Molecular characterization of 60 isolated wheat MYB genes and analysis of their expression during abiotic stress

The proteins of the MYB superfamily play central roles in developmental processes and defence responses in plants. Sixty unique wheat MYB genes that contain full-length cDNA sequences were isolated. These 60 genes were grouped into three categories, namely one R1R2R3-MYB, 22 R2R3-MYBs, and 37 MYB-related members. The sequence composition of the R2 and R3 repeats was conserved among the 22 wheat R2R3-MYB proteins. Phylogenetic comparison of the members of this superfamily among wheat, rice, and Arabidopsis revealed that the putative functions of some wheat MYB proteins were clustered into the Arabidopsis functional clades. Tissue-specific expression profiles showed that most of the wheat MYB genes were expressed in all of the tissues examined, suggesting that wheat MYB genes take part in multiple cellular processes. The expression analysis during abiotic stress identified a group of MYB genes that respond to one or more stress treatments. The overexpression of a salt-inducible gene, TaMYB32, enhanced the tolerance to salt stress in transgenic Arabidopsis. This study is the first comprehensive study of the MYB gene family in Triticeae.     

拟南芥R2R3-MYB类转录因子在环境胁迫中的作用

MYB转录因子是植物转录因子中最大的家族之一,以含有保守的MYB结构域为共同特征,分为三个亚族（R1／2-MYB、R2R3-MYB和R1R2R3-MYB）,其中含有两个MYB结构域的R2R3-MYB成员最多,广泛参与植物次生代谢调控、细胞形态发生、胁迫应答、分生组织形成及细胞周期控制等。近年来,R2R3-MYB在植物逆境胁迫中的作用引起了广泛关注,本文综述了拟南芥R2R3-MYB蛋白在环境胁迫响应中作用的研究进展。     

Identification,isolation and expression analysis of eight stress-related <Emphasis Type="Italic">R2R3</Emphasis>-<Emphasis Type="Italic">MYB</Emphasis> genes in tartary buckwheat (<Emphasis Type="Italic">Fagopyrum tataricum</Emphasis>)

Key message

Eight R2R3 - MYB genes in tartary buckwheat were identified, and their expression patterns were comprehensively analyzed, which reveals role in plant response to abiotic stresses.

Abstract

The proteins of the R2R3-MYB superfamily play key roles in the growth and development processes as well as defense responses in plants. However, their characteristics and functions have not been fully investigated in tartary buckwheat (Fagopyrum tataricum), a strongly abiotic resistant coarse cereal. In this article, eight tartary buckwheat R2R3-MYB genes were isolated with full-length cDNA and DNA sequences. Phylogenetic analysis of the members of the R2R3-MYB superfamily between Arabidopsis and tartary buckwheat revealed that the assumed functions of the eight tartary buckwheat R2R3-MYB proteins are divided into five Arabidopsis functional subgroups that are involved in abiotic stress. Expression analysis during abiotic stress and exogenous phytohormone treatments identified that the eight R2R3-MYB genes responded to one or more treatments. This study is the first comprehensive analysis of the R2R3-MYB gene family in tartary buckwheat under abiotic stress.

     

杨树MYB转录因子家族基因应答盐胁迫表达特性分析

MYB转录因子家族是植物中数量最多的转录因子家族之一,在植物次生代谢调节、信号转导和抗逆等生物过程起重要作用。根据MYB转录因子结构域组成差异可分4个亚家族：即1R-MYB（MYB-relaed）、R2R3-MYB、3R-MYB和4R-MYB。其中,R2R3-MYB亚家族数量最多,可进一步分为22个亚组;利用生物信息学分析杨树MYB转录因子蛋白序列的保守结构域、系统发生、基因组定位、氨基酸组成和理化性质等;参照拟南芥MYB转录因子功能,预测杨树MYB转录因子功能;基于84K杨转录组测序和RT-qPCR分析,从301个杨树MYB转录因子基因中筛选出69个应答盐胁迫基因（P≤0.05）。其中,上调表达基因32个,下调表达基因37个。该研究可为进一步研究杨树MYB家族基因功能提供参考依据。     

The MIXTA-like Transcription factor MYB16 is a major regulator of cuticle formation in vegetative organs

Cuticle secreted on the surface of the epidermis of aerial organs protects plants from the external environment. We recently found that Arabidopsis MIXTA-like R2R3-MYB family members MYB16 and MYB106 regulate cuticle formation in reproductive organs and trichomes. However, the artificial miRNA (amiRNA)-mediated knockdown plants showed no clear phenotypic abnormality in vegetative tissues. In this study, we used RNA interference (RNAi) targeting MYB16 to produce plants with reduced expression of both MYB16 and MYB106. The rosette leaves of RNAi plants showed more severe permeable cuticle phenotypes than the myb106 mutants expressing the MYB16 amiRNA in the previous study. The RNAi plants also showed reduced expression of cuticle biosynthesis genes LACERATA and ECERIFERUM1. By contrast, expression of a gain-of-function MYB16 construct induced over-accumulation of waxy substances on leaves. These results suggest that MYB16 functions as a major regulator of cuticle formation in vegetative organs, in addition to its effect in reproductive organs and trichomes.     

c-MYB oncogene-like genes encoding three MYB repeats occur in all major plant lineages

Since the identification of the first plant MYB-like protein, the Zea mays factor C1, the number of MYB-related genes described has greatly increased. All of the more than 150 plant MYB-like proteins known so far contain either two or only one sequence-related helix-turn-helix motif in their DNA-binding domain. Animal c-MYB genes contain three such helix-turn-helix motif-encoding repeats (R1R2R3 class genes). It has therefore been concluded that R2R3-MYB genes are the plant equivalents of c-MYB and that there are significant differences in the basic structure of MYB genes of plants and animals. Here, we describe expressed R1R2R3-MYB genes from Physcomitrella patients++ and Arabidopsis thaliana, designated PpMYB3R-1 and AtMYB3R-1. The amino acid sequences of their DNA-binding domains show high similarity to those of animal MYB factors, and less similarity to R2R3-MYB proteins from plants. In addition, R1R2R3-MYB genes were identified in different plant evolutionary lineages including mosses, ferns and monocots. Our data show that a DNA-binding domain consisting of three MYB repeats existed before the divergence of the animal and plant lineages. R1R2R3-MYB genes may have a conserved function in eukaryotes, and R2R3-MYB genes may predominantly regulate plant-specific processes which evolved during plant speciation.