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 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.
Yoshida
Kazuko
K
Department of Biological Sciences, Ochanomizu University, Tokyo, 112-8610 Japan.
Kume
Nao
N
Nakaya
Yumi
Y
Yamagami
Ayumi
A
Nakano
Takeshi
T
Sakuta
Masaaki
M
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
D010940:Plant Proteins; D044945:Proanthocyanidins; D018749:RNA, Plant; D014157:Transcription Factors