Present address: Laboratoire de Morphogenèse des Ligneux, UMR A-462 SAGAH Université d’Angers-INRA-INH, UFR Sciences, 2 Boulevard Lavoisier, 49045 Angers Cedex 01, France.
MYBL2 is a new regulator of flavonoid biosynthesis in Arabidopsis thaliana
Article first published online: 4 JUN 2008
© 2008 The Authors. Journal compilation © 2008 Blackwell Publishing Ltd
The Plant Journal
Volume 55, Issue 6, pages 940–953, September 2008
How to Cite
Dubos, C., Le Gourrierec, J., Baudry, A., Huep, G., Lanet, E., Debeaujon, I., Routaboul, J.-M., Alboresi, A., Weisshaar, B. and Lepiniec, L. (2008), MYBL2 is a new regulator of flavonoid biosynthesis in Arabidopsis thaliana. The Plant Journal, 55: 940–953. doi: 10.1111/j.1365-313X.2008.03564.x
- Issue published online: 4 SEP 2008
- Article first published online: 4 JUN 2008
- Received 8 February 2008; revised 23 April 2008; accepted 7 May 2008; published online 11 July 2008.
In Arabidopsis thaliana, several MYB and basic helix-loop-helix (BHLH) proteins form ternary complexes with TTG1 (WD-Repeats) and regulate the transcription of genes involved in anthocyanin and proanthocyanidin (PA) biosynthesis. Similar MYB-BHLH-WDR (MBW) complexes control epidermal patterning and cell fates. A family of small MYB proteins (R3-MYB) has been shown to play an important role in the regulation of epidermal cell fates, acting as inhibitors of the MBW complexes. However, so far none of these small MYB proteins have been demonstrated to regulate flavonoid biosynthesis. The genetic and molecular analyses presented here demonstrated that Arabidopsis MYBL2, which encodes a R3-MYB-related protein, is involved in the regulation of flavonoid biosynthesis. The loss of MYBL2 activity in the seedlings of two independent T-DNA insertion mutants led to a dramatic increase in the accumulation of anthocyanin. In addition, overexpression of MYBL2 in seeds inhibited the biosynthesis of PAs. These changes in flavonoid content correlate well with the increased level of mRNA of several structural and regulatory anthocyanin biosynthesis genes. Interestingly, transient expression analyses in A. thaliana cells suggested that MYBL2 interacts with MBW complexes in planta and directly modulates the expression of flavonoid target genes. These results are fully consistent with the molecular interaction of MYBL2 with BHLH proteins observed in yeast. Finally, MYBL2 expression studies, including its inhibition by light-induced stress, allowed us to hypothesise a physiological role for MYBL2. Taken together, these results bring new insights into the transcriptional regulation of flavonoid biosynthesis and provide new clues and tools for further investigation of its developmental and environmental regulation.