Abstract
Bud dormancy is an adaptive mechanism that allows plant meristems to survive to the low temperatures of winter. In temperate fruit trees, such as apples (Malus domestica Borkh.), a well-adjusted dormancy cycle is crucial for the achievement of their full yield potential. Recently, it has been suggested that genes encoding Dormancy-Associated MADS-box (DAM) and flowering-time related MADS transcription factors (TF) regulate dormancy. DAM genes are similar to SHORT VEGETATIVE PHASE (SVP), which encodes a MADS TF that represses flowering in Arabidopsis thaliana. We previously isolated protein complexes formed between MdDAM and other dormancy related MADS TFs (MdFLC-like and MdSVP-like) and defined their transcriptional genome-wide targets. The present work aims to further characterize apple MADS transcription factors potentially involved in dormancy control. We first identified common target genes between apple SVP-like TF and the Arabidopsis SVP and found that 24 genes are directly regulated by SVP-like TFs in both species. Notably, several of these target genes are related to flowering and dormancy, including MdSOC1a, an apple homolog of the Arabidopsis gene SUPPRESSOR OF OVEREXPRESSION OF CONSTANS 1 (SOC1). Furthermore, we found that the SOC1-like TFs MdSOC1a and MdSOC1b physically interact with several dormancy related MADS TFs. Finally, based on the mRNA expression pattern of MdSOC1a and MdSOC1b, we proposed that the proteins that they encode are part of transcriptional complexes involved in the control of dormancy cycle in fruit trees.