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Regulation of anthocyanin and proanthocyanidin biosynthesis by M edicago truncatula b HLH transcription factor M t TT 8
Author(s) -
Li Penghui,
Chen Beibei,
Zhang Gaoyang,
Chen Longxiang,
Dong Qiang,
Wen Jiangqi,
Mysore Kirankumar S.,
Zhao Jian
Publication year - 2016
Publication title -
new phytologist
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.742
H-Index - 244
eISSN - 1469-8137
pISSN - 0028-646X
DOI - 10.1111/nph.13816
Subject(s) - mutant , myb , anthocyanidin , medicago truncatula , biology , biochemistry , anthocyanin , biosynthesis , transcription factor , ectopic expression , chemistry , microbiology and biotechnology , gene , botany , genetics , symbiosis , bacteria
Summary The MYB ‐ basic helix–loop–helix ( bHLH )‐ WD 40 complexes regulating anthocyanin and proanthocyanidin ( PA ) biosynthesis in plants are not fully understood. Here Medicago truncatula bHLH Mt TT 8 was characterized as a central component of these ternary complexes that control anthocyanin and PA biosynthesis. Mttt8 mutant seeds have a transparent testa phenotype with reduced PA s and anthocyanins. Mt TT 8 restores PA and anthocyanin productions in Arabidopsis tt8 mutant. Ectopic expression of Mt TT 8 restores anthocyanins and PA s in mttt8 plant and hairy roots and further enhances both productions in wild‐type hairy roots. Transcriptomic analyses and metabolite profiling of mttt8 mutant seeds and M. truncatula hairy roots ( mttt8 mutant, mttt8 mutant complemented with Mt TT 8 , or Mt TT 8 overexpression lines) indicate that Mt TT 8 regulates a subset of genes involved in PA and anthocyanin biosynthesis. Mt TT 8 is genetically regulated by Mt LAP 1, Mt PAR and Mt WD 40‐1. Combinations of Mt PAR , Mt LAP 1, Mt TT 8 and Mt WD 40‐1 activate Mt TT 8 promoter in yeast assay. Mt TT 8 interacts with these transcription factors to form regulatory complexes. Mt TT 8, Mt WD 40‐1 and an MYB factor, Mt PAR or Mt LAP 1, interacted and activated promoters of anthocyanidin reductase and anthocyanidin synthase to regulate PA and anthocyanin biosynthesis, respectively. Our results provide new insights into the complex regulation of PA and anthocyanin biosynthesis in M. truncatula .