PpBSBRL Promotes Adventitious Root Formation in Peach via Interaction and Activation of PpSBRL

LBD transcription factors play pivotal roles in regulating adventitious root formation in plants, with two key LBD genes, SBRL and BSBRL, constituting the highly conserved superlocus first reported in tomato. However, the members of LBD genes regulating adventitious root formation in peach trees have not yet been identified, and the regulatory mechanisms of the two key LBD genes remain to be elucidated. In this study, through genome-wide analysis of the LBD gene family in peach, we identified nine LBD genes clustered with these reported adventitious root-related LBDs, but only three superlocus-associated LBD genes (PpBSBRL, PpSBRL1, and PpSBRL2) revealed significant upregulation in expression level during the induction phase of peach adventitious rooting. Functional analysis demonstrated that PpBSBRL, PpSBRL1, and PpSBRL2 positively regulate both lateral and adventitious root formation in peach seedlings. Further investigation established a direct interaction between PpBSBRL and PpSBRL2. Notably, PpBSBRL specifically binds to the promoter region of PpSBRL2 (-1021~-516 bp) and transcriptionally activates its expression. This study provides the first evidence of a regulatory mechanism between PpBSBRL and PpSBRL2 during adventitious root development, offering theoretical insights to address the challenge of poor rooting capacity in peach cuttings.