A DNA demethylase overexpression promotes early apical bud maturation in poplar through the biosynthesis and accumulation of flavonoids

Abstract

ASBTRACTThe transition from active growth to dormancy is critical for the survival of perennial plants. We identified a DEMETER-like (CsDML) cDNA from a winter-enriched cDNA subtractive library in chestnut (Castanea sativa Mill.), an economically and ecologically important species. Next, we characterized this DNA demethylase and its putative orthologue in the more experimentally tractable hybrid poplar (Populus tremula x alba), under the signals that trigger bud dormancy in trees. We performed phylogenetic and protein sequence analysis, gene expression profiling and 5mC immunodetection studies to evaluate the role of CsDML and its homologue in poplar, PtaDML6. Transgenic hybrid poplars overexpressing CsDML were produced and analyzed. Short days (SD) and cold temperatures induced CsDML and PtaDML6. Overexpression of CsDML accelerated SD-induced bud formation, specifically from stage 1 to 0. Bud acquired a red-brown coloration earlier than wild type (WT) plants, alongside with the upregulation of flavonoid biosynthesis enzymes and accumulation of flavonoids in the SAM and bud scales. Our data shows that the CsDML gene induces bud formation needed for the survival of the apical meristem under the harsh conditions of winter. This study provides in planta evidence implicating chromatin remodeling by DNA demethylation during SD induction of bud maturation through the induction of flavonoids biosynthesis.