Regulation anthocyanin accumulation

R2R3 MYB and HLH transcription factors acting in concert (Table 3.1). More recently, proteins containing conserved WD40 repeats have been implicated in the regulation of flavonoid biosynthesis as well. Thus, it is by variations of the combination of MYB/HLH/WD factors that anthocyanin accumulation is controlled (Table 3.1). 

The dwarf mutants of Arabidopsis show, when grown in the dark, many of the characteristics of light-grown plants, including cotyledon expansion, primary leaf initiation, anthocyanin accumulation, and depression of light-regulated gene expression. Involvement of BR in de-etiolation has been discussed.816... 

Faragher JD (1983) Temperature regulation of anthocyanin accumulation in apple skin. J Exp Bot 34 1291-1298... 

Cell line selection is one of the traditional and effective approaches to enhancing metabolite accumulation, and biochemical studies provide the fundamental information for the intentional regulation of secondary metabolism in plant cells. In a carrot suspension culture regulated by 2,4-dichlorophenoxyace-tic acid, Ozeki et al. [7] found that there was a correlation between anthocyanin synthesis and morphological differentiation for somatic embryogenesis they also demonstrated the induction and repression of phenylalanine ammonia lyase (PAL) and chalcone synthase correlated with formation of the respective mRNAs. Two biosynthetic enzymes, i. e., PAL and 3-hydroxymethylglutaryl-CoA reductase, were also related with shikonin formation in Lithospermum erythro-rhizon cultures [8]. 

As we begin to unravel the molecular mechanisms of the regulation of anthocyanin biosynthesis, we must remember that evolution and selection had significant opportunities to explore new ways to color plants, flowers, and seeds. Model plant systems such as maize, petunia, and Arabidopsis will continue to provide the framework to understand how pigment accumulation is controlled. However, it is important to investigate how nature has exploited variations in these central prototypes to provide the amazing diversity found today in the type and distribution of anthocyanin pigments. 

Interestingly, the levels of all the extractable flavonoids in the leaves of B. napus plants are decreased in a dose-dependent manner in response to UVA exposure. Additionally, the accumulation of the extractable flavonoids was examined by a shift from the photosynthetically active radiation (PAR) + UVA to PAR + UVB to assess whether the preexposure of the UVA affects the UVB-induced flavonoid accumulation. The UVA preexposures inhibited the UVB-induced accumulation of some flavonoids. This down regulation was particularly evident for quercetin-3-O-sophoroside and quercetin-3-O-sophoroside-7-O-glucoside of two anthocyanins. This is very interesting because the induction of quercetin by UVB is correlated with the UVB tolerance in some plant species. The photobiological nature of these UVA-mediated effects on flavonoid accumulation might suggest complex interactions between the UVA and UVB responses [66]. 

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