AUTHOR=Zhang Daowei , Tan Yongjun , Dong Fang , Zhang Ya , Huang Yanlan , Zhou Yizhou , Zhao ZhiJian , Yin Qin , Xie Xuehua , Gao Xiewang , Zhang Chaofan , Tu Naimei 

TITLE=The Expression of IbMYB1 Is Essential to Maintain the Purple Color of Leaf and Storage Root in Sweet Potato [Ipomoea batatas (L.) Lam]

JOURNAL=Frontiers in Plant Science

VOLUME=12

YEAR=2021

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2021.688707

DOI=10.3389/fpls.2021.688707

ISSN=1664-462X

ABSTRACT=<p><italic>IbMYB1</italic> was one of the major anthocyanin biosynthesis regulatory genes that has been identified and utilized in purple-fleshed sweet potato breeding. At least three members of this gene, namely, <italic>IbMYB1-1</italic>, <italic>-2a</italic>, and <italic>-2b</italic>, have been reported. We found that <italic>IbMYB1-2a</italic> and <italic>-2b</italic> are not necessary for anthocyanin accumulation in a variety of cultivated species (hexaploid) with purple shoots or purplish rings/spots of flesh. Transcriptomic and quantitative reverse transcription PCR (RT-qPCR) analyses revealed that persistent and vigorous expression of <italic>IbMYB1</italic> is essential to maintain the purple color of leaves and storage roots in this type of cultivated species, which did not contain <italic>IbMYB1-2</italic> gene members. Compared with <italic>IbbHLH2</italic>, <italic>IbMYB1</italic> is an early response gene of anthocyanin biosynthesis in sweet potato. It cannot exclude the possibility that other <italic>MYBs</italic> participate in this gene regulation networks. Twenty-two <italic>MYB-like</italic> genes were identified from 156 <italic>MYBs</italic> to be highly positively or negatively correlated with the anthocyanin content in leaves or flesh. Even so, the <italic>IbMYB1</italic> was most coordinately expressed with anthocyanin biosynthesis genes. Differences in flanking and coding sequences confirm that <italic>IbMYB2s</italic>, the highest similarity genes of <italic>IbMYB1</italic>, are not the members of <italic>IbMYB1</italic>. This phenomenon indicates that there may be more members of <italic>IbMYB1</italic> in sweet potato, and the genetic complementation of these members is involved in the regulation of anthocyanin biosynthesis. The 3′ flanking sequence of <italic>IbMYB1-1</italic> is homologous to the retrotransposon sequence of <italic>TNT1-94</italic>. Transposon movement is involved in the formation of multiple members of <italic>IbMYB1</italic>. This study provides critical insights into the expression patterns of <italic>IbMYB1</italic>, which are involved in the regulation of anthocyanin biosynthesis in the leaf and storage root. Notably, our study also emphasized the presence of a multiple member of <italic>IbMYB1</italic> for genetic improvement.</p>