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Identification and characterization of MYB ‐b HLH ‐ WD 40 regulatory complexes controlling proanthocyanidin biosynthesis in strawberry ( F ragaria × ananassa ) fruits
Author(s) -
Schaart Jan G.,
Dubos Christian,
Romero De La Fuente Irene,
Houwelingen Adèle M. M. L.,
Vos Ric C. H.,
Jonker Harry H.,
Xu Wenjia,
Routaboul JeanMarc,
Lepiniec Loïc,
Bovy Arnaud G.
Publication year - 2013
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.12017
Subject(s) - transcriptome , proanthocyanidin , biology , myb , gene , biochemistry , gene expression , polyphenol , antioxidant
Summary Strawberry ( F ragaria × ananassa ) fruits contain high concentrations of flavonoids. In unripe strawberries, the flavonoids are mainly represented by proanthocyanidins ( PA s), while in ripe fruits the red‐coloured anthocyanins also accumulate. Most of the structural genes leading to PA biosynthesis in strawberry have been characterized, but no information is available on their transcriptional regulation. In A rabidopsis thaliana the expression of the PA biosynthetic genes is specifically induced by a ternary protein complex, composed of A t TT 2 ( A t MYB 123), A t TT 8 ( A tb HLH 042) and A t TTG 1 ( WD 40‐repeat protein). A strategy combining yeast‐two‐hybrid screening and agglomerative hierarchical clustering of transcriptomic and metabolomic data was undertaken to identify strawberry PA regulators. Among the candidate genes isolated, four were similar to AtTT2 , AtTT8 and AtTTG1 ( FaMYB9 / FaMYB11 , FabHLH3 and FaTTG1 , respectively) and two encode putative negative regulators ( FaMYB5 and FabHLH3∆ ). Interestingly, FaMYB9 / FaMYB11 , FabHLH3 and FaTTG1 were found to complement the tt2‐1 , tt8‐3 and ttg1‐1 transparent testa mutants, respectively. In addition, they interacted in yeast and activated the A rabidopsis BANYULS (anthocyanidin reductase) gene promoter when coexpressed in P hyscomitrella patens protoplasts. Taken together, these results demonstrated that FaMYB9 / FaMYB11 , FabHLH3 and FaTTG1 are the respective functional homologues of AtTT2 , AtTT8 and AtTTG1 , providing new tools for modifying PA content and strawberry fruit quality.