Abstract
BackgroundBecause flavonoids and trichomes play crucial roles in plant defence, their formation requires fine transcriptional control by multiple transcription factor families. However, little is known regarding the mechanism of the R2R3-MYB transcription factors that regulate both flavonoid metabolism and trichome development.ResultsHere, we identified a unique SG4-like-MYB TF from Tartary buckwheat, FtMYB8, which harbours the C2 repression motif and an additional TLLLFR repression motif. The expression profiles of FtMYB8 combined with the transcriptional activity of PFtMYB8 promoter showed that FtMYB8 mRNA mainly accumulated in roots during the true leaf stage and flowering stage and in bud trichomes and flowers, and the expression of this gene was markedly induced by MeJA, ABA and UV-B treatments but repressed by dark treatment. Overexpression of FtMYB8 in Arabidopsis reduces the accumulation of anthocyanin/proanthocyanidin by specifically inhibiting TT12 expression, which may depend on the interaction between FtMYB8 and TT8. Interestingly, this interaction may also negatively regulate the marginal trichome initiation in Arabidopsis leaves.ConclusionsTaken together, our results suggest that FtMYB8 may fine-tune the accumulation of anthocyanin/proanthocyanidin in the roots and flowers of Tartary buckwheat by balancing the inductive effects of transcriptional activators, and probably regulate trichome distribution in the buds of Tartary buckwheat.
Highlights
Because flavonoids and trichomes play crucial roles in plant defence, their formation requires fine transcriptional control by multiple transcription factor families
Our results indicate that FtMYB8, the first unique R2R3-MYB Transcription factors (TFs) gene identified to date, inhibits both anthocyanin/PA accumulation and marginal trichome initiation at specific developmental stages and in response to hormone signals and environmental factors
Expression analysis and validation of Sub-group 4 (SG4)-like-MYBs Based on the genomic database [24] and our transcriptomic database, SG4-like-MYBs were identified in Tartary buckwheat
Summary
Because flavonoids and trichomes play crucial roles in plant defence, their formation requires fine transcriptional control by multiple transcription factor families. Little is known regarding the mechanism of the R2R3-MYB transcription factors that regulate both flavonoid metabolism and trichome development. The transcription of enzyme-encoding genes in the flavonoid pathway is regulated by multiple TFs, which mainly include WD40s, bHLHs and MYBs [2]. Among these TFs, The R2R3-MYB TF sub-family, which is deemed the largest sub-family of MYB TFs in Arabidopsis thaliana, has been classified into 23 sub-groups [3]. Among the R2R3-MYB TFs identified far in Arabidopsis, only members of SG4, including AtMYB32, AtMYB7, AtMYB4 and AtMYB3, function as separate transcription repressors in the phenylpropanoid pathway [3,4,5,6].
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