PlOBP1/PlDAM-PlSOC1 Module Regulates Bud Dormancy Transition in Response to Low Temperature.

The transition from bud endodormancy to ecodormancy is triggered by environmental cues, particularly low temperatures. However, the mechanism underlying bud dormancy transition (BDT) is largely unknown. Here, we identified a low-temperature-responsive, MADS-box family SUPPRESSOR OF OVEREXPRESSION OF CO1 (PlSOC1) under both natural and controlled low temperatures, which promotes BDT and confers low chilling requirement trait of herbaceous peony (Paeonia lactiflora). A novel transcription factor, DNA-binding One Zinc Finger (DOF) family OBF BINDING PROTEIN 1 (PlOBP1), was found to bind the AAAAG motif in the PlSOC1 promoter, acting as a negative regulator of BDT. PlOBP1 acts together with Dormancy Associated MADS-box (PlDAM) protein to enhance the transinhibitory effect of PlSOC1. Further gibberellic acid (GA) treatment showed that exogenous GA can replace long-term chilling to promote BDT, likely by inhibiting the expression of PlOBP1 while inducing the expression of PlSOC1. The elevated PlSOC1 forms a complex with PlDAM and inhibits PlDAM activity, further releasing the inhibition on PlSOC1, thereby amplifying PlSOC1 and triggering BDT. Our findings provide mechanistic insights into low-temperature-mediated GA regulation of BDT and reveal a novel role of DOF protein PlOBP1 and its interactions with MADS-box family members in bud dormancy regulation.