Background: Green cotton fibers (GCFs) are valued for their natural coloration and eco-friendly properties, but their pigmentation mechanisms remain unclear, limiting their wider application in the textile industry. This study aims to uncover the key regulatory genes and metabolic pathways involved in GCF coloration. Methods: We conducted transcriptome and metabolome profiling of green and white cotton fibers at different developmental stages to identify differences in gene expression and metabolite accumulation related to pigmentation. Results: Transcript analysis revealed significant enrichment in α-linolenic acid metabolism, flavonoid biosynthesis and phenylpropane metabolism pathways during late pigmentation stages. Key genes in methyl jasmonate (MeJA) biosynthesis and flavonoid biosynthesis (LOX, JMT, ANS, C4H, DFR, F3H) were upregulated. The MYB transcription factor showed the most significant increase during fiber development. Metabolomic analysis identified 12 metabolites that accumulated specifically in green fibers. MeJA treatment promoted the expression of MYB genes and flavonoid biosynthesis genes (DFRs, ANSs, F3H, C4H), as well as the accumulation of Luteolin, Gallocatechin, Cyanidin and Chrysanthemum metabolites. Conclusions: Our study demonstrates that MeJA-mediated flavonoid biosynthesis, regulated by MYB transcription factors, is the central pathway controlling pigment deposition in GCFs. These findings provide valuable insights for developing improved colored cotton materials.

This research centers on the sand-fixing plant known as Stipagrostis pennata, from which the β-glucosidase gene SpBGLU25 was successfully cloned using the molecular cloning method. SpBGLU25 encodes a hydrophilic and stable protein made up of 193 amino acids, located in the cell membrane. qRT-PCR analysis indicated that the expression of the SpBGLU25 is closely linked to the drought stress tolerance of S. pennata. Following this, functional validation was performed using an Arabidopsis overexpression system. The overexpression of transgenic Arabidopsis lines showed significantly improved drought tolerance under PEG and mannitol treatments. Assessments of germination, root length, and physiological indicators such as proline, malondialdehyde content, soluble sugars, and relative leaf water content (RLWC) further confirmed the enhanced performance of the overexpressing plants. Additionally, the comparative transcriptomic analysis of SpBGLU25-OE Arabidopsis compared to the wild-type (WT) showed that differentially upregulated genes were primarily enriched in categories of “cellular process,” “cell,” and “catalytic activity.” KEGG pathway enrichment analysis indicated that the genes were mainly concentrated in the pathways of phenylpropanoid biosynthesis and plant hormone signal transduction. These findings provide a crucial foundation for further investigation into the function of the SpBGLU25 and its role in regulating plant tissue development and adaptation to stress. This research is anticipated to offer new theoretical insights and genetic resources for enhancing plant stress tolerance through genetic engineering.

Verticillium wilt (VW), caused by the soil-borne fungus Verticillium dahliae, is a major disease that markedly compromises both the yield and fiber quality of cotton. In this study, we explored the function and underlying mechanism of the cotton expansin gene GhEXLB2 in response to VW infection. Expression profiling revealed that members of the GhEXL family exhibit distinct patterns across tissues and under various biotic and abiotic stresses. Notably, GhEXLB2, which encodes an extracellular protein, showed the strongest induction following V. dahliae challenge. Ectopic expression of GhEXLB2 in Arabidopsis thaliana promoted root elongation and root hair formation, and was associated with improved resistance to the pathogen. In contrast, silencing GhEXLB2 in cotton via virus-induced gene silencing (VIGS) led to pronounced vascular browning, increased pathogen recovery, and a lower level of disease resistance. In addition, RNA-seq profiling of GhEXLB2-silenced (VIGS) cotton plants revealed that most differentially expressed genes were enriched in pathways related to phytohormone signaling and plant–pathogen interactions, with salicylic acid (SA) signaling and WRKY transcription factors emerging as central regulatory components. Analysis of the GhEXLB2 promoter further identified multiple cis-acting elements associated with stress and hormone responsiveness. When integrated with protein–protein interaction (PPI) prediction data, these results suggest that GhEXLB2 may be modulated by a network of transcription factors and signaling pathways. Collectively, the evidence supports a positive association between GhEXLB2 and VW resistance. This study provides a framework for understanding expansin functions in cotton defense against VW.

Allene oxide cyclase (AOC) is an integral enzyme in jasmonic acid (JA) biosynthesis and a key regulator of plant stress responses. However, the regulatory mechanisms and enzymatic activities of cotton AOC under stress responses remain poorly understood. In our research, using BLASTP and conserved domain validation, we identified 68 AOC gene members across 10 Gossypium species. Phylogenetic, gene-structure, and syntenic analyses showed high evolutionary conservation of AOC genes, accompanied by lineage-specific expansion. Promoter sequence analysis indicated that the AOCs contained abundant cis-elements associated with hormone signaling, abiotic-stress response, and transcription factor (TF) regulation. Expression profiling revealed tissue-specific and stress-responsive expression patterns among GhAOC genes, with GhAOC3A showing the most pronounced upregulation under chilling stress. GhAOC3A was identified as a chloroplast-localized protein based on the subcellular localization assay. GhAOC3A overexpression enhanced cotton chilling tolerance with elevated JA accumulation, stronger antioxidant defense, stable osmotic homeostasis, and retained chlorophyll content, and VIGS results provided supportive evidence for the function of GhAOC3A in chilling tolerance. Among the predicted TFs that could regulate the expression of GhAOC3A, GhWRKY65 was further identified and confirmed to bind to the W-box element and activate GhAOC3A transcription. Overexpression of GhWRKY65 significantly enhanced cotton chilling tolerance, as well as elevated GhAOC3A expression and increased JA accumulation. Conversely, silencing GhWRKY65 compromised cotton chilling tolerance. Collectively, these findings suggest that the GhWRKY65-GhAOC3A regulatory module positively modulates cotton chilling tolerance and JA levels. Our study provides insights into the transcriptional network associated with plant stress response and offers effective candidates for breeding chilling-tolerant cotton materials.