title: The Transcriptional Repressor MYB2 Regulates Both Spatial and Temporal Patterns of Proanthocyandin and Anthocyanin Pigmentation in Medicago truncatula.
abstract: Accumulation of anthocyanins and proanthocyanidins (PAs) is limited to specific cell types and developmental stages, but little is known about how antagonistically acting transcriptional regulators work together to determine temporal and spatial patterning of pigmentation at the cellular level, especially for PAs. Here, we characterize MYB2, a transcriptional repressor regulating both anthocyanin and PA biosynthesis in the model legume Medicago truncatula. MYB2 was strongly upregulated by MYB5, a major regulator of PA biosynthesis in M. truncatula and a component of MYB-basic helix loop helix-WD40 (MBW) activator complexes. Overexpression of MYB2 abolished anthocyanin and PA accumulation in M. truncatula hairy roots and Arabidopsis thaliana seeds, respectively. Anthocyanin deposition was expanded in myb2 mutant seedlings and flowers accompanied by increased anthocyanin content. PA mainly accumulated in the epidermal layer derived from the outer integument in the M. truncatula seed coat, starting from the hilum area. The area of PA accumulation and ANTHOCYANIDIN REDUCTASE expression was expanded into the seed body at the early stage of seed development in the myb2 mutant. Genetic, biochemical, and cell biological evidence suggests that MYB2 functions as part of a multidimensional regulatory network to define the temporal and spatial pattern of anthocyanin and PA accumulation linked to developmental processes.
authors.affiliation: Department of Biological Sciences, University of North Texas, Denton, Texas 76203-5017.
authors.forename: Ji Hyung
authors.identifier: http://orcid.org/0000-0002-2563-4144
authors.initials: JH
authors.lastname: Jun
authors.affiliation: Department of Biological Sciences, University of North Texas, Denton, Texas 76203-5017.
authors.forename: Chenggang
authors.identifier: http://orcid.org/0000-0002-0576-8567
authors.initials: C
authors.lastname: Liu
authors.affiliation: Department of Biological Sciences, University of North Texas, Denton, Texas 76203-5017.
authors.forename: Xirong
authors.identifier: http://orcid.org/0000-0002-1785-6417
authors.initials: X
authors.lastname: Xiao
authors.affiliation: Department of Biological Sciences, University of North Texas, Denton, Texas 76203-5017 richard.dixon@unt.edu.
authors.forename: Richard A
authors.identifier: http://orcid.org/0000-0001-8393-9408
authors.initials: RA
authors.lastname: Dixon
mesh_terms: D000872:Anthocyanins / Q000378:metabolism*; D017360:Arabidopsis / Q000166:cytology / Q000235:genetics / Q000378:metabolism; D035264:Flowers / Q000166:cytology / Q000235:genetics / Q000378:metabolism; D015870:Gene Expression; D018506:Gene Expression Regulation, Plant; D046913:Medicago truncatula / Q000166:cytology / Q000235:genetics* / Q000378:metabolism; D009154:Mutation; D010088:Oxidoreductases / Q000235:genetics / Q000378:metabolism; D010802:Phylogeny; D010858:Pigmentation; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism; D018517:Plant Roots / Q000166:cytology / Q000235:genetics / Q000378:metabolism; D030821:Plants, Genetically Modified; D044945:Proanthocyanidins / Q000378:metabolism*; D036226:Seedlings / Q000166:cytology / Q000235:genetics / Q000378:metabolism; D012639:Seeds / Q000166:cytology / Q000235:genetics / Q000378:metabolism; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*
chemical_list: D000872:Anthocyanins; D010940:Plant Proteins; D044945:Proanthocyanidins; D014157:Transcription Factors; D010088:Oxidoreductases