Mechanisms Of Drought Tolerance Research Articles

Investigating the morpho-physiological and biochemical traits of chia (Salvia hispanica) to drought stress

ABSTRACT Chia (Salvia hispanica L.) cultivation in dry regions like Morocco requires understanding its drought tolerance for successful projects amidst climate change threats. In this context, a study was conducted to assess the effect of severe drought stress on chia seedlings. Under drought stress conditions, growth traits of the shoot part have been significantly decreased, while the root part did not change significantly compared to control conditions. A significant reduction in chlorophylls and carotenoids was noted in stressed chi seedlings. In comparison with control conditions, the predawn leaf water potential and stomatal conductance significantly decreased by about 81.4% and 35.3%, respectively, in stressed chia seedlings, without detecting any significant change in the relative water content. Drought-stressed chia seedlings exhibited significant accumulation of epicuticular wax (approximately 57.7%) on leaves compared to control seedlings. In addition, chia seedlings exhibited osmotic adjustment under conditions of severe drought stress, characterised by a substantial accumulation of proline (fourfold increase) and proteins (85.6%) compared to control conditions. Significant correlations have been established between some traits that interfere with plant responses to drought stress. Nonetheless, thorough examinations of chia's drought tolerance mechanisms are crucial for informed strategies for its cultivation in arid and marginal regions.

Review on blueberry drought tolerance from the perspective of cultivar improvement.

Blueberry (Vaccinium spp.) is an increasingly popular fruit around the world for their attractive taste, appearance, and most importantly their many health benefits. Global blueberry production was valued at $2.31 billion with the United States alone producing $1.02 billion of cultivated blueberries in 2021. The sustainability of blueberry production is increasingly threatened by more frequent and extreme drought events caused by climate change. Blueberry is especially prone to adverse effects from drought events due to their superficial root system and lack of root hairs, which limit blueberry's ability to intake water and nutrients from the soil especially under drought stress conditions. The goal of this paper is to review previous studies on blueberry drought tolerance focusing on physiological, biochemical, and molecular drought tolerance mechanisms, as well as genetic variability present in cultivated blueberries. We also discuss limitations of previous studies and potential directions for future efforts to develop drought-tolerant blueberry cultivars. Our review showed that the following areas are lacking in blueberry drought tolerance research: studies of root and fruit traits related to drought tolerance, large-scale cultivar screening, efforts to understand the genetic architecture of drought tolerance, tools for molecular-assisted drought tolerance improvement, and high-throughput phenotyping capability for efficient cultivar screening. Future research should be devoted to following areas: (1) drought tolerance evaluation to include a broader range of traits, such as root architecture and fruit-related performance under drought stress, to establish stronger association between physiological and molecular signals with drought tolerance mechanisms; (2) large-scale drought tolerance screening across diverse blueberry germplasm to uncover various drought tolerance mechanisms and valuable genetic resources; (3) high-throughput phenotyping tools for drought-related traits to enhance the efficiency and affordability of drought phenotyping; (4) identification of genetic architecture of drought tolerance using various mapping technologies and transcriptome analysis; (5) tools for molecular-assisted breeding for drought tolerance, such as marker-assisted selection and genomic selection, and (6) investigation of the interactions between drought and other stresses such as heat to develop stress resilient genotypes.

The ZmbHLH47-ZmSnRK2.9 Module Promotes Drought Tolerance in Maize.

Drought stress globally poses a significant threat to maize (Zea mays L.) productivity and the underlying molecular mechanisms of drought tolerance remain elusive. In this study, we characterized ZmbHLH47, a basic helix-loop-helix (bHLH) transcription factor, as a positive regulator of drought tolerance in maize. ZmbHLH47 expression was notably induced by both drought stress and abscisic acid (ABA). Transgenic plants overexpressing ZmbHLH47 displayed elevated drought tolerance and ABA responsiveness, while the zmbhlh47 mutant exhibited increased drought sensitivity and reduced ABA sensitivity. Mechanistically, it was revealed that ZmbHLH47 could directly bind to the promoter of ZmSnRK2.9 gene, a member of the subgroup III SnRK2 kinases, activating its expression. Furthermore, ZmSnRK2.9-overexpressing plants exhibited enhanced ABA sensitivity and drought tolerance, whereas the zmsnrk2.9 mutant displayed a decreased sensitivity to both. Notably, overexpressing ZmbHLH47 in the zmsnrk2.9 mutant closely resembled the zmsnrk2.9 mutant, indicating the importance of the ZmbHLH47-ZmSnRK2.9 module in ABA response and drought tolerance. These findings provided valuable insights and a potential genetic resource for enhancing the environmental adaptability of maize.

Gene expression analysis of drought tolerance and cuticular wax biosynthesis in diploid and tetraploid induced wallflowers

Whole-genome doubling leads to cell reprogramming, upregulation of stress genes, and establishment of new pathways of drought stress responses in plants. This study investigated the molecular mechanisms of drought tolerance and cuticular wax characteristics in diploid and tetraploid-induced Erysimum cheiri. According to real-time PCR analysis, tetraploid induced wallflowers exhibited increased expression of several genes encoding transcription factors (TFs), including AREB1 and AREB3; the stress response genes RD29A and ERD1 under drought stress conditions. Furthermore, two cuticular wax biosynthetic pathway genes, CER1 and SHN1, were upregulated in tetraploid plants under drought conditions. Leaf morphological studies revealed that tetraploid leaves were covered with unique cuticular wax crystalloids, which produced a white fluffy appearance, while the diploid leaves were green and smooth. The greater content of epicuticular wax in tetraploid leaves than in diploid leaves can explain the decrease in cuticle permeability as well as the decrease in water loss and improvement in drought tolerance in wallflowers. GC‒MS analysis revealed that the wax components included alkanes, alcohols, aldehydes, and fatty acids. The most abundant wax compound in this plant was alkanes (50%), the most predominant of which was C29. The relative abundance of these compounds increased significantly in tetraploid plants under drought stress conditions. These findings revealed that tetraploid-induced wallflowers presented upregulation of multiple drought-related and wax biosynthesis genes; therefore, polyploidization has proved useful for improving plant drought tolerance.

Autophagy receptor ZmNBR1 promotes the autophagic degradation of ZmBRI1a and enhances drought tolerance in maize.

Drought stress is a crucial environmental factor that limits plant growth, development, and productivity. Autophagy of misfolded proteins can help alleviate the damage caused in plants experiencing drought. However, the mechanism of autophagy-mediated drought tolerance in plants remains largely unknown. Here, we cloned the gene for a maize (Zea mays) selective autophagy receptor, NEXT TO BRCA1 GENE 1 (ZmNBR1), and identified its role in the response to drought stress. We observed that drought stress increased the accumulation of autophagosomes. RNA sequencing and reverse transcription-quantitative polymerase chain reaction showed that ZmNBR1 is markedly induced by drought stress. ZmNBR1 overexpression enhanced drought tolerance, while its knockdown reduced drought tolerance in maize. Our results established that ZmNBR1 mediates the increase in autophagosomes and autophagic activity under drought stress. ZmNBR1 also affects the expression of genes related to autophagy under drought stress. Moreover, we determined that BRASSINOSTEROID INSENSITIVE 1A (ZmBRI1a), a brassinosteroid receptor of the BRI1-like family, interacts with ZmNBR1. Phenotype analysis showed that ZmBRI1a negatively regulates drought tolerance in maize, and genetic analysis indicated that ZmNBR1 acts upstream of ZmBRI1a in regulating drought tolerance. Furthermore, ZmNBR1 facilitates the autophagic degradation of ZmBRI1a under drought stress. Taken together, our results reveal that ZmNBR1 regulates the expression of autophagy-related genes, thereby increasing autophagic activity and promoting the autophagic degradation of ZmBRI1a under drought stress, thus enhancing drought tolerance in maize. These findings provide new insights into the autophagy degradation of brassinosteroid signaling components by the autophagy receptor NBR1 under drought stress.

Meta-Quantitative Trait Loci Analysis and Candidate Gene Mining for Drought Tolerance-Associated Traits in Maize (Zea mays L.).

Drought is one of the major abiotic stresses with a severe negative impact on maize production globally. Understanding the genetic architecture of drought tolerance in maize is a crucial step towards the breeding of drought-tolerant varieties and a targeted exploitation of genetic resources. In this study, 511 quantitative trait loci (QTL) related to grain yield components, flowering time, and plant morphology under drought conditions, as well as drought tolerance index were collected from 27 published studies and then projected on the IBM2 2008 Neighbors reference map for meta-analysis. In total, 83 meta-QTL (MQTL) associated with drought tolerance in maize were identified, of which 20 were determined as core MQTL. The average confidence interval of MQTL was strongly reduced compared to that of the previously published QTL. Nearly half of the MQTL were confirmed by co-localized marker-trait associations from genome-wide association studies. Based on the alignment of rice proteins related to drought tolerance, 63 orthologous genes were identified near the maize MQTL. Furthermore, 583 candidate genes were identified within the 20 core MQTL regions and maize-rice homologous genes. Based on KEGG analysis of candidate genes, plant hormone signaling pathways were found to be significantly enriched. The signaling pathways can have direct or indirect effects on drought tolerance and also interact with other pathways. In conclusion, this study provides novel insights into the genetic and molecular mechanisms of drought tolerance in maize towards a more targeted improvement of this important trait in breeding.

A Case Study from the Overexpression of OsTZF5, Encoding a CCCH Tandem Zinc Finger Protein, in Rice Plants Across Nineteen Yield Trials

BackgroundDevelopment of transgenic rice overexpressing transcription factors involved in drought response has been previously reported to confer drought tolerance and therefore represents a means of crop improvement. We transformed lowland rice IR64 with OsTZF5, encoding a CCCH-tandem zinc finger protein, under the control of the rice LIP9 stress-inducible promoter and compared the drought response of transgenic lines and nulls to IR64 in successive screenhouse paddy and field trials up to the T6 generation.ResultsCompared to the well-watered conditions, the level of drought stress across experiments varied from a minimum of − 25 to − 75 kPa at a soil depth of 30 cm which reduced biomass by 30–55% and grain yield by 1–92%, presenting a range of drought severities. OsTZF5 transgenic lines showed high yield advantage under drought over IR64 in early generations, which was related to shorter time to flowering, lower shoot biomass and higher harvest index. However, the increases in values for yield and related traits in the transgenics became smaller over successive generations despite continued detection of drought-induced transgene expression as conferred by the LIP9 promoter. The decreased advantage of the transgenics over generations tended to coincide with increased levels of homozygosity. Background cleaning of the transgenic lines as well as introgression of the transgene into an IR64 line containing major-effect drought yield QTLs, which were evaluated starting at the BC3F1 and BC2F3 generation, respectively, did not result in consistently increased yield under drought as compared to the respective checks.ConclusionsAlthough we cannot conclusively explain the genetic factors behind the loss of yield advantage of the transgenics under drought across generations, our results help in distinguishing among potential drought tolerance mechanisms related to effectiveness of the transgenics, since early flowering and harvest index most closely reflected the levels of yield advantage in the transgenics across generations while reduced biomass did not.

A reference-grade genome of the xerophyte Ammopiptanthus mongolicus sheds light on its evolution history in legumes and drought-tolerance mechanisms

Plants that grow in extreme environments represent unique sources of stress-resistance genes and mechanisms. Ammopiptanthus mongolicus (Leguminosae) is a xerophytic evergreen broadleaf shrub native to semi-arid and desert regions; however, its drought-tolerance mechanisms remain poorly understood. Here, we report the assembly of a reference-grade genome for A. mongolicus, describe its evolutionary history within the legume family, and examine its drought-tolerance mechanisms. The assembled genome is 843.07 Mb in length, with 98.7% of the sequences successfully anchored to the nine chromosomes of A. mongolicus. The genome is predicted to contain 47 611 protein-coding genes, and 70.71% of the genome is composed of repetitive sequences; these are dominated by transposable elements, particularly long-terminal-repeat retrotransposons. Evolutionary analyses revealed two whole-genome duplication (WGD) events at 130 and 58 million years ago (mya) that are shared by the genus Ammopiptanthus and other legumes, but no species-specific WGDs were found within this genus. Ancestral genome reconstruction revealed that the A. mongolicus genome has undergone fewer rearrangements than other genomes in the legume family, confirming its status as a “relict plant”. Transcriptomic analyses demonstrated that genes involved in cuticular wax biosynthesis and transport are highly expressed, both under normal conditions and in response to polyethylene glycol-induced dehydration. Significant induction of genes related to ethylene biosynthesis and signaling was also observed in leaves under dehydration stress, suggesting that enhanced ethylene response and formation of thick waxy cuticles are two major mechanisms of drought tolerance in A. mongolicus. Ectopic expression of AmERF2, an ethylene response factor unique to A. mongolicus, can markedly increase the drought tolerance of transgenic Arabidopsis thaliana plants, demonstrating the potential for application of A. mongolicus genes in crop improvement.

Effect of drought stress on the expression pattern of genes involved in ABA biosynthesis in Desi-type chickpea (Cicer arietinum L.).

The behavior of Abscisic acid (ABA) as a stress phytohormone may be involved in mechanisms leading to tolerance and survival in adverse environmental conditions such as drought stress. Here, we evaluated ABA-mediated responses at physio-biochemical and molecular levels in drought-stressed seedlings of two different Desi-type chickpea genotypes (10 as a tolerant genotype and 247 as a sensitive one). Under drought stress, two chickpea genotypes showed a decrease in their relative water content (RWC), and the intense decrease was related to the sensitive genotype (73.9%) in severe stress. Hydrogen peroxide (H2O2) and malondialdehyde (MDA) concomitant with the severity of stress increased in genotypes and the higher increase was in the sensitive genotype (5.8-fold and 3.43-fold, respectively). In the tolerant genotype, the enhanced accumulation of total phenolic content (1.75-fold) and radical scavenging action, based on 1,1-diphenyl-2-picrylhydrazyl test (DPPH), (1.69-fold) were simultaneous with ABA accumulation (1.53-fold). In the tolerant genotype, transcriptional analysis presented upregulation of Zeaxanthin epoxidase (ZEP) (1.35-fold), 9-cis-epoxycarotenoid dioxygenase (NCED) (5.16-fold), and Abscisic aldehyde oxidase (AAO) (1.52-fold compared to control conditions) genes in severe stress in comparison with mild stress. The sensitive genotype had a declining trend in total chlorophyll (up to 70%) and carotenoid contents (36%). The main conclusion to be drawn from this investigation is that ABA with its regulatory effects can affect drought tolerance mechanisms to alleviate adverse effects of unsatisfactory environmental conditions. In this paper, we tried to indicate that drought stress induces overexpression of genes triggering ABA-mediated drought responses simultaneously in two genotypes while more increment expression was related to the tolerant genotype. At first thought, it seems that the tolerant genotype compared to the sensitive genotype has a genetically inherent ability to cope with and drop adverse effects of drought stress through over-accumulation of ABA as drought.

Transcriptomic and Metabolomic Analyses Reveal the Response to Short-Term Drought Stress in Bread Wheat (Triticum aestivum L.)

Drought stress, a major abiotic stress, significantly affects wheat (Triticum aestivum L.) production globally. To identify genes and metabolic pathways crucial for responding to short-term drought stress, we conducted transcriptomic and metabolomic analyses of winter wheat cultivar Jimai 418 at four developmental stages: jointing (GS31), booting (GS45), anthesis (GS65), and 8 days after anthesis (DAA8). Transcriptomic analysis identified 14,232 differentially expressed genes (DEGs) under drought stress compared to the control. Specifically, 1387, 4573, 7380, and 892 DEGs were identified at the four developmental stages, respectively. Enriched pathways associated with these DEGs included plant hormone signal transduction, mitogen-activated protein kinase (MAPK) signaling, galactose metabolism, and starch and sucrose metabolism. Totals of 222, 633, 358, and 38 differentially accumulated metabolites (DAMs) were identified at the four stages, respectively. Correlation analysis of both datasets revealed DEGs and DAMs associated with plant hormone signal transduction, arginine and proline metabolism, ABC transporters, and amino acid biosynthesis. These findings offer significant insights into Jimai 418’s molecular response to short-term drought stress. The identified DEGs, DAMs, and enriched pathways contribute to our understanding of wheat drought tolerance. This research will facilitate further investigations into drought tolerance mechanisms and guide the breeding of wheat varieties with enhanced drought resistance.

Developing Drought Tolerance in Field Crops towards Current Century: An Integrated Bio-Molecular Approach

Drought stresses are foremost threat to plant growth, productivity as well as sustainability towards agriculture through worldwide. Some of the classical breeding approaches have been attempted to develop crop performance towards stress without significant success and so therefore, recently genetic engineering in crop plants is recognized as an alternative strategy to generate drought tolerant crop plants. Various integrated biological approaches have been undertaken to overcome such drought hurdles in achieving the full potentiality of the plant growth and production as well as improving the drought tolerance in different field crops. Some approaches are commonly used to identify genes related to drought tolerance and genes to be identified which are involved in processes known to be critical for drought tolerance; whose expression is regulated by drought stress and that consists in the identification of drought tolerance determinants based on functionality. Plant researchers have developed several spurts of biological novel ‘Omics’ technologies viz. genomics, transcriptomics, proteomics and metabolomics etc to engineer plant stress tolerance. In this review, an attempt has been made to summarize the current information based on recent literature towards recent understanding as well as latest advancement related to the adverse effect of plant under drought and their adaptations or tolerance towards such abiotic stress with a focus on the identification of drought tolerance mechanisms by soil management practices, crop establishment and exogenous application of growth regulators by regulating an appropriate level of water due to osmotic adjustment and stomatal performance etc at an integrated biological level of approach.

Isobaric Tags for Relative and Absolute Quantitation-Based Proteomics Analysis Revealed Proteins Involved in Drought Response during the Germination Stage in Faba Bean.

The faba bean, a significant cool-season edible legume crop, is susceptible to drought during the germination stage. Research regarding the genetic regulation of drought tolerance throughout this stage in the faba bean is limited. The differentially expressed proteins (DEPs) in faba beans between the drought-tolerant variety C105 and the drought-sensitive variant E1 during seed germination were identified in this work, accomplished through isobaric tags for relative and absolute quantitation (iTRAQ) analysis. A total of 3827 proteins were identified in the two varieties of germinating seeds. Compared to those of variety E1, an increase in 108 DEPs and a decrease in 61 DEPs were observed in variety C105 under drought. Conversely, in the control group, variety C105 showed 108 significantly upregulated DEPs and 55 significantly downregulated DEPs. GO and KEGG analyses showed that the DEPs associated with glutathione metabolism and protein processing demonstrated significant increases in response to drought stress. Protein-protein interaction (PPI) analysis unveiled three closely connected functional modules of protein translation, DNA replication, and post-translational modification, originating from 22 DEPs derived from the germination period of two varieties under drought stress. To verify the proteomic function, we selected three differentially expressed protein coding genes, which were overexpressed or silenced in tobacco, thereby enhancing the drought resistance of tobacco. This was accompanied via altered levels of superoxide dismutase or peroxidase in transgenic plants under drought stress. The possible mechanism for drought tolerance in germinating seeds of faba bean involves increasing protein translation, decreasing DNA replication, and modifying chromatin. These findings offer invaluable insights into the reaction mechanism in response to drought stress in faba beans. The identified DEPs could be utilized in faba bean breeding initiatives to manage drought.

Physiological Regulation of Photosynthetic-Related Indices, Antioxidant Defense, and Proline Anabolism on Drought Tolerance of Wild Soybean (Glycine soja L.)

Wild soybean (Glycine soja L.), drought-tolerant cultivar Tiefeng 31 (Glycine max L.), and drought-sensitive cultivar Fendou 93 (Glycine max L.) were used as materials to investigate the drought tolerance mechanism after 72 h 2.5 M PEG 8000 (osmotic potential −0.54 MPa)-simulated drought stress at the seedling stage. The results indicated that the leaves of the G. soja did not wilt under drought stress. However, both the drought-tolerant and drought-sensitive cultivated soybean cultivars experienced varying degrees of leaf wilt. Notably, the drought-sensitive cultivated soybean cultivars exhibited severe leaf wilt after the drought stress. Drought stress was determined to have a significant impact on the dry matter of the above-ground part of the drought-sensitive cultivar Fendou 93, followed by the drought-tolerant cultivar Tiefeng 31, with the lowest reduction observed in G. soja. Furthermore, the presence of drought stress resulted in the closure of leaf stomata. G. soja exhibited the highest proportion of stomatal opening per unit area, followed by the drought-tolerant cultivar Tiefeng 31, while the drought-sensitive cultivar Fendou 93 displayed the lowest percentage. Photosynthesis-related indexes, including photosynthetic rate, intercellular CO2, transpiration rate, and stomatal conductance, decreased in Fendou 93 and Tiefeng 31 after drought stress, but increased in G. soja. In terms of the antioxidant scavenging system, lower accumulation of malondialdehyde (MDA) was observed in G. soja and Tiefeng 31, along with higher activities of superoxide dismutase (SOD, EC 1.15.1.1) and catalase (CAT, EC 1.11.1.6) to counteract excess reactive oxygen species and maintain cell membrane integrity. In contrast, the drought-sensitive cultivar Fendou 93 had higher MDA content and higher activities of ascorbate peroxidase (APX, EC 1.11.1.11) and peroxidase (POD, 1.11.1.7). G. soja and Tiefeng 31 also exhibited less accumulation of osmolytes, including soluble sugar, soluble protein, and free proline content. The activities of δ-OAT, ProDH, and P5CS, key enzymes in proline anabolism, showed an initial increase under drought stress, followed by a decrease, and then an increase again at the end of drought stress in G. soja. Before drought stress, Tiefeng 31 had higher activities of ProDH and P5CS, which decreased with prolonged drought stress. Fendou 93 experienced an increase in the activities of δ-OAT, ProDH, and P5CS under drought stress. The δ-OAT gene expression levels were up-regulated in all three germplasms. The expression levels of the P5CS gene in Fendou 93 and Tiefeng 31 were down-regulated, while G. soja showed no significant change. The expression of the P5CR gene and ProDH gene was down-regulated in Fendou 93 and Tiefeng 31, but up-regulated in G. soja. This indicates that proline content is regulated at both the transcription and translation levels.

Differential drought tolerance among dichondra (Dichondra repens) genotypes in relation to alterations in chlorophyll metabolism, osmotic adjustment, and accumulation of organic metabolites.

Dichondra (Dichondra repens) is an important ground cover plant for landscaping and establishment of green space, but adaptive mechanism of drought tolerance is not well understood in this species. This study was conducted to compare differential response to drought stress among three genotypes (Dr5, Duliujiang, and Dr29) based on integrated physiological, ultrastructural, and metabolic assays. Results showed that drought significantly inhibited photosynthesis, accelerated lipids peroxidation, and also disrupted water balance and cellular metabolism in dichondra plants. Dr5 showed better photochemical efficiency of photosystem II and water homeostasis, less oxidative damage, and more stable chlorophyll metabolism than Duliujinag or Dr29 in response to drought stress. In addition, Dr5 accumulated more amino acids, organic acids, and other metabolites, which was good for maintaining better antioxidant capacity, osmotic homeostasis, and energy metabolism under drought stress. Drought tolerance of Duliujiang was lower than Dr5, but better than Dr29, which could be positively correlated with accumulations of sucrose, maltitol, aconitic acid, isocitric acid, and shikimic acid due to critical roles of these metabolites in osmotic adjustment and metabolic homeostasis. Current findings provide insights into understanding of underlying mechanism of metabolic regulation in dichondra species. Dr5 could be used as an important drought-tolerant resource for cultivation and water-saving breeding.

Physiological and Molecular Modulations to Drought Stress in the Brassica Species.

Climate change, particularly drought stress, significantly impacts plant growth and development, necessitating the development of resilient crops. This study investigated physiological and molecular modulations to drought stress between diploid parent species and their polyploid progeny in the Brassica species. While no significant phenotypic differences were observed among the six species, drought stress reduced growth parameters by 2.4% and increased oxidative stress markers by 1.4-fold. Drought also triggered the expression of genes related to stress responses and led to the accumulation of specific metabolites. We also conducted the first study of perfluorooctane sulfonic acid (PFOS) levels in leaves as a drought indicator. Lower levels of PFOS accumulation were linked to plants taking in less water under drought conditions. Both diploid and polyploid species responded to drought stress similarly, but there was a wide range of variation in their responses. In particular, responses were less variable in polyploid species than in diploid species. This suggests that their additional genomic components acquired through polyploidy may improve their flexibility to modulate stress responses. Despite the hybrid vigor common in polyploid species, Brassica polyploids demonstrated intermediate responses to drought stress. Overall, this study lays the framework for future omics-level research, including transcriptome and proteomic studies, to deepen our understanding of drought tolerance mechanisms in Brassica species.

Transcriptome analysis reveals regulatory mechanisms of different drought-tolerant Gleditsia sinensis seedlings under drought stress

BackgroundGleditsia sinensis is a significant tree species from both ecological and economic perspectives. However, its growth is hampered by temporary droughts during the seedling stage, thereby impeding the development of the G. sinensis industry. Drought stress and rehydration of semi-annual potted seedlings using an artificial simulated water control method. RNA sequencing (RNA-seq) analyses were conducted on leaves collected from highly resistant (HR) and highly susceptible (HS) seedling families at five different stages during the process of drought stress and rehydration to investigate their gene expression patterns.ResultsThe differentially expressed genes (DEGs) were predominantly enriched in pathways related to “chloroplast” (GO:0009507), “photosynthesis” (GO:0015979), “plant hormone signal transduction” (map04075), “flavonoid biosynthesis” (map00941), “stress response”, “response to reactive oxygen species (ROS)” (GO:0000302), “signal transduction” (GO:0007165) in G. sinensis HR and HS families exposed to mild and severe drought stress. Additionally, the pathways related to “plant hormone signal transduction” (map04075), and osmoregulation were also enriched. The difference in drought tolerance between the two families of G. sinensis may be associated with “transmembrane transporter activity” (GO:0022857), “stress response”, “hormones and signal transduction” (GO:0007165), “cutin, suberine and wax biosynthesis” (map00073), “ribosome” (map03010), “photosynthesis” (map00195), “sugar metabolism”, and others. An enrichment analysis of DEGs under severe drought stress suggests that the drought tolerance of both families may be related to “water-soluble vitamin metabolic process” (GO:0006767), “photosynthesis” (map00195), “plant hormone signal transduction” (map04075), “starch and sucrose metabolism” (map00500), and “galactose metabolism” (map00052). Osmoregulation-related genes such as delta-1-pyrroline-5-carboxylate synthase (P5CS), Amino acid permease (AAP), Amino acid permease 2 (AAP2) and Trehalose-phosphate synthase (TPS), as well as the antioxidant enzyme L-ascorbate peroxidase 6 (APX6), may be significant genes involved in drought tolerance in G. sinensis. Five genes were selected randomly to validate the RNA-seq results using quantitative real-time PCR (RT-qPCR) and they indicated that the transcriptome data were reliable.ConclusionsThe study presents information on the molecular regulation of the drought tolerance mechanism in G. sinensis and provides a reference for further research on the molecular mechanisms involved in drought tolerance breeding of G. sinensis.

Back to the future for drought tolerance.

Global agriculture faces increasing pressure to produce more food with fewer resources. Drought, exacerbated by climate change, is a major agricultural constraint costing the industry an estimated US$80 billion per year in lost production. Wild relatives of domesticated crops, including wheat (Triticum spp.) and barley (Hordeum vulgare L.), are an underutilized source of drought tolerance genes. However, managing their undesirable characteristics, assessing drought responses, and selecting lines with heritable traits remains a significant challenge. Here, we propose a novel strategy of using multi-trait selection criteria based on high-throughput spectral images to facilitate the assessment and selection challenge. The importance of measuring plant capacity for sustained carbon fixation under drought stress is explored, and an image-based transpiration efficiency (iTE) index obtained via a combination of hyperspectral and thermal imaging, is proposed. Incorporating iTEalong with other drought-related variables in selection criteria will allow the identification of accessions with diverse tolerance mechanisms. A comprehensive approach that merges high-throughput phenotyping and de novo domestication is proposed for developing drought-tolerant prebreeding material and providing breeders with access to gene pools containing unexplored drought tolerance mechanisms.

Onion (Allium cepa L.) and Drought: Current Situation and Perspectives.

Onions (Allium cepa L.) are the second most commonly produced and consumed vegetable worldwide due to their economic, nutritional, and medicinal benefits. However, drought hinders vegetative growth, lowers yields and bulb quality, reduces photosynthetic activity, and alters the onion plant's metabolism. This review provides a summary of global research on the impact of drought on onions. It specifically seeks to shed light on aspects that remain unclear and generate research avenues. Relevant scientific articles were sourced from the AGORA database, Web of Science (WoS), and search engines such as Google Scholar, Scopus, MEDLINE/PubMed, and SCImago to achieve this objective. A total of 117 scientific articles and documents related to onion and drought were critically examined. The review revealed agromorphological, physiological, biochemical, and genomic studies depicting factors that contribute to drought tolerance in onion genotypes. However, there was little research on the physiological, biochemical, and genetic characteristics of drought tolerance in onions, which need to be deepened to establish its adaptation mechanisms. Understanding the mechanisms of onion response to water stress will contribute to fast-tracking the development of drought-tolerant genotypes and optimize onion production. Future research should be more focused on investigating onion drought tolerance mechanisms and structural and functional genomics and identifying genes responsible for onion drought tolerance.

Alteration in physio-chemical properties and gene expression pattern of snapmelon (Cucumis melo var. momordica) genotypes against drought stress

AbstractLack of water at limiting levels results in drought stress, which may have an impact on the various stages of a crop's life cycle. Four different genotypes of snapmelon (Cucumis melo L. var. momordica) responded differently to 0, 7 and 21 d of simulated drought stress. Information was collected on a range of morpho-physiological, biochemical and molecular characteristics. Each genotype had longer roots, though BAM-VR-312 had the longest roots overall. As the severity of the drought grew, the net photosynthetic rate (Pn) and stomatal conductance (Gs) dropped. In BAM-VR-312, a smaller decline in relative water content (RWC) was recorded, despite the fact that drought stress caused a significant fall in RWC. BAM-VR-312 had smaller accumulations of electrolyte leakage, hydrogen peroxide, phenol and malondialdehyde, although proline content was greater. A decrease in photosynthetic pigments was noted, though BAM-VR-312 had the least reduction. Antioxidant enzyme activity increased in BAM-VR-312, as evidenced by records of ascorbate peroxidase, catalase, guaiacol peroxidase, glutathione reductase and superoxide dismutase. Similarly, expression level of their respective genes was recorded highest in BAM-VR-312. Overall, the study clearly identified distinct genotype based on morpho-physiological, biochemical and molecular properties under drought stress and revealed that the genotype BAM-VR-312 had more efficient drought tolerance mechanisms than the other genotypes under the drought stress condition.

Monitoring Drought Tolerance Mechanisms of Sorghum and Maize Under Unevenly Distributed Precipitation

The study examines the morpho-physiological differences in leaf characteristics between two species of C4 plants: sorghum and maize. The research was conducted in field conditions where plants were rainfed. Both species different varieties were cultivated at two distinct sites that exhibited variations in soil texture and drought stress incidence according to the vegetation condition index (VCI). Samples were collected during various growth stages to analyze the relative water content (RWC), proline levels, and stomatal density. Sorghum plants displayed higher RWC, proline levels, and stomatal density than maize plants. In sorghum, the biochemical traits, such as the proline content, may play a more critical role in withstanding water-limited conditions than in maize in our experiment. Under the same water restriction period, sorghum showed higher RWC levels. Sorghum plants reduced stomatal density under more water-limited conditions, which proves its plasticity. Additionally, early maturation played a crucial role in both species. The early sorghum variety KWS Kallisto and maize variety Walterinio KWS had a more stable yield at both sites. Nevertheless, the highest yields were found in the later varieties, KWS Hannibal and KWS Inteligens. The higher proline levels and the relative water content are drought-tolerant mechanisms and may be used to indicate drought intensity in field conditions. Our findings spotlight the influence of genetic diversity and genotype-environment interactions in determining crop responses to drought stress, providing valuable information for future breeding programs to enhance drought tolerance in crops.