Molecular regulation of winter bud dormancy in mulberry (Morus spp.) through the MaSVP-MaBGA signaling module

Maintenance of winter bud dormancy is a critical agronomic trait determining the fruit ripening period in mulberry (Morus spp.); however, the underlying molecular regulatory mechanisms remain largely elusive. In this study, we utilized an F1 segregating population derived from a cross between the late-budding species Morus wittiorum and the early-budding cultivar '322'. By integrating bulked segregant analysis sequencing (BSA-Seq) with RNA-Seq, we identified a dormancy-associated quantitative trait locus (QTL) interval (LB, 9.99-11.99 Mb) on chromosome 13 and pinpointed MaBGA (a β-glucosidase gene) as a candidate gene. Functional characterization via virus-induced gene silencing (VIGS) demonstrated that MaSVP acts as a repressor of winter bud sprouting, whereas MaBGA facilitates dormancy release. Yeast one-hybrid, dual-luciferase reporter, and electrophoretic mobility shift assays (EMSA) further confirmed that MaSVP directly binds to the MaBGA promoter to repress its transcription. Consistently, MaBGA expression was significantly upregulated during bud sprouting. Here, we unveil a novel MaSVP-MaBGA regulatory module. Distinct from the classical model where SVP/DAM proteins regulate dormancy indirectly via hormone homeostasis, this module maintains winter bud dormancy through the direct molecular interaction between a transcription factor and a β-glucosidase gene, thereby expanding the molecular regulatory network of bud dormancy in perennial plants. These findings not only provide fresh insights into the dormancy mechanisms of mulberry but also offer critical genetic resources and theoretical foundations for the molecular breeding of early- and late-ripening varieties.