Mining MYB transcription factors from the genomes of orchids (Phalaenopsis and Dendrobium) and characterization of an orchid R2R3-MYB gene involved in water-soluble polysaccharide biosynthesis

Chunmei He,Can Si,Jaime A Teixeira Da Silva,Jun Duan,Jianwen Tan,Xiaoming Zhang,Mingze Zhang,Mingzhi Li,Haobin Wang

doi:10.1038/s41598-019-49812-8

Abstract

Members of the MYB superfamily act as regulators in a wide range of biological processes in plants. Despite this, the MYB superfamily from the Orchidaceae has not been identified, and MYB genes related to bioactive water-soluble polysaccharide (WSP) biosynthesis are relatively unknown. In this study, we identified 159 and 165 MYB genes from two orchids, Phalaenopsis equestris and Dendrobium officinale, respectively. The MYB proteins were classified into four MYB classes in both orchids: MYB-related (MYBR), R2R3-MYB, 3R-MYB and atypical MYB proteins. The MYBR proteins in both orchids were classified into five subfamilies and 12 genes were strongly up-regulated in response to cold stress in D. officinale. The R2R3-MYB proteins were both divided into 31 clades in P. equestris and D. officinale. Among these clades, nine contained MYB TFs related to secondary cell wall biosynthesis or testa mucilage biosynthesis in Arabidopsis thaliana. In D. officinale, 10 candidate genes showed an expression pattern corresponding to changes in the WSP content. Overexpression of one of these candidate genes (DoMYB75) in A. thaliana increased seed WSP content by about 14%. This study provides information about MYB genes in two orchids that will further help to understand the transcriptional regulation of WSP biosynthesis in these orchids as well as other plant species.

Highlights

Gene expression is regulated by various complex mechanisms, including modifications to DNA such as histone modification and DNA methylation, as well as various RNA-mediated processes
A total of 159 and 165 MYB Transcription factors (TFs) were identified in two orchids, P. equestris and D. officinale, respectively
A similar number of MYB TF family members was found in D. officinale: 42 MYBR genes, 117 R2R3-MYB genes, four 3R-MYB genes and two atypical MYB genes were identified in the D. officinale genome (Table 1)

Summary

Introduction

Gene expression is regulated by various complex mechanisms, including modifications to DNA such as histone modification and DNA methylation, as well as various RNA-mediated processes. Over the past two decades, the R2R3-MYB TFs have been extensively exploited and many R2R3-MYB proteins have been shown to play roles in several biological processes, such as development, response to biotic and abiotic stresses, and metabolism[15,17]. Previous studies have demonstrated that R2R3-MYB genes, such as AtMYB5 and AtMYB61, are required for the production of seed mucilage, and the polysaccharide content of seed mucilage in the A. thaliana myb[61] mutant was significantly reduced[25,26]. These results indicate that R2R3-MYB members play roles in the biosynthesis of plant polysaccharides

Methods

Results

Conclusion