An R2R3 MYB gene GhMYB3 functions in drought stress by negatively regulating stomata movement and ROS accumulation

Maize ZmWRKY71 gene positively regulates drought tolerance through reactive oxygen species homeostasis

Drought stress severely affects plant growth and yield. The plant-specific WRKY transcription factors play an important role in regulating the plant response to abiotic stresses. In this study, we identified a group I WRKY gene from maize, designated ZmWRKY71. Real-time quantitative reverse transcription-PCR analysis revealed that ZmWRKY71 was predominantly expressed in the roots and was induced by drought. ZmWRKY71 was localized in the nucleus and showed transcriptional activity in yeast. Heterologous overexpression of ZmWRKY71 improved drought tolerance in yeast and Arabidopsis. Compared with the wild type, the overexpression lines showed a higher survival rate under drought stress with reduced malondialdehyde content and elevated antioxidant enzyme activities. In contrast, mutation of ZmWRKY71 in maize leads to increased sensitivity to drought stress, reduced survival, elevated concentrations of reactive oxygen species, and increased malondialdehyde content. RNA-sequencing analysis revealed that the expression patterns of genes associated with translation, membrane, and oxidoreductase activity pathways were altered under drought stress. Yeast one-hybrid, dual-luciferase, and electrophoretic mobility shift assays confirmed that ZmWRKY71 was capable of directly binding to the W-box element in the promoter region of ZmPOD42 (Zm00001eb330550). Taken together, the results show that ZmWRKY71 positively regulates maize drought tolerance. This research enriches the drought tolerance gene pool for maize and provides a theoretical basis for maize drought tolerance breeding.

A R2R3-MYB transcription factor, FeR2R3-MYB, positively regulates anthocyanin biosynthesis and drought tolerance in common buckwheat (Fagopyrum esculentum)

The R2R3-MYB transcription factors (TFs) play a crucial role in regulating plant secondary metabolism and abiotic stress responses, yet they are still poorly understood in common buckwheat (Fagopyrum esculentum), a valuable minor grain crop resource. In this study, a candidate gene, FeR2R3-MYB, was cloned from the anthocyanin-rich common buckwheat variety 'QZZTQ'. FeR2R3-MYB was found to contain two MYB DNA-binding domains and be located at the nucleus with transcriptional activation activity. Molecular analysis indicated that FeR2R3-MYB is predominantly expressed in flowering tissue and is highly responsive to environmental factors such as light, drought, and cold. In addition, the promoter of FeR2R3-MYB showed a positive correlation with fragment length. Further functional analysis suggested that FeR2R3-MYB not only participates in the anthocyanin biosynthetic pathway by interacting with leucoanthocyanidin reductase (FeLAR), but also enhances drought tolerance in common buckwheat. To sum up, FeR2R3-MYB exhibits positive effects on both pigment production (e.g., anthocyanin) and abiotic stress resistance, providing valuable insights for future research in buckwheat molecular breeding and resource development.

Function of MYB8 in larch under PEG simulated drought stress

Larch, a prominent afforestation, and timber species in northeastern China, faces growth limitations due to drought. To further investigate the mechanism of larch's drought resistance, we conducted full-length sequencing on embryonic callus subjected to PEG-simulated drought stress. The sequencing results revealed that the differentially expressed genes (DEGs) primarily played roles in cellular activities and cell components, with molecular functions such as binding, catalytic activity, and transport activity. Furthermore, the DEGs showed significant enrichment in pathways related to protein processing, starch and sucrose metabolism, benzose-glucuronic acid interconversion, phenylpropyl biology, flavonoid biosynthesis, as well as nitrogen metabolism and alanine, aspartic acid, and glutamic acid metabolism. Consequently, the transcription factor T_transcript_77027, which is involved in multiple pathways, was selected as a candidate gene for subsequent drought stress resistance tests. Under PEG-simulated drought stress, the LoMYB8 gene was induced and showed significantly upregulated expression compared to the control. Physiological indices demonstrated an improved drought resistance in the transgenic plants. After 48 h of PEG stress, the transcriptome sequencing results of the transiently transformed LoMYB8 plants and control plants exhibited that genes were significantly enriched in biological process, cellular component and molecular function. Function analyses indicated for the enrichment of multiple KEGG pathways, including energy synthesis, metabolic pathways, antioxidant pathways, and other relevant processes. The pathways annotated by the differential metabolites mainly encompassed signal transduction, carbohydrate metabolism, amino acid metabolism, and flavonoid metabolism.

Transcription factors as molecular switches regulating plant responses to drought stress

Plants often experience abiotic stress, which severely affects their growth. With the advent of global warming, drought stress has become a pivotal factor affecting crop yield and quality. Increasing numbers of studies have focused on elucidating the molecular mechanisms underlying plant responses to drought stress. As molecular switches, transcription factors (TFs) are key participants in drought-resistance regulatory networks in crops. TFs regulate the transcription of downstream genes and are regulated by various upstream regulatory factors. Therefore, understanding the mechanisms of action of TFs in regulating drought stress can help enhance the adaptive capacity of crops under drought conditions. In this review, we summarize the structural characteristics of several common TFs, their multiple drought-response pathways, and recently employed research strategies. We describe the application of new technologies such as analysis of stress granule dynamics and function, multi-omics data, gene editing, and molecular crosstalk between TFs in drought resistance. This review aims to familiarize readers with the regulatory network of TFs in drought resistance and to provide a reference for examining the molecular mechanisms of drought resistance in plants and improving agronomic traits.

Ectopic expression of HaPEPC1 from the desert shrub Haloxylon ammodendron confers drought stress tolerance in Arabidopsis thaliana

Phosphoenolpyruvate carboxylase (PEPC) plays a crucial role in the initial carbon fixation process in C4 plants. However, its nonphotosynthetic functions in Haloxylon ammodendron, a C4 perennial xerohalophytic shrub, are still poorly understood. Previous studies have reported the involvement of PEPC in plant responses to abiotic stresses such as drought and salt stress. However, the underlying mechanism of PEPC tolerance to drought stress has not been determined. In this study, we cloned the C4-type PEPC gene HaPEPC1 from H. ammodendron and investigated its biological function by generating transgenic Arabidopsis plants with ectopic expression of HaPEPC1. Our results showed that, compared with WT (wild-type) plants, ectopic expression of HaPEPC1 plants exhibited significantly greater germination rates and chlorophyll contents. Furthermore, under drought stress, the transgenic plants presented increased root length, fresh weight, photosynthetic capacity, and antioxidant enzyme activities, particularly ascorbate peroxidase and peroxidase. Additionally, the transgenic plants exhibited reduced levels of malondialdehyde, H2O2 (hydrogen peroxide), and O2- (superoxide radical). Transcriptome analysis indicated that ectopic expression of HaPEPC1 primarily regulated the expression of genes associated with the stress defence response, glutathione metabolism, and abscisic acid (ABA) synthesis and signalling pathways in response to drought stress. Taken together, these findings suggest that the ectopic expression of HaPEPC1 enhances the reduction of H2O2 and O2- in transgenic plants, thereby improving reactive oxygen species (ROS) scavenging capacity and enhancing drought tolerance. Therefore, the HaPEPC1 gene holds promise as a candidate gene for crop selection aimed at enhancing drought tolerance.

A Multi-Omics Analysis Revealed the Diversity of the MYB Transcription Factor Family's Evolution and Drought Resistance Pathways

The MYB transcription factor family can regulate biological processes such as ABA signal transduction to cope with drought stress, but its evolutionary mechanism and the diverse pathways of response to drought stress in different species are rarely reported. In this study, a total of 4791 MYB family members were identified in 908,757 amino acid sequences from 12 model plants or crops using bioinformatics methods. It was observed that the number of MYB family members had a linear relationship with the chromosome ploidy of species. A phylogenetic analysis showed that the MYB family members evolved in subfamily clusters. In response to drought stress, the pathways of MYB transcription factor families exhibited species-specific diversity, with closely related species demonstrating a higher resemblance. This study provides abundant references for drought resistance research and the breeding of wheat, soybean, and other plants.

Genetic and Epigenetic Responses of Autochthonous Grapevine Cultivars from the 'Epirus' Region of Greece upon Consecutive Drought Stress

Within the framework of preserving and valorizing the rich grapevine germplasm of the Epirus region of Greece, indigenous grapevine (Vitis vinifera L.) cultivars were characterized and assessed for their resilience to abiotic stresses in the context of climate change. The cultivars 'Debina' and 'Dichali' displayed significant differences in their response to drought stress as judged by morpho-physiological analysis, indicating higher drought tolerance for Dichali. Hence, they were selected for further study aiming to identify genetic and epigenetic mechanisms possibly regulating drought adaptability. Specifically, self-rooted and heterografted on 'Richter 110' rootstock plants were subjected to two phases of drought with a recovery period in between. Gene expression analysis was performed for two stress-related miRNAs and their target genes: (a) miRNA159 and putative targets, VvMYB101, VvGATA-26-like, VvTOPLESS-4-like and (b) miRNA156 and putative target gene VvCONSTANS-5. Overall, grafted plants exhibited a higher drought tolerance than self-rooted plants, suggesting beneficial rootstock-scion interactions. Comparative analysis revealed differential gene expression under repetitive drought stresses between the two cultivars as well as between the self-rooted and grafted plants. 'Dichali' exhibited an up-regulation of most of the genes examined, which may be associated with increased tolerance. Nevertheless, the profound down-regulation of VvTOPLESS-4-like (a transcriptional co-repressor of transcription factors) upon drought and the concomitant up-regulation of miRNA159 highlights the importance of this 'miRNA-target' module in drought responsiveness. DNA methylation profiling using MSAP analysis revealed differential methylation patterns between the two genotypes in response to drought. Further investigations of gene expression and DNA methylation will contribute to our understanding of the epigenetic mechanisms underlying grapevine tolerance to drought stress.

Genome-Wide Characterization of bHLH Family Genes and Expression Analysis in Response to Osmotic Stress in Betula platyphylla

The bHLH family, as a superfamily of transcription factors (TFs), has special functional characteristics in plants and plays a crucial role in a plant's growth and development and helping the plant cope with various stresses. In this study, 128 bHLH family genes were screened in the birch (B. platyphylla) genome using conservative domain scan and blast analysis. These genes are clustered into 21 subfamilies based on the phylogenetic tree construction and are unevenly distributed among the 14 birch chromosomes. In all, 22 segmental duplication pairs with 27 BpbHLH genes were identified. The duplications were distributed on eight chromosomes. Analysis of gene structures and protein motifs revealed intra-group conservation of BpbHLHs. Of the BpbHLH family genes, 16 contain only one intron each. The BPChr14G06667 gene contains the most introns, that is, 19. The cis-elements, which respond to plant hormones, light, defense, and stress, were found on the promoter of BHLH family genes. As per RNA-seq data analysis, under PEG osmotic stress, most BpbHLH genes were differentially expressed, and eight were highly differentially expressed. The qRT-PCR analysis results further indicated that BPChr06G09475 was the gene with the highest expression level in leaves, roots, and stems, and that the expression of these eight genes was higher in leaves than in roots and stems and upregulated in all three tissues under osmotic stress compared to the controls. The above analysis suggests that the BpbHLH family genes have a certain biological effect under drought stress that provides a basis for molecular breeding for stress resistance in birch.

AeWRKY32 from okra regulates anthocyanin accumulation and cold tolerance in Arabidopsis

Okra (Abelmoschus esculentus L.) is a tropical crop species, and its growth and development are severely affected by cold stress. Recent studies have identified a potential association between WRKY transcription factors and the cold response mechanism of crops. In this study, the AeWRKY32 transcription factor that encodes 482 amino acids was amplified from A. esculentus, and its expression level was found to be the highest in the okra flower. AeWRKY32 localized to the nucleus and displayed transcriptional activation capability. Under normal conditions, overexpression of AeWRKY32 induced anthocyanin accumulation, with higher expression levels of AtCHS1, AtCHI4, AtF3H1, and AtDFR2 in transgenic Arabidopsis. Under cold stress, anthocyanin levels were further elevated in transgenic Arabidopsis plants. At the same time, AeWRKY32 overexpression promoted ABA biosynthesis, inhibited H2O2 and O2- generation, induced stomatal closure, reduced electrolyte leakage, and thus improved the cold resistance of transgenic Arabidopsis. Furthermore, under cold stress, the expression profiles of AtCOR413, AtCOR15B, AtCBF1, and AtCBF2 were upregulated in transgenic Arabidopsis. Overall, our study provides evidence that AeWRKY32 serves as a crucial regulator in both anthocyanin accumulation and cold tolerance of transgenic Arabidopsis. Our findings could provide insights into the molecular mechanism linking AeWRKYs to plant cold tolerance.