Evolution and functional diversification of R2R3-MYB transcription factors in plants

Abstract

R2R3-MYB genes (R2R3-MYBs) form one of the largest transcription factor gene families in the plant kingdom, with substantial structural and functional diversity. However, the evolutionary processes leading to this amazing functional diversity have not yet been clearly established. Recently developed genomic and classical molecular technologies have provided detailed insights into the evolutionary relationships and functions of plant R2R3-MYBs. Here, we review recent genome-level and functional analyses of plant R2R3-MYBs, with an emphasis on their evolution and functional diversification. In land plants, this gene family underwent a large expansion by whole genome duplications and small-scale duplications. Along with this population explosion, a series of functionally conserved or lineage-specific subfamilies/groups arose with roles in three major plant-specific biological processes: development and cell differentiation, specialized metabolism, and biotic and abiotic stresses. The rapid expansion and functional diversification of plant R2R3-MYBs are highly consistent with the increasing complexity of angiosperms. In particular, recently derived R2R3-MYBs with three highly homologous intron patterns (a, b, and c) are disproportionately related to specialized metabolism and have become the predominant subfamilies in land plant genomes. The evolution of plant R2R3-MYBs is an active area of research, and further studies are expected to improve our understanding of the evolution and functional diversification of this gene family.

The genomic and bulked segregant analysis of Curcuma alismatifolia revealed its diverse bract pigmentation

“…27 and Supplementary Tables 17 and 18). The subgroups of 4–7, 44, and 79 of MYB regulators (Wu et al 2022 ), IIIf, IIId + e, and IVd of bHLH regulators (Xie et al 2012 ; Zhao et al 2018 , 2019 , 2020 ) and WD40 protein TTG1 homologs (Baudry et al 2004 ; Belwal et al 2020 ; Gonzalez et al 2008 ) have been reported to be involved in anthocyanin synthesis; these most important subgroups of MYB , bHLH , and WD40 genes (Supplementary Figs. 28 and 29, Supplementary Table 19) were identified by a phylogenetic analysis based on homologs from A. thaliana and SG79 in other species (Wu et al 2022 ).…”

“…The biosynthesis of anthocyanins is catalyzed by several structural genes, such as chalcone synthase ( CHS ), and flavonoid-3′,5′-hydroxylase ( F3′5′H ), dihydroflavonol 4-reductase ( DFR ), and anthocyanidin synthase ( ANS ) (Belwal et al 2020 ; Harborne and Williams 2000 ; Mol et al 1998 ) and is also affected by transcription factors, such as MYB, bHLH, and WD40. Several subgroups of these transcription factors have been shown to be involved in anthocyanin synthesis, including subgroup 4–7, 44, and 79 of MYB regulators (Wu et al 2022 ), subgroup IIIf, IIId + e, and IVd of bHLH regulators (Xie et al 2012 ; Zhao et al 2018 , 2019 , 2020 ), and WD40 proteins TRANSPARENT TESTA GLABRA1 (TTG1) homologs (Baudry et al 2004 ; Belwal et al 2020 ; Gonzalez et al 2008 ). In the anthocyanin synthesis pathway of Arabidopsis , the MYB genes interact with the bHLH transcription factors and the WD40 protein family to form the MYB–bHLH–WD40 (MBW) complex to regulate the formation and accumulation of anthocyanins (Dubos et al 2010 ; Yan et al 2021 ).…”

MYB Transcription Factors Becoming Mainstream in Plant Roots

“…For example, the members of the 3R-MYB family in Arabidopsis play a similar role with their homologs in animals in cell cycle regulation [ 19 , 20 , 21 ]. On the contrary, the members of MYB-related and 2R-MYB families have diverse functions in many plant-specific processes [ 18 , 22 ]. To date, the major roles of MYB -related genes characterized are related to organ development, stress response, and circadian clock [ 18 ].…”

“…For example, CPC-like subfamily homologs are involved in cell fate determination [ 23 ], AtMYBL response to ABA and salt stresses [ 24 ], and AtCCA1 with its homologs are involved in circadian rhythm [ 18 ]. Consistent with its vast number and phylogenetic classification, the 2R-MYB family has diverse functions in plants, which can be briefly summarized into three major biological processes: development and cell differentiation, biotic and abiotic stresses, and specialized metabolism [ 22 ]. For instance, the genes in the S15 subfamily are associated with cell fate determination [ 10 ], the genes in the S22 subfamily respond to drought and pathogen invasion [ 25 ], and those in the S6 subfamily participate in anthocyanin biosynthesis [ 26 ], etc.…”

The Transcription Factor MYB37 Positively Regulates Photosynthetic Inhibition and Oxidative Damage in Arabidopsis Leaves Under Salt Stress

“…The MYB proteins are divided into four subfamilies based on the number of adjacent repeats in the MYB domain (R1-MYB, R2R3-MYB, 3R-MYB, and 4R-MYB; Dubos et al, 2010 ). The R2R3-MYB family is common in plants ( Jiang and Rao, 2020 ; Wu et al, 2022 ), with about 126 of these TFs found in Arabidopsis ( Chen et al, 2006 ). Many members of the MYB TF family participate in Arabidopsis response to salt stress ( Mengiste et al, 2003 ; Xie et al, 2010 ; Cui et al, 2013 ; Xu et al, 2015 ; Wang et al, 2016 ).…”