Mechanisms Of Drought Tolerance Research Articles

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.

Morphological, Physiological, and Molecular Stomatal Responses in Local Watermelon Landraces as Drought Tolerance Mechanisms

Drought-tolerant plants have become a convenient model to study the mechanisms underlying drought tolerance in order to improve susceptible domesticated relatives. Various studies have shown that local landraces possess superior qualities that help them survive in harsh environmental conditions. One of the key mechanisms that helps with tolerance in crops is timely stomatal regulation. In this study, the physiological, morphological, and molecular stomatal responses in three drought-tolerant landraces (Clm-01–03) and hybrid (Clm-04) watermelons were evaluated under drought stress. The watermelon plants were grown under a water deficit (complete withholding of water) and non-stress conditions. The highest SPAD values were recorded for the Clm-03 and Clm-02 (50 ± 3) watermelon genotypes, and the lowest for Clm-04 (27 ± 0.37), showing this genotype’s tolerance and ability to maintain its systems during drought stress. Fluorescence parameters also gave important clues to the tolerant genotypes of Clm-02 and Clm-03 under drought stress, while the domesticated genotype showed a slow response to fluorescence parameters, which could lead to damage to the photosynthesis apparatus. During the drought period, the wild watermelon was found to have a limited stomatal opening as the drought progressed, and on day 9, it had the smallest opening of 23.1 ± 1.2 µm compared to any other genotype; most importantly, upon re-watering, it showed more rapid recovery than any other genotype. This was also expressed by mRNA quantification of stomatal aperture TFs, with an eight-fold increase in Cla004380 TFs recorded for wild watermelon. All of these mechanisms have been attributed to the tolerance mechanisms of the drought-tolerant watermelon genotype. This study provides important insight into the stomatal responses of probable tolerant watermelon accessions and suggests that improving the stomatal aperture of susceptible domesticated species would also improve their tolerance.

Transcriptome and Metabolome Analyses Reflect the Molecular Mechanism of Drought Tolerance in Sweet Potato

Sweet potato (Ipomoea batatas (L.) Lam.) is one of the most widely cultivated crops in the world, with outstanding stress tolerance, but drought stress can lead to a significant decrease in its yield. To reveal the response mechanism of sweet potato to drought stress, an integrated physiological, transcriptome and metabolome investigations were conducted in the leaves of two sweet potato varieties, drought-tolerant zhenghong23 (Z23) and a more sensitive variety, jinong432 (J432). The results for the physiological indexes of drought showed that the peroxidase (POD) and superoxide dismutase (SOD) activities of Z23 were 3.68 and 1.21 times higher than those of J432 under severe drought, while Z23 had a higher antioxidant capacity. Transcriptome and metabolome analysis showed the importance of the amino acid metabolism, respiratory metabolism, and antioxidant systems in drought tolerance. In Z23, amino acids such as asparagine participated in energy production during drought by providing substrates for the citrate cycle (TCA cycle) and glycolysis (EMP). A stronger respiratory metabolism ability could better maintain the energy supply level under drought stress. Drought stress also activated the expression of the genes encoding to antioxidant enzymes and the biosynthesis of flavonoids such as rutin, resulting in improved tolerance to drought. This study provides new insights into the molecular mechanisms of drought tolerance in sweet potato.

Effect of drought stress on natural rubber biosynthesis and quality in Taraxacum kok-saghyz roots.

Taraxacum kok-saghyz (TKS) is a potential source of natural rubber (NR) that can be grown in temperate regions with limited water availability. However, the effect of drought stress on NR production and properties in TKS isn't well studied. This study examined how different levels of drought stress (30, 60 and 90%) influenced the NR content, molecular weight (Mw), glass transition temperature (Tg), gene expression, and biochemical parameters in TKS roots. The results showed that drought stress didn't significantly change the NR content, but increased the Mw and the expression of CPT and SRPP genes, which are involved in NR biosynthesis. The NR from TKS roots (TNR) had a high Mw of 994,000 g/mol and a low Tg of below -60°C under normal irrigation, indicating its suitability for industrial applications. Drought stress also triggered the accumulation of proline, H2O2, MDA, and antioxidant enzymes (CAT, APX, GPX) in TKS roots significantly, indicating a drought tolerance mechanism. These findings suggest that TKS can produce high-quality NR under drought stress conditions and provide a sustainable alternative to conventional NR sources.

Physiological Characteristic Changes and Transcriptome Analysis of Maize (Zea mays L.) Roots under Drought Stress.

Water deficit is a key limiting factor for limiting yield in maize (Zea mays L.). It is crucial to elucidate the molecular regulatory networks of stress tolerance for genetic enhancement of drought tolerance. The mechanism of drought tolerance of maize was explored by comparing physiological and transcriptomic data under normal conditions and drought treatment at polyethylene glycol- (PEG-) induced drought stress (5%, 10%, 15%, and 20%) in the root during the seedling stage. The content of saccharide, SOD, CAT, and MDA showed an upward trend, proteins showed a downward trend, and the levels of POD first showed an upward trend and then decreased. Compared with the control group, a total of 597, 2748, 6588, and 5410 differentially expressed genes were found at 5%, 10%, 15%, and 20% PEG, respectively, and 354 common DEGs were identified in these comparisons. Some differentially expressed genes were remarkably enriched in the MAPK signaling pathway and plant hormone signal transduction. The 50 transcription factors (TFs) divided into 15 categories were screened from the 354 common DEGs during drought stress. Auxin response factor 10 (ARF10), auxin-responsive protein IAA9 (IAA9), auxin response factor 14 (ARF14), auxin-responsive protein IAA1 (IAA1), auxin-responsive protein IAA27 (IAA27), and 1 ethylene response sensor 2 (ERS2) were upregulated. The two TFs, including bHLH 35 and bHLH 96, involved in the MAPK signal pathway and plant hormones pathway, are significantly upregulated in 5%, 10%, 15%, and 20% PEG stress groups. The present study provides greater insight into the fundamental transcriptome reprogramming of grain crops under drought.

Unravelling mechanisms of CaO nanoparticle-induced drought tolerance in Brassica napus: an analysis of metabolite and nutrient profiling

Nanotechnology has been widely used in agriculture to improve plant growth and stress tolerance.

Morphological and physiological adaptation of a desert shrub, Encelia farinosa, under drought stress

Water scarcity in arid and semi-arid regions affects ecosystem development. Therefore, elucidation of the mechanisms by which plant species in a given region respond to drought conditions may allow us to improve global vegetation. Encelia species are drought-tolerant and an important component of shrub communities in the arid and semi-arid regions of southern California, U.S.A.; these species are widely used for vegetation restoration in the region. This study aimed to investigate the morphological, and physiological responses in E. farinosa in relation to changes in soil properties under drought conditions. Plants were subjected to two levels of soil water regimes, drought and well-watered conditions (5% and 12% of gravimetric water content, respectively). After 3 months, above-ground biomass, basal diameter, leaf area, leaf and root relative water content, and root length were measured. The shoot:root ratio in dry mass and specific leaf area (SLA) were calculated. We also analyzed leaf and soil nutrients, including total C, N, and available P. In the drought treatment, E. farinosa showed significantly lower above-ground biomass, stem diameter, and shoot and root relative water content. Also, the drought treatment resulted in significantly lower leaf areas, while the SLA and root length were significantly higher. Leaf total C and N were higher in the drought treatment while leaf P was not affected by soil water content. The reduction in plant leaf area, root elongation and the increase in SLA under drought are known as drought avoidance strategies of plants, suggesting that E. farinosa hampers water loss by morphological regulations. Additionally, higher leaf content of C and N seems to be important for metabolic drought adaptation. Further research on osmotic adjustment and antioxidant defense systems will clarify the detailed drought tolerance mechanisms of E. farinosa in relation to C and N accumulation under drought conditions.

Regimes hídricos nas respostas morfofisiológicas e bioquímicas de Croton blanchetianus (Euphorbiaceae)

ABSTRACT Plant species occurring in the Caatinga biome, when subjected to different water fluctuations, may have their morphophysiological and metabolic performance altered. Depending on the level of stress, the production of quality seedlings is affected. Therefore, the objective of this study was to evaluate the responses to different water availability levels in the morphophysiological and biochemical development of Croton blanchetianus Baill. The experiment was carried out in a greenhouse, evaluating four water regimes: 25%, 50%, 75% and 100% of pot capacity, and conducted in a randomized block design, with a total 5 blocks. The variables analyzed were: branch height and branch diameter; leaf area, number of leaves, root volume; root dry mass, shoot dry mass, total dry mass and root/shoot ratio; relative water content, proline, total soluble proteins, malondialdehyde, hydrogen peroxide, and photo synthetic pigments (chlorophyll ɑ, chlorophyll b, and carotenoids). The species Croton blanchetianus Baill. shows drought tolerance mechanisms, demonstrated by the reductions of growth, leaf area, dry mass of seedlings and photo synthetic pigments. It adjusts osmotically with increments in the production of proline, which acts in osmoprotection when there is water deficit, and in the production of proteins under the lower and higher water regime. The species has full development of seedlings under water regimes between 75% and 80% and adapts to different water fluctuations.

Antioxidant Defense System and Physiological Insights to Drought Stress in Urtica dioica L.

Urtica dioicais an endemic perennial plant of rocky habitat of Western Black Sea region of Turkey. To understand drought responses and tolerance mechanism of Seseli resinosum Freyn & Sint., relative water content (RWC), chlorophyll fluorescence, proline accumulation, lipid peroxidation (TBARS), hydrogen peroxide (H2O2) content and changes in antioxidant enzymes were assayed in polyethylene glycol (PEG) 6000 (5, 10 and 15%) induced drought stress in the present study. Leaf RWC maintained unchanged, while chlorophyll fluorescence reduced with high level of PEG (15%). Additionally, H2O2 and proline accumulation were determined with the increase of PEG application, but no increase in the amount of TBARS was determined. Moreover, the increment in H2O2 content under drought was accompanied by increased in glutathione reductase, catalase and superoxide dismutase activities. On the other hand, PEG-induced drought stress caused a reduction in peroxidase and ascorbate peroxidase activities. These results suggest that endemic Urtica dioica plant have an efficient drought tolerance, as displayed by enhanced antioxidant enzyme activities with maintaining water status under drought conditions. In this study, important information about physiological and antioxidative responses of endemic Urtica dioica was revealed for the first time.

Fighting Drought: A Mini Review with Special Reference to Tropical Palms

Drought stress is the most important environmental stress which affects negatively on plant growth and productivity. With the climate change and the scarcity of water, drought conditions have become frequent and prominent, affecting the agricultural production worldwide. Therefore, breeding crops for drought tolerance has gained significant attention at present. To cope with drought, plants possess different mechanisms and understanding their biological significance would enable the utilization of these mechanisms in crop improvement for drought tolerance. Therefore, in the current review an effort has been made to compile the information related to drought tolerance mechanisms and drought resistant/tolerant crop improvement with special reference to tropical palm tree species.

Türk Ekmeklik Buğday (T. aestivum L.) Çeşidi Gerek 79'da Kuraklığa-Duyarlı Genlerin mRNA Farklılık Gösterim Analizi İle Tanımlanması

Wheat is one of the most important cereal crops in the world. Many parts of the world depend on wheat as a source of food and animal feed. Drought stress negatively affects its development and greatly reduce its production. Drought response is a complex genetic mechanism involving multiple genes, transcription factors, miRNAs, hormones, proteins, co-factors, ions, and metabolites. The understanding of genetic basis of the drought tolerance mechanisms is very important for genetic improvement of this trait in wheat. Wheat is also an important cereal crop in Turkey. In this study, it is aimed to identify drought stress-regulated genes in bread wheat (Triticum aestivum cv. Gerek 79) and gene expression profiling using mRNA differential display (mRNA DD) was performed for seedling leaves of control and drought-stressed plants (62.4% of RWC). The comparative profiling study showed a total of 20 differentially-expressed cDNA bands and 10 of them were cloned and sequenced. The inserts having poor quality reads were eliminated. The nucleotide sequences of the remaining two cDNAs named G1 and G2 were subjected to similarity analysis. G1 and G2 showed a high degree of homology to mRNA sequence of purple acid phosphatase and glycosyltransferase family 92 protein-like sequence of Triticum aestivum and some other plants, respectively. Purple acid phosphatases have been shown to be involved in plant responses to abiotic and biotic stresses. Similarly, the role of glycosyltransferases on thermotolerance has been reported in rice besides their functions in cellular homeostasis and detoxification pathways in plants. These reports and our findings have laid a foundation for further investigation of G1 and G2 cDNA clones. The investigation of differential expression of these gene fragments corresponding to purple acid phosphatase and glycosyltransferase family 92 protein-like sequence under drought conditions at the RNA level is ongoing. Further characterization of these genes could be important in understanding the functions of these gene/s in drought response.

Exploring the interplay of phytohormones and polyamines in drought-stressed Cress (<i>Lepidium sativum</i> L.) leaves

The study investigated prolonged drought stress effects on phytohormone and polyamine levels in cress (Lepidium sativum L.) leaves, elucidating plant responses to harsh environments. Phytohormones, 12-oxophytodienoic acid (OPDA), Jasmonic acid (JA), Jasmonyl-Isoleucine (JA-Ile), Abscisic acid (ABA), and salicylic acid (SA) increased, especially ABA that rose consistently. Indole-3-acetic acid (IAA) responded akin to ABA and SA. Cytokinins such as zeatin (ZT) and isopentenyl adenine (iP) diversified drought tolerance, ZT fell sharply, and iP remained stable. Gibberellic acid (GA3) declined, while brassinolide (BL) surged with prolonged drought. Polyamines reduced, indicating sensitivity to severe drought. Findings uncovered intricate regulatory mechanisms for plant adaptation to water scarcity. Interaction of OPDA, JA, JA-Ile, ABA, SA, IAA, ZT, iP, GA3, BL, and polyamines contributes to drought coping and physiological balance. Insights into cress leaf response and drought tolerance mechanisms contribute significantly to plant drought adaptation understanding.

Exploring mechanisms of drought-tolerance and adaptation of selected sesame mutant lines

Sesame (Sesamum indicum L.) is an important oilseed crop, but its productivity and quality are often compromised by drought stress. Developing drought-resistant sesame varieties is thus crucial for its sustainable cultivation. In this study, we conducted a comprehensive investigation of morphoanatomical and physiochemical mechanisms underlying drought tolerance in selected sesame mutants. The drought-tolerant mutants ‘ML2-37’ and ‘ML2-72’ were compared to the susceptible mutant ‘US1-2’ and the parental cultivar ‘ML13’ under controlled greenhouse conditions. Our results showed that the tolerant mutants exhibited superior performance in response to drought stress. We identified specific adaptation mechanisms, including accumulation of proline, glycine, and cuticular wax, which contribute to maintaining optimal water status. Additionally, the tolerant mutants showed a significant reduction in the number and diameter of the xylem vessels, even under severe stress. These results open up good perspectives for the development of drought-resistant sesame varieties, thus offering a promising solution to improve agricultural productivity in regions affected by increasing water scarcity in the actual context of climate change. The selection indices proposed in this study provide practical tools to identify and develop sesame germplasm and cultivars adapted to drought stress conditions. This work constitutes a significant contribution to research on drought tolerance in sesame and offers promising prospects for sustainable agriculture in the context of global climate change.

Comprehensive expression profiling analysis to investigate salt and drought responding genes in wild barley (Hordeum spontaneum L.)

Drought and salinity are among the most affecting abiotic stress factors that limit the productivity in economically important plants. Understanding drought and salt tolerance mechanism is pivotal for developing drought and salt tolerant crop cultivars. Here, we monitored the changes in gene expression profiles of leaf and root tissues of two wild barley (Hordeum spontaneum L.) accessions after treatment with salt and drought stresses. We identified a total of 641 DEGs across 24 conditions (2 accessions, 2 stress conditions, 2 tissues and 3 time-points). Interestingly, there was a relatively little overlap between the leaf and the root stress responsive gene expression patterns, suggesting that different stress associated processes might be operating in these tissues during stress adaptation. In hierarchical clustering, the genes with distinct expression patterns were nearly half found in Cluster 1 and Cluster 9 and DEGs found in Cluster 9 were significantly enriched for metabolic processes and organic substance metabolic process. Gene ontology (GO) annotations of biological process of salt and drought analysis identified genes in categories including, catabolic processes, oxidation–reduction and organic substance metabolic process. Molecular function analyses significantly detected transcripts associated with oxidoreductase activity and nucleotide binding. Overall, our results revealed a number of candidate genes and plant processes associated with stress tolerance in wild barley. Determination of responsive genes will shed light on other barley studies aiming to elucidate molecular mechanism of drought or salt tolerance.

Genomic assembly, characterization, and quantification of DICER-like gene family in Okra plants under dehydration conditions.

Okra is a plant farmed for its pods, leaves, and stems all of which are edible. It is famous for its ability to tolerate long desiccation periods. It belongs to the Malvaceae family and is a sister species to hibiscus, cotton, and cacao plants. In the current study, okra plants were used as a model to sequence, assemble, and analyze the evolutionary and functional characteristics of the Dicer-like protein gene family (DCL) based on DNAseq and qPCR techniques. Four Dicer-like (DCL) single-copy genes of the okra plant Abelmoschus esculentus (L.) Moench (AeDCL) were successfully assembled. The lengths of the AeDCL copies were 8,494, 5,214, 4,731, and 9,329 bp. The detected exons in these samples ranged from a single exon in AeDCL3 to 24 exons in AeDCL4. AeDCLs had five functional domains of two DEAD-like helicase superfamilies, N and C; one Dicer domain; one ribonuclease III domain (a and b); and one double-stranded RNA-binding domain. The PAZ domain was completely annotated only for AeDCL1 and AeDCL3. All AeDCLs were up-regulated under drought conditions, with leaves showing more extensive fold changes than roots. The study focused on a comprehensive genome-wide identification and analysis of the DCL gene family in naturally drought-tolerant okra plants, an orphan crop that can be used as a model for further genomic and transcriptomic studies on drought-tolerance mechanisms in plants.

Physiological response and drought resistance evaluation of Gleditsia sinensis seedlings under drought-rehydration state

G. sinensis is a crucial tree species in China, possessing important economic and ecological value, and having a wide geographical distribution. G. sinensis seedlings is highly vulnerable to the drought-rehydration-drought cycle during their growth, and there is a lack of quantitative and systematic research on the physiological mechanisms of drought resistance and rehydration in G. sinensis. There is also a lack of good drought-resistant families and reliable methods for evaluating drought resistance, which severely hinders the selection and promotion of drought-resistant G. sinensis families and the industry's development. Therefore, this study selection 58 families seedlings of G. sinensis to drought stress and rehydration using an artificial simulated water control method in potted seedlings. The aim was to compare the effects of different levels of drought and rehydration on the growth and physiological indices of seedlings from different families. Identification of drought-resistant families and dependable drought related indices and techniques, the explanation of divergence in drought stress effects on various drought-resistant seedlings and the mechanisms underpinning growth and physiological responses, and the provision of theoretical reference for G. sinensis drought-resistant variety selection and cultivation. The Drought Resistance Index (DRI) served as the primary indicator, supplemented by growth, leaf morphology, and photosynthetic physiological indicators, to thoroughly assess and identify five distinct drought tolerant taxa while also selecting five representative families. Soluble protein (SP), proline (Pro), and malondialdehyde (MDA) contents, as well as the activities of catalase (CAT), peroxidase (POD) and superoxide dismutase (SOD) in seedlings from the five families, increased as the degree of drought intensified. The highest values were appeared during periods of severe drought, and gradually decreased after subsequent rehydration. Principal component analysis (PCA) revealed MDA and soluble sugars (SS) as the primary predictors of drought and rehydration response in G. sinensis seedlings respectively. Changes in osmoregulatory substance content and increased antioxidant enzyme activity may be crucial for responding to drought tolerance mechanisms. Leaf morphological indicators, seedling height, soil plant analysis development (SPAD) value, photosynthetic indicators, and MDA are dependable parameters for assessing the drought tolerance of G. sinensis seedlings. When assessing the drought-resistance of seedlings using physiological indicators such as photosynthesis, a comprehensive analysis should incorporate multiple indicators and methods. This evaluation approach could serve as a reference for screening exceptional drought-resistant families of G. sinensis.