Genome-Wide Evolution and Stress-Responsive Regulation of 2-Oxoglutarate-Dependent Dioxygenases in Gossypium

Purpose: Gibberellins (GAs) are key phytohormones that regulate plant growth, development, and responses to environmental stress, and their metabolism is mediated by 2-oxoglutarate-dependent dioxygenases (2OGDs). Cotton (Gossypium spp.) is a polyploid crop with a complex genome; however, the evolutionary characteristics and stress-responsive regulation of GA-related 2OGDs remain poorly understood. This study aimed to systematically investigate the evolution, expression patterns, and stress-associated regulation of the cotton 2OGD multigene family, with particular emphasis on GA-related members. Methods: 2OGD genes were identified genome-wide in four Gossypium species and Arabidopsis thaliana. Phylogenetic relationships, gene structures, conserved motifs, cis-acting regulatory elements, and synteny were analyzed. Transcriptomic data from multiple tissues and developmental stages, together with time-course RNA-seq under salt stress, were examined. Transcriptome–metabolome association analysis, endogenous GA quantification, and predicted protein–protein interaction analysis were conducted. Results: A total of 583 2OGD genes were identified and classified into three major classes, including a Class C group comprising GA2ox, GA3ox, and GA20ox genes. Polyploidization-associated duplication contributed to the expansion of the 2OGD family, and most duplicated gene pairs exhibited signatures of purifying selection. GA-related 2OGDs displayed conserved motif compositions with variation in cis-acting elements. Promoter analysis identified abundant hormone-responsive, stress-responsive, and growth-related cis-elements, suggesting complex regulatory control of GA-related 2OGDs in cotton. Under salt stress, GhGA2OX1 and GhGA20OX2 were upregulated, whereas GhGA3OX1 was downregulated, accompanied by reduced endogenous GA levels. Conclusions: GA-related 2OGDs in cotton are transcriptionally responsive to salt stress and are associated with changes in GA metabolism, providing a basis for future functional studies.