Genome-Wide Bioinformatics Identification and Functional Analysis of the 3-ketoacyl-CoA Synthase (KCS) Gene Family in Rosa × hybrida, with Focus on RcKCS6

Background/Objectives: The 3-ketoacyl-CoA synthase (KCS) enzyme is a key and rate-limiting component in the biosynthesis of very long-chain fatty acids (VLCFAs). Through controlling VLCFA production, KCS plays an essential role in plant cuticle formation. The necrotrophic fungus Botrytis cinerea can infect all aboveground parts of rose plants (flowers, leaves, and stems), causing severe economic losses. KCS restricts pathogen invasion by influencing cuticle formation and enhances tolerance to environmental stresses. While the KCS gene family has been well-studied in some plants, it remains unexplored in rose (Rosa × hybrida Hort.), a species of significant ornamental and economic value. Methods: In this study, we conducted a genome-wide analysis of the RcKCS gene family in rose, identifying 18 non-redundant genes. Phylogenetic, structural, and synteny analyses were performed to investigate the evolutionary relationships, gene architecture, and duplication events. The expression patterns of RcKCS genes in rose petals during Botrytis cinerea infection were examined, and transient overexpression and silencing of RcKCS6 were used to study its function. Results: RcKCS6 was found to be upregulated during gray mold infection, and transient overexpression reduced lesion size on infected petals. Conclusions: Our study provides the first comprehensive analysis of the RcKCS gene family in rose and highlights RcKCS6 as a potential candidate for improving resistance to gray mold in rose through molecular breeding.