TCP3 interacts with R2R3‐MYB proteins, promotes flavonoid biosynthesis and negatively regulates the auxin response in Arabidopsis thaliana. (12th November 2013)

• Record Type: Journal Article
• Authors: Li, Shutian; Zachgo, Sabine
• Is Part Of: Plant journal. Volume 76:Number 6(2013:Dec.)
• Page Start: 901
• Page End: 913
• Publication Date: 2013-11-12
• Subjects: Plant molecular biology -- Periodicals; Plant cells and tissues -- Periodicals; Botany -- Periodicals; 580
• DOI: 10.1111/tpj.12348
• Languages: English
• ISSNs: 0960-7412

Abstract

<abstract abstract-type="main" id="tpj12348-abs-0001"> <title>Summary</title> <p>TCP proteins belong to the plant‐specific bHLH transcription factor family, and function as key regulators of diverse developmental processes. Functional redundancy amongst family members and post‐transcriptional down‐regulation by <italic>miRJAW</italic> of several <italic>TCP</italic> genes complicate their functional characterization. Here, we explore the role of <italic>TCP3</italic> by analyzing transgenic plants expressing <italic>miRJAW</italic>‐resistant <italic>mTCP3</italic> and dominant‐negative <italic>TCP3SRDX</italic>. Seedlings and seeds of <italic>mTCP3</italic> plants were found to hyper‐accumulate flavonols, anthocyanins and proanthocyanidins, whereas levels of proanthocyanidins were slightly reduced in <italic>TCP3SRDX</italic> plants. R2R3‐MYB proteins control not only early flavonoid biosynthetic steps but also activate late flavonoid biosynthetic genes by forming ternary R2R3‐MYB/bHLH/WD40 (MBW) complexes. TCP3 interacted in yeast with R2R3‐MYB proteins, which was further confirmed <italic>in planta</italic> using BiFC experiments. Yeast three‐hybrid assays revealed that TCP3 significantly strengthened the transcriptional activation capacity of R2R3‐MYBs bound by the bHLH protein TT8. Transcriptome analysis of <italic>mTCP3</italic> and <italic>TCP3SRDX</italic> plants supported a role for <italic>TCP3</italic> in enhancing flavonoid biosynthesis. Moreover, several auxin‐related developmental abnormalities were observed in <italic>mTCP3</italic> plants. Transcriptome data coupled with studies of an auxin response reporter and auxin efflux carriers showed that <italic>TCP3</italic> negatively modulates the auxin response, probably by compromising auxin transport capacity. Genetic experiments revealed that the chalcone synthase mutant <italic>tt4‐11</italic> lacking flavonoid biosynthesis abrogated the auxin‐related defects caused by <italic>mTCP3</italic>. Together, these data suggest that TCP3 interactions with R2R3‐MYBs lead to enhanced flavonoid production, which further negatively modulates the auxin response.</p> </abstract>