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

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

doi:10.3389/fpls.2021.688707

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

Front Plant Sci. 2021 Sep 23:12:688707. doi: 10.3389/fpls.2021.688707. eCollection 2021.

Authors

Daowei Zhang^{1

2}, Yongjun Tan³, Fang Dong², Ya Zhang², Yanlan Huang², Yizhou Zhou², ZhiJian Zhao⁴, Qin Yin², Xuehua Xie², Xiewang Gao², Chaofan Zhang², Naimei Tu¹

Affiliations

¹ College of Agronomy, Hunan Agricultural University, Changsha, China.
² Crop Research Institute, Hunan Academy of Agricultural Sciences, Changsha, China.
³ Department of Biology, School of Life Sciences, Southern University of Science and Technology, Shenzhen, China.
⁴ Dryland Crop Research Institute, Shao Yang Academy of Agriculture Science, Shaoyang, China.

Abstract

IbMYB1 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, IbMYB1-1, -2a, and -2b, have been reported. We found that IbMYB1-2a and -2b 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 IbMYB1 is essential to maintain the purple color of leaves and storage roots in this type of cultivated species, which did not contain IbMYB1-2 gene members. Compared with IbbHLH2, IbMYB1 is an early response gene of anthocyanin biosynthesis in sweet potato. It cannot exclude the possibility that other MYBs participate in this gene regulation networks. Twenty-two MYB-like genes were identified from 156 MYBs to be highly positively or negatively correlated with the anthocyanin content in leaves or flesh. Even so, the IbMYB1 was most coordinately expressed with anthocyanin biosynthesis genes. Differences in flanking and coding sequences confirm that IbMYB2s, the highest similarity genes of IbMYB1, are not the members of IbMYB1. This phenomenon indicates that there may be more members of IbMYB1 in sweet potato, and the genetic complementation of these members is involved in the regulation of anthocyanin biosynthesis. The 3' flanking sequence of IbMYB1-1 is homologous to the retrotransposon sequence of TNT1-94. Transposon movement is involved in the formation of multiple members of IbMYB1. This study provides critical insights into the expression patterns of IbMYB1, 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 IbMYB1 for genetic improvement.

Keywords: R2R3-MYB; anthocyanin biosynthesis; early response gene; multiple members; purple-fleshed sweetpotato; transcriptome.