bZIP Transcription Factor PavbZIP6 Regulates Anthocyanin Accumulation by Increasing Abscisic Acid in Sweet Cherry

Basic leucine zipper (bZIP) transcription factors (TFs) play a crucial role in anthocyanin accumulation in plants. In addition to bZIP TFs, abscisic acid (ABA) increases anthocyanin biosynthesis. Therefore, this study aimed to investigate whether bZIP TFs are involved in ABA-induced anthocyanin accumulation in sweet cherry and elucidate the underlying molecular mechanisms. Specifically, the BLAST method was used to identify <i>bZIP</i> genes in sweet cherry. Additionally, we examined the expression of ABA- and anthocyanin-related genes in sweet cherry following the overexpression or knockdown of a <i>bZIP</i> candidate gene. In total, we identified 54 <i>bZIP</i>-encoding genes in the sweet cherry genome. <i>Basic leucine zipper 6</i> (<i>bZIP6</i>) showed significantly increased expression, along with increased anthocyanin accumulation in sweet cherry. Additionally, yeast one-hybrid and dual-luciferase assays indicated that PavbZIP6 enhanced the expression of anthocyanin biosynthetic genes (<i>PavDFR</i>, <i>PavANS</i>, and <i>PavUFGT</i>), thereby increasing anthocyanin accumulation. Moreover, PavbZIP6 interacted directly with the <i>PavBBX6</i> promoter, thereby regulating <i>PavNCED1</i> to promote abscisic acid (ABA) synthesis and enhance anthocyanin accumulation in sweet cherry fruit. Conclusively, this study reveals a novel mechanism by which <i>PavbZIP6</i> mediates anthocyanin biosynthesis in response to ABA and contributes to our understanding of the mechanism of <i>bZIP</i> genes in the regulation of anthocyanin biosynthesis in sweet cherry.