|Chiu, Li-Wei -|
Submitted to: Planta
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: May 29, 2012
Publication Date: May 29, 2012
Citation: Chiu, L., Li, L. 2012. Characterization of the regulatory network of BoMYB2 in controlling anthocyanin biosynthesis in purple cauliflower. Planta. 236:1153-1164. Interpretive Summary: Foods enriched in anthocyanins have been implicated to offer protection against a number of chronic diseases. A fully understanding of regulation of anthocyanin biosynthesis is important to develop anthocyanin-rich foods to meet the increasing demand for health-promoting components in our diet. Despite our significant progress, the regulatory control of anthocyanins remains to be fully understood. BoMYB2 controls high levels of anthocyanin accumulation in purple cauliflower mutant. In this study, we investigated the interaction between BoMYBs and other cauliflower WBM network proteins and examined the interplay of BoMYB2 with bHLH transcription factors in planta. We found that MYB transcription factors regulate the bHLH gene expression, which may represent a critical feature in the control of specific accumulation of anthocyanins. The bHLH transcription factors of TT8, EGL3, and GL3 were all involved in the BoMYB2 mediated anthocyanin accumulation. Our findings provide additional information for the complicated regulatory network of anthocyanin biosynthesis and the transcriptional regulation of transcription factors in vegetable crops.
Technical Abstract: Purple cauliflower (Brassica oleracea L. var. botrytis) Graffiti represents a unique mutant in conferring ectopic anthocyanin biosynthesis, which is caused by the tissue specific activation of BoMYB2, an ortholog of Arabidopsis PAP2 or MYB113. To gain a better understanding of the regulatory network of anthocyanin biosynthesis, we investigated the interaction among cauliflower MYB-bHLH-WD40 (MBW) network proteins and examined the interplay of BoMYB2 with various bHLH transcription factors in planta. Yeast two-hybrid studies revealed that cauliflower BoMYBs along with the other regulators formed the MBW complexes and BobHLH1 acted as a bridge between BoMYB and BoWD40-1 proteins. Different BoMYBs exhibited different binding activity to BobHLH1. Examination of the BoMYB2 transgenic lines in Arabidopsis bHLH mutant backgrounds demonstrated that TT8, EGL3, and GL3 were all involved in the BoMYB2 mediated anthocyanin biosynthesis. Expression of BoMYB2 in Arabidopsis caused up-regulation of AtTT8 and AtEGL3 as well as a subset of anthocyanin structural genes encoding flavonoid 3’hydroxylase, dihydroflavonol 4-reductase, and leucoanthocyanidin dioxygenase. Taken together, our results show that MYB transcription factors regulated the bHLH gene expression, which may represent a critical feature in the control of anthocyanin biosynthesis. BoMYB2 together with various BobHLHs specifically regulated the late anthocyanin biosynthetic pathway genes for anthocyanin biosynthesis. Our findings provide additional information for the complicated regulatory network of anthocyanin biosynthesis and the transcriptional regulation of transcription factors in vegetable crops.