Genome-Wide Identification and Expression Analysis of the HCT Gene Family in Upland Cotton (Gossypium hirsutum L.) in Response to Verticillium wilt Infection

Cotton, a globally vital cash crop, is severely constrained by V. dahliae. Lignin, a core structural component of plant cell walls, plays a crucial role in physical defense, with its biosynthesis regulated by hydroxycinnamoyltransferase (HCT)—a key enzyme in the phenylpropanoid pathway. However, the HCT gene family in upland cotton (Gossypium hirsutum) and its role in resistance to V. dahliae remain poorly understood. In this study, we performed a genome-wide identification of the HCT gene family in G. hirsutum, identifying 74 GhHCT genes that were classified into five evolutionary subfamilies. Bioinformatics analysis revealed that GhHCT proteins exhibit conserved functional domains but diverse gene structures, with promoter regions enriched in hormone-responsive and stress-responsive cis-acting elements. Expression profiling revealed that multiple GhHCT genes were significantly induced in response to V. dahliae infection. Three genes, GhHCT2, GhHCT35, and GhHCT47, showed significantly higher expression levels in resistant cultivars than in susceptible cultivars during early infection stages, suggesting pivotal roles in defense. These three candidate genes, which contain MeJA/SA-responsive elements in their promoters, may enhance resistance by regulating lignin synthesis to strengthen the cell wall barrier. In summary, this study provides the first comprehensive characterization of the HCT gene family in upland cotton. It identifies key candidates for improving resistance to V. dahliae, offering valuable genetic resources for molecular breeding.