Background: DNA methylation is an important epigenetic mode of genomic DNA modification and plays a vital role in maintaining epigenetic content and regulating gene expression. Cytosine-5 DNA methyltransferase (C5-MTase) are the key enzymes in the process of DNA methylation. However, there is no systematic analysis of the C5-MTase in cotton so far, and the function of DNMT2 genes has not been studied. Methods: In this study, the whole genome of cotton C5-MTase coding genes was identified and analyzed using a bioinformatics method based on information from the cotton genome, and the function of GhDMT6 was further validated by VIGS experiments and subcellular localization analysis. Results: 33 C5-MTases were identified from three cotton genomes, and were divided into four subfamilies by systematic evolutionary analysis. After the protein domain alignment of C5-MTases in cotton, 6 highly conserved motifs were found in the C-terminus of 33 proteins involved in methylation modification, which indicated that C5-MTases had a basic catalytic methylation function. These proteins were divided into four classes based on the N-terminal difference, of which DNMT2 lacks the N-terminal regulatory domain. The expression of C5-MTases in different parts of cotton was different under different stress treatments, which indicated the functional diversity of cotton C5-MTase gene family. Among the C5-MTases, the GhDMT6 had a obvious up-regulated expression. After silencing GhDMT6 with VIGS, the phenotype of cotton seedlings under different stress treatments showed a significant difference. Compared with cotton seedlings that did not silence GhDMT6, cotton seedlings silencing GhDMT6 showed significant stress resistance. Conclusion: The results show that C5-MTases plays an important role in cotton stress response, which is beneficial to further explore the function of DNMT2 subfamily genes.

Short-season cotton is a type of cotton variety characterized by its abbreviated cycle, rapid development, and concentrated flowering and boll setting. Compared with full-season cotton, short-season cotton facilitates an easier attainment of desirable maturation even when sown relatively late. This advantage of late sowing and early maturation eliminates the necessity for plastic film mulching, thereby creating opportunities for diversified double cropping, such as cotton–wheat, cotton–garlic, cotton–rape, and cotton–triticale systems. This paper provides a comprehensive review of the morphological, physiological, and molecular biological mechanisms underlying early maturity in short-season cotton. Furthermore, the significance and application of short-season cotton is discussed in relation to optimizing planting patterns and methods, promoting its cultivation in saline fields, developing machine-harvested cotton, and encouraging plastic mulch-free cotton planting. Based on these analyses and discussions, the paper proposes future strategies aimed at enhancing the breeding and cultivation of short-season cotton. These findings serve as valuable references for global breeding and cultivation research, and application of short-season cotton in the future.

Vitamin C, also referred to as ascorbic acid (AsA), is recognized for its capacity to cure and avert scurvy, and it is crucial for regular human growth and development. In various crops, AsA participates in stress response mechanisms mediated by abscisic acid and has been discovered to have a crucial function in the morphogenesis, growth, development, and production of male gametes in plants. GDP-D-mannose 3′,5′-epimerase (GME) is essential in the synthesis of vitamin C. Our research identified 91, 83, 51, and 46 genes, respectively, found in G. barbadense (GbGMEs), G. hirsutum (GhGMEs), G. arboretum (GaGMEs), and G. raimondii (GrGMEs). Plants resulting from VIGS infection with GhGME31D clearly showed yellowing, water loss and wilting of leaves and black spots on stems. Measurement of MDA and AsA levels indicated that the plants were more damaged. This indicates that AsA has a substantial impact on plant growth and development.

Although fatty acyl-CoA reductase (FAR) proteins are known to play essential roles in plant growth and development, their involvement in biotic and abiotic stress responses remains insufficiently characterized. In this study, we performed a comprehensive genome-wide analysis of 31 FAR genes across four cotton species (Gossypium arboreum, G. raimondii, G. hirsutum, and G. barbadense). Phylogenetic and synteny analyses classified these FAR genes into three distinct clades, with whole-genome duplication events contributing significantly to their expansion. Promoter cis-element analysis and transcriptome profiling revealed that while most FAR genes were downregulated under abiotic stress, many were notably upregulated in response to hormone treatments and Verticillium dahliae infection. Among them, GhFAR3 showed strong induction upon pathogen challenge. Functional validation using virus-induced gene silencing (VIGS) demonstrated that silencing GhFAR3 compromised resistance to V. dahliae, correlating with a marked reduction in suberin deposition in root tissues. These findings uncover a previously unrecognized role of FAR-mediated lipid metabolism in plant defense and establish GhFAR3 as a key positive regulator of cotton resistance to V. dahliae through suberin biosynthesis in roots. This study provides novel insights into the integration of lipid biosynthesis and pathogen resistance pathways in cotton.

Tryptophan decarboxylase (TDC) is the rate-limiting enzyme in the biosynthesis of melatonin and plays a crucial role in melatonin production in plants. Melatonin (MT), a multifunctional indoleamine compound, plays a pivotal role in plant responses to abiotic stress. Substantial evidence has demonstrated that MT can significantly enhance plant tolerance to drought stress. However, the molecular mechanisms underlying MT-mediated drought stress responses in plants remain unclear. This study systematically analyzed the evolutionary relationships of the TDC gene family in four cotton species using bioinformatics approaches, including phylogenetic analysis, chromosomal localization, gene structure, conserved motifs, cis-acting elements, synteny, and expression patterns. Functional characterization of GhTDC5 in Gossypium hirsutum was performed using virus-induced gene silencing (VIGS), with the following key findings: gene silencing efficiency reached 67.5%, leading to a significant 50.31% reduction in melatonin content. Under drought stress, silenced plants exhibited a 46.56% decrease in leaf water content, 23.01% reduction in chlorophyll content, and more severe wilting symptoms compared to controls. Impaired antioxidant system: significant decreases in peroxidase (POD) and superoxide dismutase (SOD) activities as well as proline (Pro) content, along with increased malondialdehyde (MDA) and ROS accumulation. Exogenous melatonin treatment effectively scavenged superoxide anions and alleviated drought stress. The results demonstrate that GhTDC5 plays a crucial role in cotton drought resistance by regulating melatonin biosynthesis. This study not only elucidates the evolutionary characteristics of the TDC gene family but also provides important theoretical foundations and candidate genes for drought-resistant cotton breeding.