PsGA2ox2 is a novel target of miR159 involved in endodormancy regulation in tree peony (Paeonia suffruticosa)

Abstract In deciduous woody plants, buds enter endodormancy in late autumn, and endodormancy release (EDR) is a essential for regrowth. In tree peony, endodormancy is a major obstacle to forcing culture, an important component of its industry. Both chilling accumulation and gibberellin acid (GA) application can contribute to break dormancy and facilitate bud sprouting and flowering under appropriate conditions. PsmiR159b is one of the most abundant miRNAs in dormant buds, targeting PsMYB65 to inhibit bud EDR. Here, PsGA2ox2 was identified as a novel target of PsmiR159b according to expression data and genetic analysis. PsGA2ox2 expression was up-regulated by prolonged chilling, following with an increase of gibberellic acid 34 (GA 34 ), a product of deactivated GA 4 by GA2-oxidase. Silencing of PsGA2ox2 accelerated budbreak, accompanied by the increase of GA 1 and GA 4 , downregulation of PsABI5 , PsSVP , and upregulation of PsEBB1 , PsEBB3 , and PsCYCD . The content of GA 4 was downregulated in STTM159b buds, whereas increased in MIR159b-OE buds. In addition, the ectopic expression of PsGA2ox2 in Arabidopsis dramatically delayed seed germination and inhibited plant growth. These findings indicated a dual-target regulatory role for PsmiR159b in regulating GA homeostasis, and also revealed a PsmiR159b- PsGA2ox2 module that influenced EDR in tree peony through bioactive GA level regulation.