RcAP2L ‐ RcAS1 complex modulates petal number in roses by targeting RcAGL80 promoter

SUMMARY Double flower, which is one of the most important characteristics of ornamental plants, is closely related to their ornamental and commercial value. The double‐flower trait in rose was mainly due to the increase in petal number caused by stamen petalization. However, the mechanism regulating petal number is not clear. In this study, the Rosa chinensis “Zhaiye Tengben Yuejihua” × R. chinensis “Old Blush” population was used for QTL detection and NGS‐based BSA analysis to identify candidate genes related to petal number. It was found that RcAP2L and RcAS1 were highly expressed in double‐flower rose, while RcAGL80 was highly expressed in single‐flower rose. Silencing RcAP2L and RcAS1 reduced the petal number by inhibiting homeotic conversion of stamens to petals, separately. However, silencing RcAGL80 increased the petal number by promoting homeotic conversion of stamens to petals. The results of Y2H and BiFC assays showed that RcAP2L interacted with RcAS1. The dual‐luciferase assay showed that RcAP2L was bound to the promoter of RcAGL80 and suppressed RcAGL80 transcription. In total, we found a new function of AS1 in specifying flower organ identity, and a new pathway for regulating the number of petals by RcAS1 , RcAGL80 , and RcAP2L , which provides new information for elucidating the mechanism of the formation of double flower in rose.