Comparative Analysis of the Triplicate Proathocyanidin Regulators in Lotus japonicus

Proanthocyanidins (PAs), which are flavonoid compounds widely distributed in the plant kingdom, protect against environmental stress. The accumulation of PAs is regulated by a ternary transcriptional complex comprising the R2R3-MYB transcription factor, a basic helix-loop-helix (bHLH) transcription...

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Published in:Plant and cell physiology 2010-06, Vol.51 (6), p.912-922
Main Authors: Yoshida, Kazuko, Kume, Nao, Nakaya, Yumi, Yamagami, Ayumi, Nakano, Takeshi, Sakuta, Masaaki
Format: Article
Language:English
Subjects:
Amino Acid Sequence
Amino Acid Substitution
Arabidopsis - metabolism
Gene duplication
Gene Expression Regulation, Plant
Loteae - genetics
Loteae - metabolism
Lotus japonicus
Molecular Sequence Data
Multigene Family
Mutagenesis, Site-Directed
Mutation
MYB
Plant Proteins - genetics
Plant Proteins - metabolism
Plants, Genetically Modified - genetics
Plants, Genetically Modified - metabolism
Proanthocyanidin
Proanthocyanidins - biosynthesis
RNA, Plant - genetics
Transcription factor
Transcription Factors - genetics
Transcription Factors - metabolism
Transcriptional Activation
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Summary:Proanthocyanidins (PAs), which are flavonoid compounds widely distributed in the plant kingdom, protect against environmental stress. The accumulation of PAs is regulated by a ternary transcriptional complex comprising the R2R3-MYB transcription factor, a basic helix-loop-helix (bHLH) transcription factor and a WD40 repeat (WDR) protein. Recently, multigene families of the R2R3-MYB-type PA regulators from Lotus japonicus, LjTT2a, b and c, were isolated and characterized. Although their roles as transcription factors that up-regulate PA biosynthetic genes have been elucidated, the significance of their redundancies and functions in planta is unknown. In this study, we characterized LjTT2a, b and c to elucidate their functions in planta and determine differences in transcriptional activation properties. Transgenic studies demonstrated that LjTT2a could induce ectopic PA accumulation in Arabidopsis. Further analysis of the LjTT2 multigene family using a transient expression system revealed differences in transcriptional activities in cooperation with WDR and bHLH proteins isolated from L. japonicus. In-depth characterization of chimeric constructs of three LjTT2s, as well as site-directed mutagenesis in R2-MYB domains, identified the amino acid residues that affect the level of transcriptional activation of LjTT2.
ISSN:0032-0781
1471-9053
DOI:10.1093/pcp/pcq067