Genome-Wide Identification and Functional Characterization of QdA3oGT Genes Reveal a Molecular Mechanism of Autumnal Leaf Color Transition in Quercus dentata.

Autumnal leaf color transition is a crucial environmental adaptation strategy for trees. Quercus dentata is a typical autumn leaf tree species distributed in Northeast Asia, which is characterized by bright red leaves in autumn. However, the molecular mechanisms of leaf turning red respond to climatic factors are unclear. This study identified five anthocyanidin 3-O-glucosyltransferase (QdA3oGT) members, QdA3oGT2, with unique cis-elements, evolutionary background and gene structure, emerged as a key gene for leaf color transition. The transcript level of QdA3oGT2 was significantly higher than other members. qPCR revealed that the expression of QdA3oGT2 trend increased with leaf coloration, which was significantly positively correlated with anthocyanin content. Thus, QdA3oGT2 was identified as the key gene in leaf color transition of Q. dentata. Functional validation in Arabidopsis demonstrated that QdA3oGT2 was stimulated by low temperature, leading to enhanced cold resistance by anthocyanin accumulation. Furthermore, a cold-responsive and senescence-related transcription factor, QdNAC58 was identified, which directly bound to the NAC conserved binding motif 'ACGTCA' in QdA3oGT2 promoter, and positively regulated QdA3oGT2. In sum, this study reveals that QdNAC58, responds to low temperatures of autumn, further upregulates QdA3oGT2 to play a key role in anthocyanin synthesis associated with leaf senescence.