title: Ectopic Expression of the Coleus R2R3 MYB-Type Proanthocyanidin Regulator Gene SsMYB3 Alters the Flower Color in Transgenic Tobacco.
abstract: Proanthocyanidins (PAs) play an important role in plant disease defense and have beneficial effects on human health. We isolated and characterized a novel R2R3 MYB-type PA-regulator SsMYB3 from a well-known ornamental plant, coleus (Solenostemon scutellarioides), to study the molecular regulation of PAs and to engineer PAs biosynthesis. The expression level of SsMYB3 was correlated with condensed tannins contents in various coleus tissues and was induced by wounding and light. A complementation test in the Arabidopsis tt2 mutant showed that SsMYB3 could restore the PA-deficient seed coat phenotype and activated expression of the PA-specific gene ANR and two related genes, DFR and ANS. In yeast two-hybrid assays, SsMYB3 interacted with the Arabidopsis AtTT8 and AtTTG1 to reform the ternary transcriptional complex, and also interacted with two tobacco bHLH proteins (NtAn1a and NtJAF13-1) and a WD40 protein, NtAn11-1. Ectopic overexpression of SsMYB3 in transgenic tobacco led to almost-white flowers by greatly reducing anthocyanin levels and enhancing accumulation of condensed tannins. This overexpression of SsMYB3 upregulated the key PA genes (NtLAR and NtANR) and late anthocyanin structural genes (NtDFR and NtANS), but downregulated the expression of the final anthocyanin gene NtUFGT. The formative SsMYB3-complex represses anthocyanin accumulation by directly suppressing the expression of the final anthocyanin structural gene NtUFGT, through competitive inhibition or destabilization of the endogenous NtAn2-complex formation. These results suggested that SsMYB3 may form a transcription activation complex to regulate PA biosynthesis in the Arabidopsis tt2 mutant and transgenic tobacco. Our findings suggest that SsMYB3 is involved in the regulation of PA biosynthesis in coleus and has the potential as a molecular tool for manipulating biosynthesis of PAs in fruits and other crops using metabolic engineering.
authors.affiliation: State Key Laboratory for Conservation and Utilization of Subtropical Agro-bioresources, College of Life Sciences, South China Agricultural University, Guangzhou 510642, China.
authors.forename: Qinlong
authors.initials: Q
authors.lastname: Zhu
authors.affiliation: Chongqing Engineering Research Center for Floriculture, College of Horticulture and Landscape, Southwest University, Chongqing 400716, China.
authors.forename: Shunzhao
authors.initials: S
authors.lastname: Sui
authors.affiliation: Department of Botany, Chongqing Agricultural School, Chongqing 401329, China.
authors.forename: Xinghua
authors.initials: X
authors.lastname: Lei
authors.affiliation: State Key Laboratory for Conservation and Utilization of Subtropical Agro-bioresources, College of Life Sciences, South China Agricultural University, Guangzhou 510642, China.
authors.forename: Zhongfang
authors.initials: Z
authors.lastname: Yang
authors.affiliation: Chongqing Engineering Research Center for Rapeseed, College of Agronomy and Biotechnology, Southwest University, Chongqing 400716, China.
authors.forename: Kun
authors.initials: K
authors.lastname: Lu
authors.affiliation: ChongqingAgricultural Broadcasting and Television School, Chongqing 401121, China.
authors.forename: Guangde
authors.initials: G
authors.lastname: Liu
authors.affiliation: State Key Laboratory for Conservation and Utilization of Subtropical Agro-bioresources, College of Life Sciences, South China Agricultural University, Guangzhou 510642, China.
authors.forename: Yao-Guang
authors.initials: YG
authors.lastname: Liu
authors.affiliation: Chongqing Engineering Research Center for Floriculture, College of Horticulture and Landscape, Southwest University, Chongqing 400716, China.
authors.forename: Mingyang
authors.initials: M
authors.lastname: Li
mesh_terms: D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000235:genetics / Q000378:metabolism; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism; D051792:Basic Helix-Loop-Helix Proteins / Q000235:genetics / Q000378:metabolism; D003001:Cloning, Molecular; D031330:Coleus / Q000235:genetics*; D000066630:Ectopic Gene Expression; D035264:Flowers / Q000235:genetics; D008969:Molecular Sequence Data; D010802:Phylogeny; D010858:Pigmentation / Q000235:genetics*; D018515:Plant Leaves / Q000235:genetics; D010940:Plant Proteins / Q000145:classification / Q000235:genetics* / Q000378:metabolism; D030821:Plants, Genetically Modified / Q000235:genetics; D044945:Proanthocyanidins / Q000032:analysis / Q000378:metabolism*; D016415:Sequence Alignment; D013056:Spectrophotometry, Ultraviolet; D014026:Nicotiana / Q000235:genetics*
chemical_list: D029681:Arabidopsis Proteins; D051792:Basic Helix-Loop-Helix Proteins; D010940:Plant Proteins; D044945:Proanthocyanidins; C013221:proanthocyanidin