Transcriptional regulation of flavonoid biosynthesis in nectarine (Prunus persica) by a set of R2R3 MYB transcription factors

Abstract

BackgroundFlavonoids such as anthocyanins, flavonols and proanthocyanidins, play a central role in fruit colour, flavour and health attributes. In peach and nectarine (Prunus persica) these compounds vary during fruit growth and ripening. Flavonoids are produced by a well studied pathway which is transcriptionally regulated by members of the MYB and bHLH transcription factor families. We have isolated nectarine flavonoid regulating genes and examined their expression patterns, which suggests a critical role in the regulation of flavonoid biosynthesis.ResultsIn nectarine, expression of the genes encoding enzymes of the flavonoid pathway correlated with the concentration of proanthocyanidins, which strongly increases at mid-development. In contrast, the only gene which showed a similar pattern to anthocyanin concentration was UDP-glucose-flavonoid-3-O-glucosyltransferase (UFGT), which was high at the beginning and end of fruit growth, remaining low during the other developmental stages. Expression of flavonol synthase (FLS1) correlated with flavonol levels, both temporally and in a tissue specific manner. The pattern of UFGT gene expression may be explained by the involvement of different transcription factors, which up-regulate flavonoid biosynthesis (MYB10, MYB123, and bHLH3), or repress (MYB111 and MYB16) the transcription of the biosynthetic genes. The expression of a potential proanthocyanidin-regulating transcription factor, MYBPA1, corresponded with proanthocyanidin levels. Functional assays of these transcription factors were used to test the specificity for flavonoid regulation.ConclusionsMYB10 positively regulates the promoters of UFGT and dihydroflavonol 4-reductase (DFR) but not leucoanthocyanidin reductase (LAR). In contrast, MYBPA1 trans-activates the promoters of DFR and LAR, but not UFGT. This suggests exclusive roles of anthocyanin regulation by MYB10 and proanthocyanidin regulation by MYBPA1. Further, these transcription factors appeared to be responsive to both developmental and environmental stimuli.

Gene regulation of anthocyanin biosynthesis in two blood-flesh peach (Prunus persica (L.) Batsch) cultivars during fruit development

“…Anthocyanin accumulation was found to be initiated early, at about 50 d after full bloom (DAFB) (Shen et al, 2013). A similar profile for anthocyanin accumulation was observed in the skin and flesh of 'Stark Red Gold' nectarines (Ravaglia et al, 2013). Taken together, these cultivars provide interesting models for dissecting the mechanisms involved in anthocyanin accumulation.…”

“…These findings suggest that PpUFGT is likely more highly regulated than the other flavonoid genes. Furthermore, Ravaglia et al (2013) reported that PpMYB10 positively regulates the promoters of PpUFGT and PpDFR. Our qPCR results show that the expression pattern of the PpMYB10 gene is highly correlated with PpUFGT and PpDFR in 'Heiyoutao', but not in 'Beijingyixianhong'.…”

“…For instance, the TFs of anthocyanin biosynthesis in Arabidopsis were found to contain an R2R3-MYB domain, a basic helix-loop-helix (bHLH) domain, and WD40 repeats (WDRs) (Morita et al, 2006) that work together to control the expression of the gene involved in the catalysis of the biosynthesis of anthocyanin (Baudry et al, 2004;Lepiniec et al, 2006). Similarly, the induction of anthocyanin biosynthesis in transient assays using MYB10 is dependent on the co-expression of the bHLH3 domain in peach (Ravaglia et al, 2013) and apple (Espley et al, 2007).…”

Poplar MYB115 and MYB134 Transcription Factors Regulate Proanthocyanidin Synthesis and Structure

“…Although MYB115 orthologs have been studied in fruit of grapevine, persimmon, nectarine, and cocoa (Theobroma cacao; Terrier et al, 2009;Akagi et al, 2010;Ravaglia et al, 2013;Liu et al, 2015), our study focuses on a member of this group that is active in leaves. Our data showed that MYB115 transcripts were induced by wounding, and gene expression profiling confirmed that MYB115 is highly expressed in developing leaves where the PA pathway is most active.…”

“…Black arrows indicate the major metabolic routes to PAs in poplar leaves. Akagi et al, 2009;Ravaglia et al, 2013). VvMYBPA1 enhances PA accumulation when overexpressed in transgenic grapevine hairy root cultures, but also acts in conjunction with the TT2-like VvMYBPA2 (Terrier et al, 2009).…”