title: Comparative analysis of the triplicate proathocyanidin regulators in Lotus japonicus.
abstract: 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.
authors.affiliation: Department of Biological Sciences, Ochanomizu University, Tokyo, 112-8610 Japan.
authors.forename: Kazuko
authors.initials: K
authors.lastname: Yoshida
authors.forename: Nao
authors.initials: N
authors.lastname: Kume
authors.forename: Yumi
authors.initials: Y
authors.lastname: Nakaya
authors.forename: Ayumi
authors.initials: A
authors.lastname: Yamagami
authors.forename: Takeshi
authors.initials: T
authors.lastname: Nakano
authors.forename: Masaaki
authors.initials: M
authors.lastname: Sakuta
mesh_terms: D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D017360:Arabidopsis / Q000378:metabolism; D018506:Gene Expression Regulation, Plant; D000070116:Lotus / Q000235:genetics* / Q000378:metabolism; D008969:Molecular Sequence Data; D005810:Multigene Family; D016297:Mutagenesis, Site-Directed; D009154:Mutation; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism*; D030821:Plants, Genetically Modified / Q000235:genetics / Q000378:metabolism; D044945:Proanthocyanidins / Q000096:biosynthesis*; D018749:RNA, Plant / Q000235:genetics; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*; D015533:Transcriptional Activation
chemical_list: D010940:Plant Proteins; D044945:Proanthocyanidins; D018749:RNA, Plant; D014157:Transcription Factors