Functional analysis of TRY from Rosa roxburghii (RrTRY) involved in prickle development and response to cytokinin

The aerial organs of Rosa roxburghii Tratt (RR), an economically important fruit crop endemic to southwestern China, have a dense prickle covering that severely impedes horticultural practices and industrial processing. Given the conserved role of R3MYB family members in inhibiting trichome formation in Arabidopsis thaliana, we systematically identified four R3MYB genes in the RR genome based on their conserved motifs. Promoter analysis revealed the presence of hormone-related elements in the promoter regions of the four R3MYB genes. Transcriptome data and qRT-PCR analysis revealed specific expression of RrTRY in prickle-free tissue. Subcellular localization analysis showed that RrTRY is targeted to both the nucleus and plasma membrane. Heterologous expression of RrTRY in A.thaliana suppressed trichome initiation, and in silico promoter analysis identified a cytokinin (CTK)-responsive cis-element. Exogenous CTK application restored trichome formation in transgenic A. thaliana, promoting endogenous AtTRY expression but suppressing RrTRY transcripts. Similarly, CTK application significantly increased the prickle density on leaf veins and young stems and downregulated RrTRY expression in RR seedlings. Our results demonstrate that CTK promotes prickle formation by repressing the negative regulator RrTRY, providing crucial molecular insights into prickle development and a strategic foundation for breeding prickle-free cultivars.