Transcription factor PyHY5 binds to the promoters of PyWD40 and PyMYB10 and regulates its expression in red pear ‘Yunhongli No. 1’

'Yunhongli No. 1' is a rare and well-colored red pear (Pyrus pyrifolia) germplasm resource, and is popular in the market due to its bright red color and high quality. Light induces the expression of transportation factor genes MYB10, WD40, and HY5, which then activate the expression of critical genes in the anthocyanin biosynthesis pathway to promote the synthesis and accumulation of anthocyanin, thus giving the red coloration. Protein HY5 is considered to be a key regulator for induction of anthocyanin biosynthesis. The MYB10 genes physically interact with HY5 to positively regulate anthocyanin biosynthesis in Arabidopsis, apple, and pear by binding to G-box motifs. However, how these transcription factors are regulated by sunlight remains unclear in 'Yunhongli No. 1'. In this study, the transcription factor PyHY5 was cloned, and subcellular localization assay showed that PyHY5 was distributed in the nucleus. The DNA fragments of PyHY5 had a typical BRLZ domain of the bZIP family, and then were aligned against the promoter sequences of PyMYB10 and PyWD40. Electrophoretic mobility shift and transient expression assays showed that PyHY5 could directly recognize and bind to the G-box motifs in the promoters of PyMYB10 and PyWD40, and so boosted transcriptional activation by co-expression. The results demonstrated that PyHY5 binding to G-box motifs of the promoters of PyMYB10 and PyWD40, enhanced its expression, and then promoted accumulation of anthocyanin in red 'Yunhongli No. 1'.