Xerophytic Research Articles

GhLCYε-3 characterized as a lycopene cyclase gene responding to drought stress in cotton

Drought stress significantly affects crop productivity. Carotenoids are essential photosynthetic pigment for plants, bacteria, and algae, with signaling and antioxidant functions. Lutein is a crucial branch product in the carotenoid synthesis pathway, which effectively improves the stress tolerance of higher plants. lycopene cyclase, a central enzyme for lutein synthesis, holds great significance in regulating lutein production. This research establishes a correlation between lutein content and stress resistance by measuring the drought resistance and lutein content of various cotton materials. To identify which crucial genes are associated with lutein, the lycopene cyclase family (LCYs) was analyzed. The research found that LCYs form a highly conserved family divided into two subfamilies, LCY-ε (lycopene ε-cyclase) and LCY-β (lycopene β-cyclase). Most members of the LCY family contain photoresponsive elements and abscisic acid elements. qRT-PCR demonstrates showed that most genes responded positively to drought stress, and GhLCYε-3 was expressed significantly differently under drought stress. Virus-induced gene silencing (VIGS) assay showed that the content of GhLCYε-3 was significantly increased with MDA and PRO, and the contents of chlorophyll and lutein were significantly decreased in pYL156 plants. The decrease in GhLCYε-3 expression is speculated to lead to reduced lutein content in vivo, resulting in the accumulation of reactive oxygen species (ROS) and decreased drought tolerance. This research enriched the understanding of LCY gene family and lutein function, and provided a new reference for cotton planting in arid areas. SynopsisLycopene cyclase plays an important role in enhancing the ability of scavenging ROS and drought resistance of plants.

Exploring the Genetic Basis of Drought Tolerance in Alhagi camelorum: A Comprehensive Transcriptome Study of Osmotic Stress Adaptations

Alhagi camelorum, a desert shrub known for its impressive drought tolerance, exhibits notable resilience under arid conditions. However, the underlying mechanisms driving its drought resistance remain largely unexplored. This study aims to investigate these mechanisms by exposing A. camelorum to osmotic stress using varying polyethylene glycol (PEG) concentrations (1%, 5%, 10%) in a controlled laboratory setting. Growth analysis revealed significant inhibition and phenotypic changes with increasing PEG levels. Transcriptomic analysis, including differentially expressed gene identification, GO enrichment analysis, and hierarchical cluster analysis of genes in roots and shoots, identified key pathways associated with drought adaptation, such as ABA-activated signaling, cell wall biogenesis, photosynthesis, and secondary metabolite biosynthesis. Notably, some genes involved in these pathways exhibited tissue-specific expression patterns and showed PEG concentration-dependent regulation. Key findings include the dose-dependent (R2 > 0.8) upregulation of a proline-rich protein (Asp01G030840) and a BURP domain-containing protein (Asp02G039780), as well as critical genes involved in cell wall biogenesis (encoding Pectinesterase inhibitor domain-containing and Fasciclin-like arabinogalactan protein), and secondary metabolite biosynthesis (encoding enzymes for terpenoid and flavonoid biosynthesis). The regulation of these genes is likely influenced by phytohormones such as ABA and other stress-related hormones, along with significant transcription factors like ABI4, TALE, MYB61, GRAS, and ERF. These insights lay the groundwork for further research into the functional roles of these genes, their regulatory networks, and their potential applications in enhancing drought resistance in desert plants and agricultural crops.

A high-throughput approach for quantifying turgor loss point in grapevine

Quantifying drought tolerance in crops is critical for agriculture management under environmental change, and drought response traits in grape vine have long been the focus of viticultural research. Turgor loss point (πtlp) is gaining attention as an indicator of drought tolerance in plants, though estimating πtlp often requires the construction and analysis of pressure-volume (P-V) curves which are very time consuming. While P-V curves remain a valuable tool for assessing πtlp and related traits, there is considerable interest in developing high-throughput methods for rapidly estimating πtlp, especially in the context of crop screening. We tested the ability of a dewpoint hygrometer to quantify variation in πtlp across and within 12 clones of grape vine (Vitis vinifera subsp. vinifera) and one wild relative (Vitis riparia), and compared these results to those derived from P-V curves. At the leaf-level, methodology explained only 4–5% of the variation in πtlp while clone/species identity accounted for 39% of the variation, indicating that both methods are sensitive to detecting intraspecific πtlp variation in grape vine. Also at the leaf level, πtlp measured using a dewpoint hygrometer approximated πtlp values (r2 = 0.254) and conserved πtlp rankings from P-V curves (Spearman’s ρ = 0.459). While the leaf-level datasets differed statistically from one another (paired t-test p = 0.01), average difference in πtlp for a given pair of leaves was small (0.1 ± 0.2 MPa (s.d.)). At the species/clone level, estimates of πtlp measured by the two methods were also statistically correlated (r2 = 0.304), did not deviate statistically from a 1:1 relationship, and conserved πtlp rankings across clones (Spearman’s ρ = 0.692). The dewpoint hygrometer (taking ∼ 10–15 min on average per measurement) captures fine-scale intraspecific variation in πtlp, with results that approximate those from P-V curves (taking 2–3 h on average per measurement). The dewpoint hygrometer represents a viable method for rapidly estimating intraspecific variation in πtlp, and potentially greatly increasing replication when estimating this drought tolerance trait in grape vine and other crops.

Root hair developmental regulators orchestrate drought triggered microbiome changes and the interaction with beneficial Rhizobiaceae

Drought is one of the most serious abiotic stresses, and emerging evidence suggest plant microbiome affects plant drought tolerance. However, there is a lack of genetic evidence regarding whether and how plants orchestrate the dynamic assembly of the microbiome upon drought. By utilizing mutants with enhanced or decreased root hair densities, we find that root hair regulators also affect drought induced root microbiome changes. Rhizobiaceae is a key biomarker taxa affected by root hair related mutants. We isolated and sequenced 1479 root associated microbes, and confirmed that several Rhizobium strains presented stress-alleviating activities. Metagenome, root transcriptome and root metabolome studies further reveal the multi-omic changes upon drought stress. We knocked out an ornithine cyclodeaminase (ocd) gene in Rhizobium sp. 4F10, which significantly dampens its stress alleviating ability. Our genetic and integrated multi-omics studies confirm the involvement of host genetic effects in reshaping a stress-alleviating root microbiome during drought, and provide mechanistic insights into Rhizobiaceae mediated abiotic stress protection.

Altering endogenous cytokinin content by GmCKX13 as a strategy to develop drought-tolerant plants

Climate-resilient crops are essential to meet the growing food demands of an ever-increasing world population. The phytohormone cytokinins (CKs) have been well established to regulate plant adaptation to drought. Previously, we reported that GmCKX13, encoding a CK oxidase/dehydrogenase in soybean (Glycince max), was differentially expressed under drought. Here, we further characterized its in planta function to assess if GmCKX13 could be a candidate gene to develop drought-tolerant crops. Transgenic Arabidopsis 35S:GmCKX13 plants ectopically and constitutively expressing GmCKX13 using the 35S promoter had an increase in root length, while showing a reduction in shoot height and biomass. CK contents were reduced in 35S:GmCKX13 plants, coupled with the reduced expression of all AtCKX genes and increased expression of all Arabidopsis isopentenyl transferase (AtIPT) genes, except AtIPT2 and AtIPT9 that are responsible for the production of cis-zeatin-type CKs. The 35S:GmCKX13 plants showed improved tolerance to drought and more sensitivity to the treatment with exogenous abscisic acid (ABA). Under the control of the drought-responsive promoter RD29A, the transgenic RD29A:GmCKX13 Arabidopsis plants had a similar phenotype as that of the wild-type (WT) plants under normal conditions. Under dehydration, we found a significant increase in the expression of the transgene coupled with a higher leaf relative water content in RD29A:GmCKX13 plants when compared with WT plants. In consistence with this finding, the RD29A:GmCKX13 plants exhibited higher survival rates and 30 % higher seed yield than the WT plants under drought conditions. Taken together, our results demonstrated that GmCKX13 is an excellent gene for developing drought-tolerant crops by altering endogenous CK levels and ABA responsiveness when being driven by a drought-responsive promoter.

Light Drought Stress Positively Influenced Root Morphological and Endogenous Hormones in Pinus massoniana Seedlings Inoculated with Suillus luteus

Aims An ectomycorrhizal fungus (ECMF) may enhance plant drought resistance. However, there is limited information regarding the effects of ECMFs on drought resistance in Pinus massoniana Lamb., a native species representing an afforestation pioneer tree in subtropical regions of China. Methods In this study, a pot experiment was conducted to determine the effects of ECMF Suillus luteus inoculation on the root morphology and endogenous hormones of P. massoniana, including roots, leaves, and stems, under various water treatment conditions. Four water levels (regular, light, moderate, and severe drought) and three inoculations (inoculated Suillus luteus, numbered S12 and S13, and non-ECMF-inoculated) were compared using a factorial design. Results Under drought stress, P. massoniana seedlings inoculated with S12 and S13 had significantly increased root morphology development (p < 0.05). Light drought positively influenced root development, resulting in a more than twofold increase in root length and root surface area compared to non-inoculated seedlings. Concentrations of gibberellic acid (GA), zeatin riboside (ZR), and indole-3-acetic acid (IAA) in roots, stems, and leaves of inoculated S12 and S13 plants were elevated, whereas abscisic acid (ABA) concentrations were significantly lower, compared to non-inoculated seedlings. The ABA concentrations in the roots of S12 and S13 inoculated seedlings under light drought stress were 1.5 times lower than those in non-inoculated controls. Moreover, root development was positively correlated with plant total GA, IAA, and ZR but negatively correlated with ABA. ConclusionsS. luteus can promote the root growth and development of P. massoniana seedlings, notably by regulating the balance in the concentration of endogenous hormones, thus improving the drought resistance of P. massoniana seedlings.

Cadmium uptake and transport in vegetables near a zinc–lead mine: Novel insights from Cd isotope fractionation

In this study, Cd isotope analysis was conducted on drought-tolerant (cowpea and sesame) and less drought-tolerant vegetables (water spinach, green pepper, and mung bean) to elucidate the mechanisms underlying Cd uptake and transport. Cd isotopes in plants were identical to or lighter than those in the available pool and exhibited negative fractionation from roots to straws (Δ114/110Cd = −0.22 ‰ to −0.17 ‰) in drought-tolerant vegetables, whereas contrasting results were obtained for less drought-tolerant vegetables (Δ114/110Cd = −0.050 ‰ to 0.39 ‰). Positive Cd isotope fractionation from straws to fruits in drought-tolerant vegetables (Δ114/110Cd = 0.33 ‰ ± 0.03 ‰ and 0.10 ‰ ± 0.03 ‰, respectively) was observed, whereas negligible or negative fractionation was found in less drought-tolerant vegetables (Δ114/110Cd = 0.01 ‰ ± 0.04 ‰ and −0.34 ‰ ± 0.02 ‰, respectively). The vast secretion of organic acids might have led to positive available pool-to-roots and negative roots-to-straws isotope fractionation in drought-tolerant vegetables. In contrast, preferential xylem transport resulted in negative straws-to-fruits isotope fractionation in less drought-tolerant vegetables. This study demonstrated that Cd isotope fractionation in the soil-plant system is associated with plant drought tolerance, and drought-tolerant and less-tolerant plants developed a distinct Cd detoxification mechanism, corresponding to a reversed fractionation of Cd isotopes.

Coupling of leaf economic and hydraulic strategy spectra facilitates desert restoration: A 70-year chronosequence study of Korshinks peashrub (Caragana korshinskii)

Vegetation restoration is a pivotal component in the restoration and management of desert. But shifts in the ecological strategies of established plant species, and how that may impact desert restoration, are both largely unknown. Here, we studied changes to the leaf economic strategy spectra (ESS), hydraulic strategy spectra (HSS) and soil strategy spectra (SSS) of the legume Caragana korshinskii in 3-, 5-, 10-, 20-, 30-, 40-, 50-, 60-, and 70-year restoration in Baijitan area of the MuUs desert, and investigated the relationship of these spectrums for enhancing desert restoration. The results showed that, over the years, both spectra changed significantly. The economic strategy of this plant shifted from a ‘fast investment-return’ to a more conservative ‘slow investment-return’ strategy. Concurrently, its hydraulic strategy transitioned from an isohydric to an anisohydric behavior. Along the restoration chronosequence, the resource acquisition strategy spectra declined in its effect and importance while the carbon investment in leaf construction increased. In this way, the drought tolerance and embolic resistance of plants were enhanced over time. We identify a coupling relationship between the economic and hydraulic strategy spectra. Furthermore, changed in the ESS and HSS influence the SSS over restoration years, ultimately favoring ecological restoration. This research provides foundational data for optimizing the cultivation management of Caragana korshinskii in terms of restoration years, enhancing ecosystem stability and productivity, and protecting and restoring the ecological environment.

Genome-wide identification of shaker K+ channel gene family in sugar beet (Beta vulgaris L.) and function of BvSKOR in response to salt and drought stresses

Potassium (K+) is the most abundant cation in plants, which is absorbed by roots and distributed throughout the plants and within plant cells, and is involved in various cellular processes. Shaker K+ channel plays crucial roles in the absorption and distribution of K+ and in the response to abiotic stress in plants. Herein, a total of six shaker K+ channel genes, BvKAT1, BvKAT3, BvAKT1, BvAKT2, BvAKT5, and BvSKOR, were identified in the genome of sugar beet (Beta vulgaris L.). The coding domain sequences (CDS) of these genes ranged from 2232 to 2739 bp, and protein lengths were varied from 743 to 912 aa. The shaker K+ channel genes contained hormone-related and light responsiveness cis-acting regulatory elements. The phylogenetic analysis showed that BvSKOR was highly conserved and contained six transmembrane structures. The expression patterns of BvSKOR under salt and osmotic stress were analyzed by qRT-PCR, and found that the expression level of BvSKOR under low concentration salt and osmotic stress at short period of treatment were significantly higher than that of the control group. The function of BvSKOR was further verified in tobacco (Nicotiana tabacum), and the results showed that under salt and osmotic stress, the roots of transgenic plants were significantly stronger than those of wild type (WT) plants, and the relative water content (RWC), chlorophyll, proline, soluble sugar, soluble proteins contents and antioxidant enzyme activity were significantly higher than those of WT plants. These results indicated that overexpression of BvSKOR can significantly enhance the salt and drought tolerance in transgenic tobacco plants. This study could provide theoretical support and genetic resources for genetic improvement of crops stress resistance.

MYB30-INTERACTING E3 LIGASE 1 regulates LONELY GUY 5-mediated cytokinin metabolism to promote drought tolerance in cotton

Abstract Ubiquitination plays important roles in modulating the abiotic stress tolerance of plants. Drought seriously restricts agricultural production, but how ubiquitination participates in regulating drought tolerance remains largely unknown. Here, we identified a drought-inducible gene, MYB30-INTERACTING E3 LIGASE 1 (GhMIEL1), which encodes a RING E3 ubiquitin ligase in cotton (Gossypium hirsutum). GhMIEL1 was strongly induced by polyethylene glycol (PEG-6000) and the phytohormone abscisic acid. Overexpression and knockdown of GhMIEL1 in cotton substantially enhanced and reduced drought tolerance, respectively. GhMIEL1 interacted with the MYB transcription factor GhMYB66 and could ubiquitinate and degrade it in vitro. GhMYB66 directly bound to the LONELY GUY 5 (GhLOG5) promoter, a gene encoding cytokinin riboside 5′-monophosphate phosphoribohydrolase, to repress its transcription. Overexpression of GhMIEL1 and silencing of GhMYB66 altered the homeostasis of cytokinin of plant roots, increased total root length and number of root tips, and enhanced plant drought tolerance. Conversely, silencing GhLOG5 decreased total root length and number of root tips and reduced plant drought tolerance. Our studies reveal that the GhMIEL1-GhMYB66-GhLOG5 module positively regulates drought tolerance in cotton, which deepens our understanding of plant ubiquitination-mediated drought tolerance and provides insights for improving drought tolerance.

Meta-analysis of SnRK2 gene overexpression in response to drought and salt stress.

SNF1-RELATED KINASE 2 (SnRK2) plays a crucial role in plants' stress response. Although studies have reported that the overexpression of several SnRK2 family members in different plants leads to improved stress tolerance, it is difficult to elucidate the mechanisms by which SnRK2s regulate stress tolerance due to the variability of experimental variables in these studies. Therefore, we used meta-analysis to comprehensively analyze 22 parameters that can reflect drought tolerance and salinity tolerance in SnRK2s-transformed plants and to explore the effects that different experimental variables between studies have on the relevant plant parameters. The results showed that the overexpression of SnRK2s mainly improved plants' drought and salinity tolerance by reducing their osmotic stress and oxidative damage, improving photosynthesis and other biochemical and physiological processes. Out of the 22 physiological parameters, 17 and 19 were significantly affected by drought and salt stress, respectively, and 10 indicators were also significantly changed under non-stress conditions. Under salt stress, the cell membrane permeability among these parameters shows the most significant changes, increasing by 506.57% in SnRK2-overexpressing plants compared to wild type (WT). Therefore, although plants overexpressing SnRK2s respond positively to both drought and salt stress, they demonstrated greater tolerance to salt stress. In addition, among the detected regulatory variables, donor-acceptor type, promoter type, stress type, experimental medium, and duration all affected the extent of SnRK2s overexpression and affected the physiological characteristics of the transgenic plants. Also, different stress conditions (salt, drought stress) led to different degrees of transformation. These studies provide new research directions for studying crop stress tolerance and help to better explore the functions played by SnRK2s in external plant stresses.

Comparative transcriptome analysis of B. oleracea L. var. italica and B. macrocarpa Guss. genotypes under drought stress: de novo vs reference genome assembly

Drought stress influences plant growth and development affecting some physiological processes during the growing cycle. The improvement of the drought stress resistance of the plant will allow the reduction of the water requirements of the crops, representing the new frontier for agriculture, as consequence of the ongoing climatic changes. The individuation of genetic features useful for enhancing the reduction of water use and the plant drought resistance will be one of the key strategy for providing enough food for the foreseen increment of the global population. Nowadays, the cultivars used for modern agriculture show a narrow genetic diversity due to the domestication process carried out of each crop, resulting with a less adaptation to the environmental conditions affected by both antropic activities and the climatic change in act. Among the several grown species, Brassica oleracea L. (n = 9) crops are particularly vulnerable to the adverse effects of water deficiency. Transcriptomic analysis is a powerful tool that allows researchers to identify genes and pathways, that are activated or repressed in response to each specific stress, elucidating the complex regulatory networks that underlie the correspondent response. To individuate the differentially expressed genes we compared two drought-sensitive B. oleracea L. var. botritis x italica Sicilian landraces and two drought-tolerant B. macrocarpa Guss populations grown in ordinary irrigation regimes and in water deficit conditions. Their transcriptome was obtained by a RNAseq approach. The individuated sensible and tolerant drought stress genotypes showed significant difference for H2O2 content, leaf area and SPAD index (Soil Plant Analysis Development). For better identify crucial genes and pathways associated with drought stress response of both the sensible and tolerant genotypes a thorough evaluation of both de novo assembly and reference B. oleracea var. italica genome-based assembly was conducted. The comparison of the transcriptomes allowed to identify the crucial genes and pathways associated with tolerance to drought stress in Brassica oleracea L. crops. As main results, we individuated one gene coding transcription factor showing opposite behavior in the sensitive and tolerant signatures. The adoption of two transcriptome assembly methods provided a more comprehensive dataset, enabling an unbiased interpretation of the outcomes.

Metarhizium anisopliae (MetA1) seed priming improves photosynthesis, growth, plant defense and yield of wheat under drought stress

Drought stress mitigation by endophytic microorganisms has the potential to enhance crop resilience. This research investigated the effects of M. anisopliae isolate MetA1 (MA) on drought tolerance in wheat plants by evaluating physiological, morphological, biochemical, and yield characteristics of two wheat genotypes, one being drought-susceptible (BR20) and another having drought withstanding capacities (BR28) in a pot experiment under moderate and severe drought conditions. Under drought conditions, root colonization by M. anisopliae ranged from 33.33 to 66.67%. M. anisopliae treated plants increased the plant photosynthetic capacities by increasing photosynthetic pigments, Phi2, gH+, vH+, LEF, ECSt, leaf thickness and decreasing PhiNO, PhiNPQ, NPQt and leaf angle mostly for both genotypes, which contributed significant improvement of plant biomass in drought conditions. Exceptionally, the seed primed with M. anisopliae noticeably improved root length (by up to 17.6%) under drought conditions corroborated with the plant's drought mitigating approach. The stress induced malondialdehyde and hydrogen peroxide levels were dropped significantly by improving enzymatic antioxidants, such as peroxidase, ascorbate peroxidase, superoxide dismutase, catalase, and glutathione S-transferase in both M. anisopliae -primed genotypes. Also, proline content increased in the leaves of M. anisopliae treated plant which indicates better osmotic adjustment. Finally, M. anisopliae seed priming increased yield and yield characteristics of both genotypes in drought as well as non-drought situations with 1000-grain weight improving by up to 41.77% under severe drought. The study proposes a further investigation of M. anisopliae's effect in field settings and its applicability to other crops. Collectively, these findings emphasize the practical potential of M. anisopliae seed priming in boosting wheat production under water-limited circumstances, presenting a realistic technique for minimizing the effect of drought on global food security.

Physiological Effects and Mechanisms of Chlorella vulgaris as a Biostimulant on the Growth and Drought Tolerance of Arabidopsis thaliana.

Microalgae have demonstrated biostimulant potential owing to their ability to produce various plant growth-promoting substances, such as amino acids, phytohormones, polysaccharides, and vitamins. Most previous studies have primarily focused on the effects of microalgal biostimulants on plant growth. While biomass extracts are commonly used as biostimulants, research on the use of culture supernatant, a byproduct of microalgal culture, is scarce. In this study, we aimed to evaluate the potential of Chlorella vulgaris culture as a biostimulant and assess its effects on the growth and drought tolerance of Arabidopsis thaliana, addressing the gap in current knowledge. Our results demonstrated that the Chlorella cell-free supernatant (CFS) significantly enhanced root growth and shoot development in both seedlings and mature Arabidopsis plants, suggesting the presence of specific growth-promoting compounds in CFS. Notably, CFS appeared to improve drought tolerance in Arabidopsis plants by increasing glucosinolate biosynthesis, inducing stomatal closure, and reducing water loss. Gene expression analysis revealed considerable changes in the expression of drought-responsive genes, such as IAA5, which is involved in auxin signaling, as well as glucosinolate biosynthetic genes, including WRKY63, MYB28, and MYB29. Overall, C. vulgaris culture-derived CFS could serve as a biostimulant alternative to chemical products, enhancing plant growth and drought tolerance.

Intraspecific Variability of Xylem Hydraulic Traits of Calligonum mongolicum Growing in the Desert of Northern Xinjiang, China.

Plant hydraulic traits are essential for understanding and predicting plant drought resistance. Investigations into the mechanisms of the xylem anatomical traits of desert shrubs in response to climate can help us to understand plant survival strategies in extreme environments. This study examined the xylem anatomical traits and related functional traits of the branches of seven Calligonum mongolicum populations along a precipitation gradient, to explore their adaptive responses to climatic factors. We found that (1) the vessel diameter (D), vessel diameter contributing to 95% of hydraulic conductivity (D95), hydraulic weighted vessel diameter (Dh), vessel density (VD), percentage of conductive area (CA), thickness-to-span ratio of vessels ((t/b)2), and theoretical hydraulic conductivity (Kth) varied significantly across sites, while the vessel group index (Vg), wood density (WD), and vulnerability index (VI) showed no significant differences. (2) Principal component analysis revealed that efficiency-related traits (Kth, Dh, D95) and safety-related traits (VI, VD, inter-wall thickness of the vessel (t)) were the primary factors driving trait variation. (3) Precipitation during the wettest month (PWM) had the strongest influence, positively correlating with (t/b)2 and negatively with D, D95, Dh, CA, and Kth. (4) Structural equation modeling confirmed PWM as the main driver of Kth, with indirect effects through CA. These findings indicate that C. mongolicum displays high plasticity in xylem traits, enabling adaptation to changing environments, and providing insight into the hydraulic strategies of desert shrubs under climate change.

Functional analysis of TkWRKY33: A key regulator in drought-induced natural rubber synthesis in Taraxacum kok-saghyz

WRKY proteins, which form a transcription factor superfamily that responds to jasmonic acid (JA) signals, regulate various developmental processes and stress responses in plants, including Taraxacum kok-saghyz (TKS). TKS serves as an ideal model plant for studying rubber production and lays the foundation for a comprehensive understanding of JA-mediated regulation of natural rubber synthesis. In the present study, we screened and identified a valuable transcription factor, TkWRKY33, based on transcriptome data from TKS in response to JA. We investigated its role in the regulation of natural rubber synthesis within the JA signaling pathway and its function in response to drought stress. Through protein-protein interactions and transcriptional regulation analysis, we found that TkWRKY33 may regulate natural rubber synthesis through the JA-TkMPK3-TkWRKY33-(TkGGPS5/TkACAT8) cascade pathway, possibly by participating in JA-activated mitogen-activated protein kinase (MAPK) signaling. Overexpression of TkWRKY33 in tobacco, along with functional analysis of drought resistance and comparative analysis of natural rubber content after drought stress, revealed that TkWRKY33 not only enhances plant drought resistance by regulating the expression of genes related to reactive oxygen species (ROS) scavenging through the JA signaling pathway, but also has a close relationship with the signal transduction pathway mediated by the JA hormone in regulating natural rubber synthesis.The TkWRKY33 is recognized as a valuable transcription factor, which likely plays a role in regulating natural rubber biosynthesis through the JA-activated MAPK cascade signaling pathway JA-TkMPK3-TkWRKY33-(TkGGPS5/TkACAT8).

Streptomyces improves sugarcane drought tolerance by enhancing phenylalanine biosynthesis and optimizing the rhizosphere environment

Drought stress is a common hazard faced by sugarcane growth, and utilizing microorganisms to enhance plant tolerance to abiotic stress has become an important method for sustainable agricultural development. Several studies have demonstrated that Streptomyces chartreuses WZS021 improves sugarcane tolerance to drought stress. However, the molecular mechanisms underlying tolerance at the transcriptional and metabolomic levels remain unclear. We comprehensively evaluated the physiological and molecular mechanisms by which WZS021 enhances drought tolerance in sugarcane, by performing transcriptome sequencing and non-targeted metabolomics; and examining rhizosphere soil properties and plant tissue antioxidant capacity. WZS021 inoculation improved the rhizosphere nutritional environment (AP, ammonia, OM) of sugarcane and enhanced the antioxidant capacity of plant roots, stems, and leaves (POD, SOD, CAT). Comprehensive analyses of the transcriptome and metabolome revealed that WZS021 mainly affects plant drought tolerance through phenylalanine metabolism, plant hormone signal transduction, and flavonoid biosynthesis pathways. The drought tolerance signaling molecules mediated by WZS021 include petunidin, salicylic acid, α-Linoleic acid, auxin, geranylgeraniol and phenylalanine, as well as key genes related to plant hormone signaling transduction (YUCCA, amiE, AUX, CYPs, PAL, etc.). Interestingly, inoculation with WZS021 during regular watering induces a transcriptome-level response to biological stress in sugarcane plants. This study further elucidates a WZS021-dependent rhizosphere-mediated regulatory mechanism for improving sugarcane drought tolerance, providing a theoretical basis for increasing sugarcane production capacity.

Drought Tolerance in Plants: Physiological and Molecular Responses.

Drought, a significant environmental challenge, presents a substantial risk to worldwide agriculture and the security of food supplies. In response, plants can perceive stimuli from their environment and activate defense pathways via various modulating networks to cope with stress. Drought tolerance, a multifaceted attribute, can be dissected into distinct contributing mechanisms and factors. Osmotic stress, dehydration stress, dysfunction of plasma and endosome membranes, loss of cellular turgidity, inhibition of metabolite synthesis, cellular energy depletion, impaired chloroplast function, and oxidative stress are among the most critical consequences of drought on plant cells. Understanding the intricate interplay of these physiological and molecular responses provides insights into the adaptive strategies plants employ to navigate through drought stress. Plant cells express various mechanisms to withstand and reverse the cellular effects of drought stress. These mechanisms include osmotic adjustment to preserve cellular turgor, synthesis of protective proteins like dehydrins, and triggering antioxidant systems to counterbalance oxidative stress. A better understanding of drought tolerance is crucial for devising specific methods to improve crop resilience and promote sustainable agricultural practices in environments with limited water resources. This review explores the physiological and molecular responses employed by plants to address the challenges of drought stress.

Gene Expression Analysis for Drought Tolerance in Early Stage of Potato Plant Development.

Drought has increasingly affected the yield of Solanum tuberosum L. (potato) every year over the last decade, posing serious economic problems for the global agricultural industry. Therefore, it is important to research drought tolerance in plants and obtain more robust varieties of crops. The aim of the present work was to study the expression of drought-upregulated genes in drought-tolerant and drought-sensitive varieties of potato. Bioreactors were used to identify whether each variety was drought-tolerant or drought-sensitive; then, expression analysis was performed according to the morphological characteristics of the plantlets in two different media: Murashige and Skoog (MS) medium and MS medium with 20% PEG-6000 to simulate osmotic stress. Based on the quantitative parameters of six initial varieties, two varieties were selected (Gala and Aksor) for further gene expression analysis. The expression of genes commonly upregulated in drought (ER24, TAS14, DREB147315, PP2C, 102605413 and NF-YC4) was higher in the drought-tolerant variety than in the sensitive one. Therefore, the expression of these genes can be used to determine the drought tolerance of a potato variety in vitro in the early plant development stage. Moreover, comparative analysis showed that some of the targeted genes used to identify drought tolerance in this study are conserved across different plant species.

A Positive Role for CaMEKK17 in Response to Drought Stress, Modulated by Clade A PP2Cs.

The abscisic acid (ABA) signaling pathway is essential for plant response to abiotic stresses and can be modulated positively or negatively by MAPKKK proteins. This study focuses on the functional characterization of CaMEKK17, a MAPKKK previously recognized for its rapid induction under drought stress. Functional analyses demonstrated that CaMEKK17 is an active serine/threonine kinase with a conserved catalytic domain that is crucial for its kinase activity. CaMEKK17 silencing in pepper plants resulted in reduced drought tolerance, characterized by increased transpirational water loss and impaired ABA-mediated stomatal closure. Conversely, CaMEKK17 overexpression in Arabidopsis increased kinase activity, enhancing ABA sensitivity and drought tolerance. Further investigation revealed that CaMEKK17 interacts with pepper group A type 2C protein phosphatases (PP2Cs), particularly CaAITP1 and CaAIPP1, which inhibit its kinase activity. Protein-protein interactions mediated inhibition by CaAITP1, whereas CaAIPP1 relied on its phosphatase activity. Double gene silencing of CaMEKK17 and CaAITP1 demonstrated that CaMEKK17 functions downstream of CaAITP1 in ABA-mediated drought tolerance. Taken together, our findings suggest that CaMEKK17 positively modulates drought tolerance in pepper plants but may be inhibited by PP2Cs.