The Purple Cauliflower Arises from Activation of a MYB Transcription Factor

Abstract

Anthocyanins are responsible for the color of many flowers, fruits, and vegetables. An interesting and unique Purple (Pr) gene mutation in cauliflower (Brassica oleracea var botrytis) confers an abnormal pattern of anthocyanin accumulation, giving the striking mutant phenotype of intense purple color in curds and a few other tissues. To unravel the nature of the Pr mutation in cauliflower, we isolated the Pr gene via a combination of candidate gene analysis and fine mapping. Pr encoded a R2R3 MYB transcription factor that exhibited tissue-specific expression, consistent with an abnormal anthocyanin accumulation pattern in the mutant. Transgenic Arabidopsis (Arabidopsis thaliana) and cauliflower plants expressing the Pr-D allele recapitulated the mutant phenotype, confirming the isolation of the Pr gene. Up-regulation of Pr specifically activated a basic helix-loop-helix transcription factor and a subset of anthocyanin structural genes encoding flavonoid 3’-hydroxylase, dihydroflavonol 4-reductase, and leucoanthocyanidin dioxygenase to confer ectopic accumulation of pigments in the purple cauliflower. Our results indicate that the genetic variation including a Harbinger DNA transposon insertion in the upstream regulatory region of the Pr-D allele is responsible for the up-regulation of the Pr gene in inducing phenotypic change in the plant. The successful isolation of Pr provides important information on the regulatory control of anthocyanin biosynthesis in Brassica vegetables, and offers a genetic resource for development of new varieties with enhanced health-promoting properties and visual appeal.

Transcriptome analysis and anthocyanin-related genes in red leaf lettuce

“…In plants, the MYB-bHLH-WD40 complex is critical for activating the anthocyanin biosynthesis pathway. The mutation of these regulated genes usually causes color variation in apple (Espley et al, 2007), purple cauliflower (Chiu et al, 2010), Dahlia (Ohno et al, 2011), and blood oranges (Butelli et al, 2012). Anthocyaninregulated genes were found to be useful for increasing food quality.…”

A Conserved Network of Transcriptional Activators and Repressors Regulates Anthocyanin Pigmentation in Eudicots

“…Notably, however, CPC variants lacking the motif were capable of intercellular movement in roots, suggesting passive diffusion as a secondary transport mechanism (Rim et al, 2011). An alternative interpretation of the biolistic data is that MYBx prevented AN11 from moving; however, this is unlikely given that the MYBs are not effective binders of WDR proteins (Figure 1; Payne et al, 2000;Baudry et al, 2004Baudry et al, , 2006Chiu et al, 2010;An et al, 2012).…”

The Methylation of the PcMYB10 Promoter Is Associated with Green-Skinned Sport in Max Red Bartlett Pear

“…For example, mutations in the structural genes CHS (for chalcone synthase), DFR (for dihydroflavonol 4-reductase), and ANS (for anthocyanidin synthase) involved in anthocyanin biosynthesis cause flower color changes (Stracke et al, 2009;Tanaka et al, 2009;Vanholme et al, 2010). Genetic mutations causing color changes of plant organs also occur in genes regulating anthocyanin biosynthesis, such as transcription factors (Boss et al, 1996;Morita et al, 2006;Park et al, 2007;Allan et al, 2008;Chiu et al, 2010). The transcription factors involved in anthocyanin biosynthesis include R2R3-MYB, bHLH (for basic helix-loop-helix), and WDR (for WD-repeat protein), which regulate the downstream structural genes by forming the MYBbHLH-WD40 complex, which is involved in the anthocyanin biosynthesis pathway (Holton and Cornish, 1995;Winkel-Shirley, 2001;Schwinn et al, 2006;Gonzalez et al, 2008).…”

“…Mutations including nucleotide substitutions, deletions, and insertions in the MYB gene result in color changes in plant organs (Boss et al, 1996;Morita et al, 2006). Transposon insertions in the bHLH gene cause white flowers in common morning glory (Ipomoea purpurea; Park et al, 2007), whereas simultaneous mutations of a nucleotide deletion in MYB and a nucleotide insertion in WDR change morning glory flower color from blue to white (Chiu et al, 2010).…”