The apple 14-3-3 protein MdGRF11 interacts with the BTB protein MdBT2 to regulate nitrate deficiency-induced anthocyanin accumulation

Nitrogen is an important factor that affects plant anthocyanin accumulation.In apple,the nitrate-responsive BTB/TAZ protein MdBT2 negatively regulates anthocyanin biosynthesis.In this study,we found that MdBT2 undergoes posttranslational modifications in response to nitrate deficiency.Yeast two-hybrid,protein pull-down,and bimolecular fluorescence complementation(BiFC)assays showed that MdBT2 interacts with MdGRF11,a 14-3-3 protein;14-3-3 proteins compose a family of highly conserved phosphopeptide-binding proteins involved in multiple physiological and biological processes.The interaction of MdGRF11 negatively regulated the stability of the MdBT2 protein via a 26S proteasome-dependent pathway,which increased the abundance of MdMYB1 proteins to activate the expression of anthocyanin biosynthesis-related genes.Taken together,the results demonstrate the critical role of 14-3-3 proteins in the regulation of nitrate deficiency-induced anthocyanin accumulation.Our results provide a novel avenue to elucidate the mechanism underlying the induction of anthocyanin biosynthesis in response to nitrate deficiency.