Journal Article

Comparative Analysis of the Triplicate Proathocyanidin Regulators in <i>Lotus japonicus</i>

Kazuko Yoshida, Nao Kume, Yumi Nakaya, Ayumi Yamagami, Takeshi Nakano and Masaaki Sakuta

in Plant and Cell Physiology

Published on behalf of Japanese Society of Plant Physiologists

Volume 51, issue 6, pages 912-922
Published in print June 2010 | ISSN: 0032-0781
Published online May 2010 | e-ISSN: 1471-9053 | DOI: http://dx.doi.org/10.1093/pcp/pcq067
Comparative Analysis of the Triplicate Proathocyanidin Regulators in Lotus japonicus

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  • Biochemistry
  • Molecular and Cell Biology
  • Plant Sciences and Forestry

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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.

Keywords: Gene duplication; Lotus japonicus; MYB; Proanthocyanidin; Transcription factor

Journal Article.  5745 words.  Illustrated.

Subjects: Biochemistry ; Molecular and Cell Biology ; Plant Sciences and Forestry

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