Functional MYB transcription factor encoding gene AN2 is associated with anthocyanin biosynthesis in Lycium ruthenicum Murray

Yuan Zong,Xuebing Zhu,Guomin Li,Jianming Li,Zenggen Liu,Le Wei,Baolong Liu,Xinyuan Xi,Dong Cao

doi:10.1186/s12870-019-1752-8

Abstract

BackgroundLycium ruthenicum Murray is an important economic plant in China and contains higher levels of anthocyanins in its fruits than other Lyciums. However, the genetic mechanism of anthocyanin production in this plant is unknown.ResultsBased on previous transcriptome analysis, LrAN2 and LbAN2, encoding MYB transcription factors, were isolated from L. ruthenicum and L. barbarum, respectively. Both genes contained two introns, encoded 257 amino acids with two-Aa difference, and carried the unabridged HTH-MYB, MYB-like DNA-binding, and SANT domains. In the phylogenetic trees, LrAN2 and LbAN2 were found to be closely related to NtAN2, which regulates anthocyanin biosynthesis in tobacco. Overexpression of LrAN2 and LbAN2 induced anthocyanin biosynthesis in all tissues of tobacco. The anthocyanin content in the leaves of transgenic lines with LbAN2 was lower than LrAN2. It indicated that the function of LbAN2 was weaker than LrAN2. The AN2 transcript could be detected only in the fruits of L. ruthenicum and increased during fruit development, accompanied by anthocyanin accumulation. In natural population, the alleles LrAN2 and LrAN2 were associated strictly with L. ruthenicum and L. barbarum, respectively. Moreover, an AN2 genetic diversity study suggested that Lyciums with yellow, white, purple, and jujube red fruits were derived from L. ruthenicum.ConclusionsTwo AN2 alleles, from L. ruthenicum and L. barbarum, were functional MYB transcriptor regulating anthocyanin biosynthesis. The functional diversity and high expression level of LrAN2 could be the reason for high anthocyanin content in the fruit of L. ruthenicum. Lyciums with yellow, white, purple, and jujube red fruits were derived from L. ruthenicum based on AN2 sequence diversity. The results may be advantageous in identifying new varieties and breeding new cultivars.

Highlights

Lycium ruthenicum Murray is an important economic plant in China and contains higher levels of anthocyanins in its fruits than other Lyciums
Molecules characteristics Previous experiments have shown that the expression of myeloblastosis viral oncogene homolog (MYB) transcription factor AN2 occurs at a higher level in fruits of L. ruthenicum than L. barbarum
LrAN2 and LbAN2 were isolated from L. ruthenicum and L. barbarum based on RNA-sequence data

Summary

Introduction

Lycium ruthenicum Murray is an important economic plant in China and contains higher levels of anthocyanins in its fruits than other Lyciums. The structural genes are regulated by transcription factors such as V-myb avian myeloblastosis viral oncogene homolog (MYB) and basic Helix-Loop-Helix (bHLH) [12]. The inactivation of any of these structural genes and transcription factors blocks the metabolic pathway, causing plant tissues to display a pale phenotype [13]. Allelic variations in the MYB and bHLH genes more commonly cause colour differentiation in plants. The bHLH genes R, B, Sn and Hopi from maize could induce tissue-specific anthocyanin biosynthesis in maize, including expression in the aleurone, pericarp, anther, mesocotyl, root, leaf, and scutellum [20,21,22,23,24]. Homologues of maize R and B genes were found in Antirrhinum (Delila) [26], petunia (Jaf13) [27], and tomato (ah) [28]

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