Isolation and Role of PmRGL2 in GA-mediated Floral Bud Dormancy Release in Japanese Apricot (Prunus mume Siebold et Zucc.)

Abstract

Bud dormancy release is regulated by gibberellins (GAs). DELLA proteins are highly conserved and act as negative regulators in GA signaling pathway. The present study established a relationship between <i>PmRGL2</i> in Japanese apricot and GA₄ levels during dormancy release of floral buds. Overexpression of <i>PmRGL2</i> in poplar delayed the onset of bud dormancy and resulted in dwarf plants, relative to wild-type trees. <i>PmRGL2</i> exhibited higher expression during ecodormancy and relatively lower expression during endodormancy. The relative level of GA₄ exhibited an increasing trend at the transition from endodormancy to ecodormancy and displayed a similar expression pattern of genes related to GA metabolism, <i>PmGA20ox2</i>, <i>PmGA3ox1, PmGID1b</i>, in both Japanese apricot and transgenic poplar. These results suggests that <i>PmRGL2</i> acts as an integrator and negative regulator of dormancy via a GA-signaling pathway. Moreover, an interaction between <i>RGL2</i> and SLY1 in a yeast two hybrid (Y2H) system further suggests that SCF E3 ubiquitin ligases, such as <i>SLY1</i>, may be a critical factor in the regulation of <i>RGL2</i> through an SCF ^<i>SLY1</i> -proteasome pathway. Our study demonstrated that <i>PmRGL2</i> plays a negative role in bud dormancy release by regulating the GA biosynthetic enzymes, <i>GA20ox</i> and <i>GA3ox1</i> and the GA receptor, <i>GID1b</i>.