AUTHOR=Qian Jieyu , Jiang Lingli , Qing Hongsheng , Chen Jiahong , Wan Ziyun , Xu Menghan , Fu Jianxin , Zhang Chao 

TITLE=ZeMYB9 regulates cyanidin synthesis by activating the expression of flavonoid 3′-hydroxylase gene in Zinnia elegans

JOURNAL=Frontiers in Plant Science

VOLUME=13

YEAR=2022

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2022.981086

DOI=10.3389/fpls.2022.981086

ISSN=1664-462X

ABSTRACT=<p>Petal color in <italic>Zinnia elegans</italic> is characterized mainly by anthocyanin accumulation. The difference in the content of anthocyanins, especially cyanidins, affects petal coloration in <italic>Z. elegans</italic>, but the underlying regulatory mechanism remains elusive. Here, we report one R2R3-MYB transcription factor from subgroup 6, ZeMYB9, acting as a positive regulator of anthocyanin accumulation in <italic>Z. elegans</italic>. Up-regulated expression of <italic>ZeMYB9</italic> and flavonoid 3′-hydroxylase gene (<italic>ZeF3’H</italic>) was detected in the cultivar with higher cyanidin content. ZeMYB9 could specifically activate the promoter of <italic>ZeF3’H</italic>, and over-expression of <italic>ZeMYB9</italic> induces much greater anthocyanin accumulation and higher expression level of anthocyanin biosynthetic genes in both petunia and tobacco. And then, ZeMYB9 was demonstrated to interact with ZeGL3, a bHLH transcription factor belonging to IIIf subgroup. Promoter activity of <italic>ZeF3’H</italic> was significantly promoted by co-expressing <italic>ZeMYB9</italic> and <italic>ZeGL3</italic> compared with expressing <italic>ZeMYB9</italic> alone. Moreover, transient co-expression of <italic>ZeMYB9</italic> and <italic>ZeGL3</italic> induced anthocyanin accumulation in tobacco leaves. Our results suggest that ZeMYB9 could enhance cyanidin synthesis and regulate petal color in <italic>Z. elegans</italic> though activating the expression of <italic>ZeF3’H</italic>, by itself or interacting with ZeGL3.</p>