A bHLH transcription factor, DvIVS, is involved in regulation of anthocyanin synthesis in dahlia (Dahlia variabilis)

Abstract

Dahlias (Dahlia variabilis) exhibit a wide range of flower colours because of accumulation of anthocyanin and other flavonoids in their ray florets. Two lateral mutants were used that spontaneously occurred in ‘Michael J’ (MJW) which has yellow ray florets with orange variegation. MJOr, a bud mutant producing completely orange ray florets, accumulates anthocyanins, flavones, and butein, and MJY, another mutant producing completely yellow ray florets, accumulates flavones and butein. Reverse transcription–PCR analysis showed that expression of chalcone synthase 1 (DvCHS1), flavanone 3-hydroxylase (DvF3H), dihydroflavonol 4-reductase (DvDFR), anthocyanidin synthase (DvANS), and DvIVS encoding a basic helix–loop–helix transcription factor were suppressed, whereas that of chalcone isomerase (DvCHI) and DvCHS2, another CHS with 69% nucleotide identity with DvCHS1, was not suppressed in the yellow ray florets of MJY. A 5.4 kb CACTA superfamily transposable element, transposable element of Dahlia variabilis 1 (Tdv1), was found in the fourth intron of the DvIVS gene of MJW and MJY, and footprints of Tdv1 were detected in the variegated flowers of MJW. It is shown that only one type of DvIVS gene was expressed in MJOr, whereas these plants are likely to have three types of the DvIVS gene. On the basis of these results, the mechanism regulating the formation of orange and yellow ray florets in dahlia is discussed.

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.…”

“…These factors form a complex that binds to the anthocyanin structural gene promoter to control its transcription (Grotewold et al, 2000;Gonzalez et al, 2008;Schaart et al, 2013). In many plants, the mutation of anthocyanin-related genes usually causes color variation, such as in Vitis vinifera (Kobayashi et al, 2004), Dahlia (Ohno et al, 2011), and Tulipa fosteriana (Toda et al, 2002;Yuan et al, 2014). Uncovering anthocyanin-related genes using a traditional method for plants without a reference genome is time consuming.…”

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

“…While this feature is present in both petunia and Arabidopsis (Baudry et al, 2006;Xu et al, 2013), this does not seem to be necessary in Arabidopsis for pigmentation to occur, as GL3/EGL3 (bHLH1) can act redundantly with TT8 (bHLH2) for anthocyanin synthesis (Zhang et al, 2003). By contrast, petunia (Spelt et al, 2000, Albert et al, 2011, Ipomoea sp (Park et al, 2004), pea (Pisum sativa; Hellens et al, 2010), and Dahlia variabilis (Ohno et al, 2011) bHLH2 mutants result in a complete or severe loss of anthocyanin pigmentation, despite the continued expression of bHLH1 having been shown in the case of petunia, Ipomoea, and Dahlia. Thus, it appears that the requirement of bHLH2 activity for anthocyanin synthesis, and the hierarchical regulation between bHLH components, varies throughout the Eudicots and likely reflects functional specialization of the bHLH factor roles between genera.…”

Simultaneous post-transcriptional gene silencing of two different chalcone synthase genes resulting in pure white flowers in the octoploid dahlia

“…All these CHS genes have conserved CHS active site residues (Ferrer et al 1999;Ma et al 2009) and the characteristic intron insertion site conserved in polyketide synthase (Zheng et al 2001). In addition to this, 12 sequences of DvCHS1 mRNA and 2 sequences of DvCHS2 mRNA are expressed in petals of a bicolor cultivar 'Michael J' (Ohno et al 2011). In the seed coats of yellow soybean (Glycine max), which has nine CHS, all CHS are simultaneously silenced by post-transcriptional gene silencing (PTGS) (Kurauchi et al 2009;Tuteja et al 2009).…”