HY5 regulates anthocyanin biosynthesis by inducing the transcriptional activation of the MYB75/PAP1 transcription factor in <i>Arabidopsis</i>

Several positive transcription factors regulate Arabidopsis anthocyanin biosynthesis. HY5, a component of light-signaling pathways, and PAP1, an R2R3-MYB transcription factor, share common regulatory targets on anthocyanin biosynthesis genes. The epistatic interactions between the two transcription factors are currently unknown. To address this problem, we analyzed crosses between hy5 and pap1 mutants (hy5pap1) or pap1D overexpressors (hy5pap1D), performed chromatin immunoprecipitation-qPCR, and determined the PAP1 promoter region through deletion analysis. The results show that HY5 regulates PAP1 expression via direct binding to G- and ACE-boxes in the promoter region, which suggests bifurcate regulation of anthocyanin biosynthesis by HY5 via transcriptional activation of PAP1.