Members of an R2R3‐MYB transcription factor family in Petunia are developmentally and environmentally regulated to control complex floral and vegetative pigmentation patterning

Abstract

SUMMARYWe present an investigation of anthocyanin regulation over the entire petunia plant, determining the mechanisms governing complex floral pigmentation patterning and environmentally induced vegetative anthocyanin synthesis. DEEP PURPLE (DPL) and PURPLE HAZE (PHZ) encode members of the R2R3-MYB transcription factor family that regulate anthocyanin synthesis in petunia, and control anthocyanin production in vegetative tissues and contribute to floral pigmentation. In addition to these two MYB factors, the basic helix-loop-helix (bHLH) factor ANTHOCYANIN1 (AN1) and WD-repeat protein AN11, are also essential for vegetative pigmentation. The induction of anthocyanins in vegetative tissues by high light was tightly correlated to the induction of transcripts for PHZ and AN1. Interestingly, transcripts for PhMYB27, a putative R2R3-MYB active repressor, were highly expressed during non-inductive shade conditions and repressed during high light. The competitive inhibitor PhMYBx (R3-MYB) was expressed under high light, which may provide feedback repression. In floral tissues DPL regulates vein-associated anthocyanin pigmentation in the flower tube, while PHZ determines light-induced anthocyanin accumulation on exposed petal surfaces (bud-blush). A model is presented suggesting how complex floral and vegetative pigmentation patterns are derived in petunia in terms of MYB, bHLH and WDR co-regulators.

The MYB182 Protein Down-Regulates Proanthocyanidin and Anthocyanin Biosynthesis in Poplar by Repressing Both Structural and Regulatory Flavonoid Genes

“…This is consistent with the idea that MYB182 could have a negative effect on PA accumulation. Such negative correlations in developmental expression have been observed with AtMYBL2, PhMYB27, and VvMYBC2-L1 repressors (Dubos et al, 2008;Albert et al, 2011;Huang et al, 2014). We next used reverse transcription-quantitative PCR (RT-qPCR) to confirm that MYB182 expression is up-regulated in MYB134-overexpressing poplars, as this is how it was first identified (Supplemental Fig.…”

Competition between anthocyanin and flavonol biosynthesis produces spatial pattern variation of floral pigments between Mimulus species

“…Studies in snapdragon (Antirrhinum majus) and petunia (Petunia hybrida) have revealed a conserved mechanism for the formation of vein-associated anthocyanin pigmentation pattern in petal epidermis. Pigments are only produced in the overlapping expression domains of the R2R3-MYB and bHLH coregulators of anthocyanin biosynthetic genes; the bHLH expression is confined to the petal epidermis and the R2R3-MYB expression is specific to cells above the vascular bundles (8,12,13). However, the molecular basis of variation in this color pattern among natural species is less clear, although in the case of Antirrhinum, the R2R3-MYB, Venosa, was implicated as the causal gene, explaining much of the natural variation (8,12).…”

Transcriptional regulators of flavonoid biosynthesis and their application to flower color modification in Japanese gentians

“…Similarly, jasmonate ZIMdomain (JAZ) protein interacts with the PAP1-TT8/GL3-TTG1 complex and represses anthocyanin accumulation (Qi et al 2011). PhMYBx (R3-MYB) is also proposed to act as an inhibitor of anthocyanin biosynthesis in vegetative tissues of petunia (Albert et al 2014;Albert et al 2011). We have also isolated two single-repeat R3MYB transcription factors, GtMYB1R1 and GtMYB1R9, from a gentian petal cDNA library.…”

“…A few novel R2R3MYB genes have recently been characterized in petunia: DEEP PURPLE (DPL) regulating vein-associated anthocyanin pigmentation in flower tubes and PURPLE HAZE (PHZ) determining light-induced anthocyanin accumulation on exposed petal surfaces (bud-blush) (Albert et al 2011). In Asiatic hybrid lilies, LhMYB6 and LhMYB12 together with LhbHLH2 regulate anthocyanin pigmentation in specific organs (Yamagishi et al 2010).…”