regulator of drought tolerance in barley. RNA sequencing of BSMV:HvMORF8 and control plants reveals that silencing of HvMORF8 suppresses genes involved in osmolytes transport, cell wall modification and antioxidants, resulting in water metabolism disorder and overaccumulation of reactive oxygen species (ROS) under drought stress. Therefore, we propose HvMORF8-mediated regulatory drought tolerance mechanisms at transcriptomic level in XZ5, providing new insight into the genetic basis of plastid RNA editing function of HvMORF8 for barley drought tolerance.

A comparison of drought responses in wild wheat relatives and domesticated wheat grown under irrigated and rainfed field conditions

ContextDomestication and breeding processes for developing modern wheat plants from diverse wild relatives and landraces have had unintended effects of loss of genetic diversity. This reduction in genetic variation undermines the ability of modern wheat cultivars to tolerate environmental stresses such as drought. Wheat wild relatives possess untapped genetic potential for tolerating abiotic stress, especially drought. Yet, their morpho-physiological adaptation and drought stress resilience mechanisms remain underexplored. ObjectiveThis study aimed to investigate the adaptive responses of plants within the Triticum spp. genepool, encompassing wheat wild relatives, landraces, and modern cultivars to drought stress under rainfed and irrigated field conditions. MethodsFrom an initial pool of 110 genotypes screened during the first growing season in 2022, 20 best performing genotypes, including modern cultivars for comparison, were selected for a second growing season in 2023 based on their relative yield performance. Two different treatment conditions, irrigated and rainfed, were applied during both growing seasons. This experiment observed single plants per replicate. Multiple parameters, including days to heading and flowering, plant height, number of spikes per plant, spike length, spike weight per plant, straw weight per plant, aboveground biomass per plant, grain yield per plant, thousand kernel weight, harvest index, stomatal conductance, and vegetation indices, were assessed on the selected genotypes. ResultsTaking averages measured across both growing seasons, we observed significant genotypic variation across several parameters: days to heading and flowering, plant height, number of spikes per plant, spike length, spike and straw weight per plant, aboveground biomass per plant, grain yield per plant, thousand kernel weight, harvest index, stomatal conductance, and vegetation indices. Water stress during the rainfed treatment significantly reduced grain yield (by 21 %) and stomatal conductance (by 45 %). Stomatal conductance was associated with grain yield and yield-related traits under rainfed conditions. Diverse physiological drought tolerance mechanisms associated with stomatal regulation were identified, revealing genotype-specific responses to drought stress. Genotypes such as T. dicoccoides (G242), T. urartu (G45), T. boeoticum (G27) and T. araraticum (G221) exhibited isohydric adaptation, whereas T. monococcum sinskajae (G89) and T. durum cv. Sambadur (G41) exhibited anisohydric adaptation. ConclusionSome genotypes of T. dicoccoides, T. urartu, T. boeoticum and T. araraticum exhibited isohydric adaptation, while T. monococcum sinskajae and T. durum cv. Sambadur exhibited anisohydric adaptation under drought stress which needs further verification. These genotypes can serve as donors for introducing drought tolerance traits within wheat improvement programs. ImplicationsThese findings holds great significance in improving drought tolerance in modern wheat breeding programs.

Physiological and biochemical changes induced by drought stress during the stem elongation and anthesis stages in the Triticum genus

Drought stress negatively influences the growth, development, and grain yield of wheat by disrupting its morphological, physiological, and biochemical processes. This study examined the effects of drought stress during the stem elongation and anthesis developmental stages of species within the Triticum genus along with their drought adaptation mechanisms under fully watered and drought conditions. We tested the following two hypotheses: (1) drought tolerance mechanisms for osmotic and stomatal regulation that lead to oxidative stress are correlated between the stem elongation and anthesis stages and affect grain yield loss, and (2) compared with modern cultivars, wild wheat cultivars exhibit greater drought tolerance. To test these hypotheses, a greenhouse pot experiment was conducted using 17 genotypes of wild wheat relatives and landraces, with modern cultivars included for comparison. Drought stress was induced during the stem elongation and anthesis stages until the average soil moisture was approximately 15 % and 18 %, respectively, of the pot’s water holding capacity. The soil moisture was maintained at 80–90 % for the fully watered treatment. An examination of physiological and biochemical traits revealed that drought significantly reduced stomatal conductance (gsw) and relative water content (RWC) during both developmental stages. However, significant increases occurred in the malondialdehyde (MDA) content during both stages and in the proline content during the anthesis stage. Drought stress significantly decreased the number of days to heading and anthesis, indicating that drought escape occurs under severe drought stress. Furthermore, drought significantly decreased morphological and yield-related traits, with the greatest reduction (51 %) occurring in grain yield. Weakly significant positive associations of biochemical and some physiological traits between the stem elongation and anthesis stages partially confirmed our first hypothesis, whereas our results relating to the second hypothesis were inconclusive. We observed genotype-dependent responses to drought stress during both stages for various measured traits. No associations of RWC, proline, or MDA with grain yield were found. However, stomatal conductance was negatively correlated with grain yield under drought stress at the anthesis stage. Certain wild wheat genotypes and landraces exhibited drought avoidance, escape, and tolerance mechanisms, which positively contributed to grain yield. We identified T. monococcum subsp. sinskajae, T. boeoticum and T. dicoccoides as the most drought-tolerant genotypes. The findings of this study provide important insight for understanding the drought adaptation traits and their use in wheat breeding programs.

Role of Dalbergia sissoo as host species in physiological and molecular adaptation of sandalwood under individual and interactive salinity and water deficit stress

The aim of present study was to investigate the viability of cultivating white sandalwood (Santalum album L.) in sub-tropical India where farmers are primarily concerned with salinity stress and water deficit as well as different genes that regulate the growth. The present research was undertaken to explore the molecular mechanism of salinity and drought tolerance in sandalwood planted with Dalbergia sissoo (selected based on prior studies) by conducting an RBD experiment under water deficit (50 %), salinity stress (ECiw ∼ 8 ds/m) and combined 50 % water deficit and saline stress (ECiw ∼ 8 ds/m). After two years of imposed treatments, leaves were collected from sandalwood to study the relative gene expression of salinity tolerance (SOS 1, NHX 1 and NHX 2), antioxidant enzymes (SOD, CAT, APX and POX), proline synthesis (P5CS and P5CR) and nitrogen metabolism (NR, NIR, GS and GDH) related genes using real-time PCR (RT-PCR). Different morpho-physiological and biochemical traits showed reduction under individual and interactive stresses except proline and Na+ content as well as anti-oxidative enzyme activities. So far, gene expression studies have not been fully validated in sandalwood under abiotic stresses. The results displayed that SOS 1, NHX 1, NHX 2, APX, POX, CAT, SOD, P5CS and P5CR genes showed maximum expression under combined salinity and water deficit stress. On the other side, genes involved in nitrogen metabolism, i.e., NR, NIR, GS and GDH showed lowest expression under individual as well as interactive water deficit and salinity stress. The current study also highlights the significance of the host D. sissoo which may be good long-term host species in terms of stress tolerance mechanism at molecular level for sandalwood production under changing environmental conditions.

Modeling Root Development of Rice (Oryza sativa L) under Varying Drought Stress

In the current era, where drought occurrences are frequent and devastating, extensive study on drought tolerance mechanisms is imperative. Root growth under water stress is a key indicator of drought tolerance. Modeling a crop's root-length under such conditions aids in predicting seminal root length (SRL) and, consequently, its tolerance level. Under consecutive stress using Poly-ethylene-glycol (PEG), root length of a landrace originating from the drought-prone area of West Bengal, India was measured through image analysis and then mathematically modulated using an equation. The highest root length under stress was predicted at 6% PEG stress which aligned with the experimental readings. On the 15th day of stress, predicted SRL values were 104.67mm and experimental values were 90.00mm. Despite some over and underestimations with a low root mean square error of 14.68 mm, the equation provides insight into root elongation trends under various stress levels, offering a basis for predicting SRL and yield capabilities under water stress for diverse crop species.

Transcriptomic Insights into Drought Survival Strategy of Sorghum bicolor (L.) Moench during Early Growth under Polyethylene Glycol-Simulated Conditions

Drought stress during sorghum emergence significantly affects seedling establishment, adversely affecting both emergence and population growth. This study investigates drought tolerance mechanisms during sorghum germination by analyzing physiological changes and transcriptomic data from two lines: W069 (drought tolerant) and W040 (drought sensitive). Under drought conditions, a phenotypic analysis revealed that W069 exhibited longer shoots and roots than W040. Additionally, physiological data indicated higher osmotic substance and lower malondialdehyde levels in W069. Using Kyoto Encyclopedia of Genes and Genome analyses, we identified three key pathways (starch and sucrose metabolism, phenylpropanoid biosynthesis, and phytohormone signaling) as pivotal in the drought response during seed germination in sorghum plants. Expression profiling revealed that most drought tolerance-related genes in the three key pathways were expressed at higher levels in the drought-tolerant cultivar W069, possibly explaining its greater stress tolerance. These findings enhance our understanding of drought-responsive gene networks in sorghum seed germination, offering potential target genes and strategies for enhancing drought tolerance in this crop.

Contrasted agronomical and physiological responses of five Coffea arabica genotypes under soil water deficit in field conditions.

Breeding programs have developed high-yielding Coffea arabica F1-hybrids as an adaptation against adverse conditions associated with climate change. However, theresponse to drought of coffee F1 hybrids has seldom been assessed. A trial was established with five C. arabica genotypes (2 pure lines: Catimor and Marsellesa and 3 F1 hybrids: Starmaya, Centroamericano and Mundo Maya) planted under the leguminous tree species Leuceana leucocephala. Coffee growth, yield and physiological responses were assessed under a rain-fed (control: CON) and a rainfall reduction treatment (RR) for 2 years. The RR treatment created a long-term rainfall deficit in a region with suboptimal temperature similar to those predicted by climate change scenarios. Moreover, the RR treatment reduced soil water content by 14% over 2 successive years of production and increased hydric stress of the three F1-hybrids (leaf water potentials averaged -0.8 MPa under RR compared with -0.4 MPa under CON). Under RR, coffee yields were reduced from 16 to 75% compared to CON. Mundo Maya F1 hybrid was the sole high-yielding genotype apable of sustaining its yield under RR conditions. Our results suggested that its significant increase in fine root density (CON = 300 and RR = 910 root.m-2) and its maintenance of photosynthetic rate (2.5 - 3.5 mmol CO2 m-2 s-1) at high evaporative demand might explain why this genotype maintained high yield under RR condition. This work highlights a possible drought tolerance mechanism in fruit bearing adult coffee trees where the plant fine root number increases to intake more water in order to preserve turgor and sustainphotosynthesis at high ETo and therefore conserves high yield in dry conditions.

The BpPP2C-BpMADS11-BpERF61 signaling confers drought tolerance in Betula platyphylla.

Plant MADS-box proteins are vital for abiotic stress tolerance, yet their mechanisms for responding to drought remain poorly understood. Here, we investigated the drought tolerance mechanism of a MADS-box protein (BpMADS11) from birch (Betula platyphylla) using immunoprecipitation, Western blotting, yeast two-hybrid, yeast one-hybrid, ChIP, RNA-seq, and dual-luciferase assays to explore post-translational modifications, protein interactions, and gene regulation. Birch plants overexpressing BpMADS11 exhibited enhanced drought tolerance, while knockout lines displayed reduced tolerance. Under drought conditions, BpMADS11 interacts with protein phosphatase 2C22 (BpPP2C22), which dephosphorylates BpMADS11. Birch plants that overexpress BpMADS11 and lack BpPP2C22 show significantly reduced drought tolerance compared with those that only overexpress BpMADS11. BpMADS11 regulates the expression of BpERF61 by binding to CArG-box in its promoter. The dephosphorylated BpMADS11 exhibits increased DNA binding ability and increased expression of BpERF61. Like BpMADS11, birch plants overexpressing BpERF61 show improved drought tolerance, while those with BpERF61 knockout exhibit decreased tolerance. BpERF61 binds to specific DNA motifs including 'CACGTG' (G-box), 'GGGCCCC', and 'TTGGAT' to regulate the genes related to drought stress. Collectively, BpMADS11 undergoes dephosphorylation through its interaction with BpPP2C22, prompting the expression of BpERF61. Subsequently, BpERF61 regulates downstream genes by binding to specific DNA motifs, thereby enhancing drought tolerance.

Integrated PacBio SMRT and Illumina sequencing uncovers transcriptional and physiological responses to drought stress in whole-plant Nitraria tangutorum.

Nitraria tangutorum Bobr., a prominent xerophytic shrub, exhibits remarkable adaptability to harsh environment and plays a significant part in preventing desertification in northwest China owing to its exceptional drought and salinity tolerance. To investigate the drought-resistant mechanism underlying N. tangutorum, we treated 8-week-old seedlings with polyethylene glycol (PEG)-6000 (20%, m/m) to induce drought stress. 27 samples from different tissues (leaves, roots and stems) of N. tangutorum at 0, 6 and 24h after drought stress treatment were sequenced using PacBio single-molecule real-time (SMRT) sequencing and Illumina RNA sequencing to obtain a comprehensive transcriptome. The PacBio SMRT sequencing generated 44,829 non-redundant transcripts and provided valuable reference gene information. In leaves, roots and stems, we identified 1162, 2024 and 232 differentially expressed genes (DEGs), respectively. The Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis revealed that plant hormone signaling and mitogen-activated protein kinase (MAPK) cascade played a pivotal role in transmitting stress signals throughout the whole N. tangutorum plant following drought stress. The interconversion of starch and sucrose, as well as the biosynthesis of amino acid and lignin, may represent adaptive strategies employed by N. tangutorum to effectively cope with drought. Transcription factor analysis showed that AP2/ERF-ERF, WRKY, bHLH, NAC and MYB families were mainly involved in the regulation of drought response genes. Furthermore, eight physiological indexes, including content of proline, hydrogen peroxide (H2O2), malondialdehyde (MDA), total amino acid and soluble sugar, and activities of three antioxidant enzymes were all investigate after PEG treatment, elucidating the drought tolerance mechanism from physiological perspective. The weighted gene co-expression network analysis (WGCNA) identified several hub genes serve as key regulator in response to drought through hormone participation, ROS cleavage, glycolysis, TF regulation in N. tangutorum. These findings enlarge genomic resources and facilitate research in the discovery of novel genes research in N. tangutorum, thereby establishing a foundation for investigating the drought resistance mechanism of xerophyte.

Physiological and Transcriptomic Characterization of Rice Genotypes under Drought Stress

Drought is a primary abiotic stress that inhibits rice (Oryza sativa L.) growth and development, and during the reproductive stage it has a negative impact on the rice seed-setting rate. This research study examined two rice lines, La-96 (drought sensitive) and La-163 (drought resistant), for drought stress treatment (with soil moisture at 20% for 7 days) and control (normal irrigation and kept soil moisture ≥40%). To elucidate the photosynthesis and molecular mechanisms underlying drought tolerance in rice, leaf photosynthetic traits and transcriptome sequencing were used to compare differences between two contrasting recombinant inbred lines (RIL) during drought and subsequent recovery at the booting stage. The rice line La-96 showed a significant decrease in seed-setting rate after being treated for seven days’ drought stress (from 86.64% to 22.75%), while La-163 was slightly affected (from 89.04% to 79.33%). The photosynthetic activities of both lines significantly decreased under the drought treatment, and these traits of La-163 recovered to a comparable level with the control after three days of rewatering. The transcriptome of both lines in three treatments (the control, drought stress, and subsequent recovery) were tested, and a total of 16,051 genes were identified, among which 10,566 genes were differentially expressed in various treatments and rice lines. Comprehensive gene expression profiles revealed that the specifically identified DEGs were involved in the ribosome synthesis and the metabolic pathway of photosynthesis, starch, and sucrose metabolism. The DEGs that are activated and respond quickly, as seen during recovery in the tolerant rice line, may play essential roles in regulating subsequent growth and development. This study uncovered the molecular genetic pathways of drought tolerance and extended our understanding of the drought tolerance mechanisms and subsequent recovery regulation in rice.

Transcriptomic and Metabolomic Profiling of Root Tissue in Drought-Tolerant and Drought-Susceptible Wheat Genotypes in Response to Water Stress.

Wheat is the most widely grown crop in the world; its production is severely disrupted by increasing water deficit. Plant roots play a crucial role in the uptake of water and perception and transduction of water deficit signals. In the past decade, the mechanisms of drought tolerance have been frequently reported; however, the transcriptome and metabolome regulatory network of root responses to water stress has not been fully understood in wheat. In this study, the global transcriptomic and metabolomics profiles were employed to investigate the mechanisms of roots responding to water stresses using the drought-tolerant (DT) and drought-susceptible (DS) wheat genotypes. The results showed that compared with the control group, wheat roots exposed to polyethylene glycol (PEG) had 25941 differentially expressed genes (DEGs) and more upregulated genes were found in DT (8610) than DS (7141). Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis showed that the DEGs of the drought-tolerant genotype were preferably enriched in the flavonoid biosynthetic process, anthocyanin biosynthesis and suberin biosynthesis. The integrated analysis of the transcriptome and metabolome showed that in DT, the KEGG pathways, including flavonoid biosynthesis and arginine and proline metabolism, were shared by differentially accumulated metabolites (DAMs) and DEGs at 6 h after treatment (HAT) and pathways including alanine, aspartate, glutamate metabolism and carbon metabolism were shared at 48 HAT, while in DS, the KEGG pathways shared by DAMs and DEGs only included arginine and proline metabolism at 6 HAT and the biosynthesis of amino acids at 48 HAT. Our results suggest that the drought-tolerant genotype may relieve the drought stress by producing more ROS scavengers, osmoprotectants, energy and larger roots. Interestingly, hormone signaling plays an important role in promoting the development of larger roots and a higher capability to absorb and transport water in drought-tolerant genotypes.

Genetic improvement of drought stress tolerance in maize, recent advancements and future research direction

Maize is an imperative crop around the globe, and it provides several essential nutrients to humans and animals. Environmental changes seriously affect growth and productivity. Drought stress is one of the most important abiotic stresses, reducing maize growth and yield and threatening global food security. For decades, breeders have been trying to improve maize's ability to counter the toxic effects of drought stress. Drought tolerance is controlled by many genes and it complicates molecular breeding. The use of conventional breeding methods limited the development of drought tolerance in maize because of the complex nature of this trait. Hence, maize breeders have shifted their focus towards improvement of drought tolerance in maize at molecular level. Different molecular tools like quantitative trait loci (QTL) mapping, genome-wide-association-studies (GWAS), transcriptome analysis, transcription factor (TFs) analysis, and CRISPR/Cas9 have played a vital role in gene’s identification and their use in molecular breeding. These genomic regions have been proven very effective, and more studies are being conducted to increase their efficiency; however, the improvement level is limited because of the complex genetic mechanism of drought tolerance. Different review articles have been published on this aspect; however, a comprehensive and updated overview of drought tolerance needs to be included. The current review highlights the role of diverse molecular techniques to improve drought tolerance in maize. This review article will enhance the interest of researchers working on the genetic improvement of maize.

Genome-wide association study provides new insight into the underlying mechanism of drought tolerance during seed germination stage in soybean

Drought is one of the major environmental issues that reduce crop yield. Seed germination is a crucial stage of plant development in all crop plants, including soybean. In soybean breeding, information about genetic mechanism of drought tolerance has great importance. However, at germination stage, there is relatively little knowledge on the genetic basis of soybean drought resistance. The objective of this work was to find the quantitative trait nucleotides (QTNs) linked to drought tolerance related three traits using a genome-wide association study (GWAS), viz., germination rate (GR), root length (RL), and whole seedling length (WSL), using germplasm population of 240 soybean PIs with 34,817 SNPs genotype data having MAF > 0.05. It was observed that heritability (H2) for GR, WSL, and RL across both environments (2020, and 2019) were high in the range of 0.76–0.99, showing that genetic factors play a vital role in drought tolerance as compared to environmental factors. A number of 23 and 27 QTNs were found to be linked to three traits using MLM and mrMLM, respectively. Three significant QTNs, qGR8-1, qWSL13-1, and qRL-8, were identified using both MLM and mrMLM methods among these QTNs. QTN8, located on chromosome 8 was consistently linked to two traits (GR and RL). The area (± 100 Kb) associated with this QTN was screened for drought tolerance based on gene annotation. Fifteen candidate genes were found by this screening. Based on the expression data, four candidate genes i.e. Glyma08g156800, Glyma08g160000, Glyma08g162700, and Glyma13g249600 were found to be linked to drought tolerance regulation in soybean. Hence, the current study provides evidence to understand the genetic constitution of drought tolerance during the germination stage and identified QTNs or genes could be utilized in molecular breeding to enhance the yield under drought stress.

Evaluation of memory drought stress effects on storage compounds seedlings of cotton (Gossypium hirsutum) and in-silico analysis of glutathione reductase

In breeding programs, stress memory in plants can develop drought stress tolerance. Memory stress, as an approach, can keep stress data by activating tolerance mechanisms. This research was conducted to evaluate some physiologically effective mechanisms in inducing memory drought stress in the seeds that were exposed to water stress three times in four treatments including rainfed, 33%, 66%, and 100% of field capacity (FC). After the production of the seeds, the third-generation seeds were placed under different irrigation treatments, seed and seedling traits, starch to carbohydrate ratio in seed, protein concentration and glutathione reductase were investigatied in a factorial format based on a randomized complete block design with three replications. Results showed that percentage of changes from the lowest to the highest value for traits including seed vigor, seed endosperm weight, seed coat weight, accelerated aging, cold test, seedling biomass and seedling length were 25, 37, 65, 65, 55, 77, 55, 65 and 79, respectively and germination uniformity was 3.9 times higher than the lowest amount. According to the deterioration percentage, seed vigor and the percentage of seed germination in cold test data, it can be reported that seed production by 100% FC was not appropriate for rainfed plots. However, considering the the appropriate results in the percentage of germination for a cold test, germination uniformity percentage, and the lowest accelerated aging seeds, seed production under the rainfed conditions with 33% FC watering can be recommended. In-silico analysis was coducted on Glutathione reductase (GR) enzymes in Gossypium hirsutum. It is clear that GR has a Redox-active site and NADPH binding, and it interacts with Glutathione S transferase (GST). So, memory drought stress through inducing physiological drought tolerance mechanisms such as starch-to-carbohydrate ratio and GR can determine the suitable pattern for seed production for rainfed and low rainfall regions in a breeding program. Our study thus illustrated that seed reprduction under 33% FC equipped cotton with the tolerance against under draught stress from the seedling stage. This process is done through activating glutathione reductase and balancing the ratio of starch to carbohydrates concentration.

Genetic, molecular and physiological crosstalk during drought tolerance in maize (Zea mays): pathways to resilient agriculture.

This review comprehensively elucidates maize drought tolerance mechanisms, vital for global food security. It highlights genetic networks, key genes, CRISPR-Cas applications, and physiological responses, guiding resilient variety development. Maize, a globally significant crop, confronts the pervasive challenge of drought stress, impacting its growth and yield significantly. Drought, an important abiotic stress, triggers a spectrum of alterations encompassing maize's morphological, biochemical, and physiological dimensions. Unraveling and understanding these mechanisms assumes paramount importance for ensuring global food security. Approaches like developing drought-tolerant varieties and harnessing genomic and molecular applications emerge as effective measures to mitigate the negative effects of drought. The multifaceted nature of drought tolerance in maize has been unfolded through complex genetic networks. Additionally, quantitative trait loci mapping and genome-wide association studies pinpoint key genes associated with drought tolerance, influencing morphophysiological traits and yield. Furthermore, transcription factors like ZmHsf28, ZmNAC20, and ZmNF-YA1 play pivotal roles in drought response through hormone signaling, stomatal regulation, and gene expression. Genes, such as ZmSAG39, ZmRAFS, and ZmBSK1, have been reported to be pivotal in enhancing drought tolerance through diverse mechanisms. Integration of CRISPR-Cas9 technology, targeting genes like gl2 and ZmHDT103, emerges as crucial for precise genetic enhancement, highlighting its role in safeguarding global food security amid pervasive drought challenges. Thus, decoding the genetic and molecular underpinnings of drought tolerance in maize sheds light on its resilience and paves the way for cultivating robust and climate-smart varieties, thus safeguarding global food security amid climate challenges. This comprehensive review covers quantitative trait loci mapping, genome-wide association studies, key genes and functions, CRISPR-Cas applications, transcription factors, physiological responses, signaling pathways, offering a nuanced understanding of intricate mechanisms involved in maize drought tolerance.

Inter-subspecies diversity of maize to drought stress with physio-biochemical, enzymatic and molecular responses.

Drought is the most significant factor limiting maize production, given that maize is a crop with a high water demand. Therefore, studies investigating the mechanisms underlying the drought tolerance of maize are of great importance. There are no studies comparing drought tolerance among economically important subspecies of maize. This study aimed to reveal the differences between the physio-biochemical, enzymatic, and molecular mechanisms of drought tolerance in dent (Zea mays indentata), popcorn (Zea mays everta), and sugar (Zea mays saccharata) maize under control (no-stress), moderate, and severe drought stress. Three distinct irrigation regimes were employed to assess the impact of varying levels of drought stress on maize plants at the V14 growth stage. These included normal irrigation (80% field capacity), moderate drought (50% field capacity), and severe drought (30% field capacity). All plants were grown under controlled conditions. The following parameters were analyzed: leaf relative water content (RWC), loss of turgidity (LOT), proline (PRO) and soluble protein (SPR) contents, membrane durability index (MDI), malondialdehyde (MDA), and hydrogen peroxide (H2O2) content, the antioxidant enzyme activities of superoxide dismutase (SOD), ascorbate peroxidase (APX), and catalase (CAT). Additionally, the expression of heat shock proteins (HSPs) was examined at the transcriptional and translational levels. The effects of severe drought were more pronounced in sugar maize, which had a relatively high loss of RWC and turgor, membrane damage, enzyme activities, and HSP90 gene expression. Dent maize, which is capable of maintaining its RWC and turgor in both moderate and severe droughts, and employs its defense mechanism effectively by maintaining antioxidant enzyme activities at a certain level despite less MDA and H2O2 accumulation, exhibited relatively high drought tolerance. Despite the high levels of MDA and H2O2 in popcorn maize, the up-regulation of antioxidant enzyme activities and HSP70 gene and protein expression indicated that the drought coping mechanism is activated. In particular, the positive correlation of HSP70 with PRO and HSP90 with enzyme activities is a significant result for studies examining the relationships between HSPs and other stress response systems. The discrepancies between the transcriptional and translational findings provide an opportunity for more comprehensive investigations into the role of HSPs in stress conditions.