Genome-wide identification of the PpSWEET gene family and function characterization of PpSWEET6 associated with endodormancy release in peach bud

Bud endodormancy represents an ecological adaptation mechanism in perennial deciduous fruit trees to endure winter cold conditions. Sucrose serves a crucial role in bud endodormancy as both an energy metabolizer and signaling molecule. Sugars Will Eventually be Exported Transporters (SWEETs) function as sugar-efflux transporters that respond to environmental stimuli and contribute to plant growth and development. While SWEET gene families have been identified in various plant species for sugar transport regulation, their mechanism in regulating peach bud endodormancy remains undefined. In this study, we identified 15 SWEET genes in peach. The nomenclature was established through homologous alignment with the Arabidopsis SWEET gene family, resulting in four distinct clades through phylogenetic analysis. Covariance correlation analysis revealed 6 and 12 collinear SWEET genes in peach and Arabidopsis, respectively, forming 13 collinear gene pairs. Real-time quantitative polymerase chain reaction (RT-qPCR) analysis demonstrated significantly elevated expression of PpSWEET6 during peach bud endodormancy release, correlating positively with sucrose content. Transient overexpression of PpSWEET6 enhanced peach bud endodormancy release, while overexpressing PpSWEET6 in Arabidopsis enhanced seed germination and flowering. Y2H and luciferase complementation imaging (LCI) assays confirmed PpSWEET6 interacted with PpABF2. Additionally, dual luciferase reporter (DLR) assays showed that PpSWEET6 significantly decreased the activation of PpDAM6 (key dormancy-inducing gene) through PpABF2, thereby modulating peach bud endodormancy release. These findings advance our understanding of SWEET genes in peach bud endodormancy regulation.