Auxin response factor, RhARF8 contributes to rose flower color fading via regulating anthocyanin biosynthesis by directly activating <i>RhCHSa</i>/<i>c</i> promoter activity

Petal color is one of the most important agricultural traits in rose plants. However, the relationship between petal coloration and hormones remain largely unknown. Our research revealed that auxin (IAA) is essential for anthocyanin biosynthesis and the prevention of color fading in rose petals. Meanwhile, <italic>RhARF1</italic>/<italic>8</italic> expression levels were significantly induced by IAA treatment. Yeast one-hybrid (Y1H), dual-luciferase assays, and chromatin immunoprecipitation of quantitative PCR (ChIP-qPCR) demonstrated that RhARF8 could bind to promoters of anthocyanin biosynthesis genes <italic>RhCHSa/c</italic> (specifically the P3 fragment of the <italic>RhCHSa</italic> promoter and the P1 fragment of the <italic>RhCHSc</italic> promoter) and activates their promoter activities, whereas RhARF1 could not. In addition, silencing or overexpression of <italic>RhARF8</italic> showed that IAA prolonged petal color retention and delayed petal senescence by mediating the <italic>RhARF8</italic> expression. In conclusion, our study identifies an auxin signaling factor, RhARF8, which acts as a key regulator of anthocyanin biosynthesis in rose petals via regulating the anthocyanin biosynthesis genes <italic>RhCHSa/c</italic>. These findings provide a theoretical basis for improving rose petal color traits through breeding or genetic engineering.