GhSCL5, a GRAS transcription factor from cotton, positively regulates drought tolerance by modulating phytohormone signaling and carbon metabolism.

In this study, we functionally characterized the GRAS transcription factor gene GhSCL5 in upland cotton. Transcriptome analysis, RT-qPCR validation, and public transcriptome data from the CottonOmics database demonstrated that the expression of GhSCL5 was significantly induced by exogenous γ-polyglutamic acid (γ-PGA), polyethylene glycol (PEG)-simulated drought, and natural drought conditions. These results indicate that GhSCL5 participates in the drought stress response of cotton. Drought is a major abiotic stress limiting cotton production. The GRAS protein family participates in plant development and abiotic stress responses, but the roles of many cotton GRAS members remain unclear. Here, we characterized GhSCL5, a GRAS family gene in upland cotton (Gossypium hirsutum) whose expression was induced by natural drought, polyethylene glycol (PEG), and exogenous γ-polyglutamic acid (γ-PGA). Silencing GhSCL5 by virus-induced gene silencing (VIGS) reduced cotton drought tolerance, as indicated by decreased catalase (CAT) and peroxidase (POD) activities, lower proline (Pro) accumulation and leaf relative water content (RWC), and increased malondialdehyde (MDA) content under drought stress. Conversely, heterologous overexpression of GhSCL5 in Arabidopsis thaliana enhanced drought tolerance and maintained longer primary roots under mannitol-induced osmotic stress. Transcriptome profiling identified 7061 differentially expressed genes (DEGs) in GhSCL5-silenced cotton leaves under drought stress, comprising 3140 upregulated and 3921 downregulated genes. Notably, upregulated DEGs were enriched in pathways, including plant-pathogen interaction, plant hormone signal transduction, the plant MAPK signaling pathway, amino sugar and nucleotide sugar metabolism, phenylpropanoid biosynthesis, and arginine and proline metabolism, while downregulated DEGs were enriched in photosynthesis, plant hormone signal transduction, starch and sucrose metabolism, carbon fixation in photosynthetic organisms, glyoxylate and dicarboxylate metabolism, and photosynthesis-antenna protein. Importantly, the plant hormone signal transduction pathway was enriched with both upregulated and downregulated DEGs, suggesting that this pathway may represent a significant component of the transcriptional response. Within the plant hormone signal transduction pathway, genes associated with abscisic acid (ABA) and auxin were the most abundant, which indicates that these two hormonal systems might be key factors in the response associated with GhSCL5. Collectively, these findings suggest that GhSCL5 may contribute to drought tolerance through processes related to antioxidant defense, osmotic adjustment, and carbon metabolism, with transcriptomic evidence suggesting a potential involvement of ABA and Auxin signaling.