Expansion and expression diversity of genes provides insights into flowering time regulation in roses.

Roses are important horticultural plants with enormous diversity in flowers and flowering behavior. However, molecular regulation of flowering time variation in roses remains poorly characterized. Here, we report an expansion of the genes that correlates well with the switch to prostrate-to-erect growth of shoots upon flowering in 'Basye's Thornless' (BT). With the availability of the high-quality chromosome-level genome assembly for BT that we developed recently, we identified 91 genes, a significant expansion in contrast to 52 in 'Old Blush' (OB), a founder genotype in modern rose domestication. Rose FAR1/FRS-like proteins feature distinct variation in protein domain structures. The dispersed expansion of genes occurred specifically in clade I and II and is significantly associated with transposon insertion in BT. Most of the genes showed relatively higher expression level than their corresponding orthologs in OB. genes regulate light-signaling processes, shade avoidance, and flowering time in . Therefore, the expansion and duplication of genes, followed by diversification in gene expression, might offer a novel leverage point for further understanding the molecular regulation of the variation in shoot-growth behavior and flowering time in roses.