Genome-Wide Characterization and Expression Profiling of the CCR Gene Family Associated with Stem Strength in Upland Cotton (Gossypium hirsutum L.)

In this study, we performed the first genome-wide identification and characterization of the cinnamoyl-CoA reductase (CCR) gene family in upland cotton (Gossypium hirsutum), focusing on its potential association with stem strength. We identified 76 GhCCR genes and classified them into four subfamilies. We then analyzed their evolutionary relationships, conserved domains, synteny, promoter cis-elements, and expression patterns. All GhCCR proteins possess the NADB_Rossmann superfamily domain, and family expansion appears to have been driven mainly by segmental and tandem duplications. A small number of GhCCR genes showed relatively high expression in leaf, pistil, and torus tissues, while genes such as GhCCR3/9/10 exhibited elevated transcript levels under abiotic stress conditions. RT-qPCR results indicated that three candidate GhCCR genes (GhCCR25, GhCCR52 and GhCCR64) were significantly more highly expressed in multiple tissues of the stiff-stem line JY-25 than in the soft-stem line JR-15. Together, these findings suggest that GhCCR genes may contribute to the regulation of growth, development, and stress adaptation in G. hirsutum. However, direct biochemical or genetic validation is required to confirm their functional roles in lignin biosynthesis and stem rigidity.