Genetic regulation and photocontrol of anthocyanin accumulation in maize seedlings.

Abstract

The flavonoid pathway leading to anthocyanin biosynthesis in maize is controlled by multiple regulatory genes and induced by various developmental and environmental factors. We have investigated the effect of the regulatory loci R, B, and f / on anthocyanin accumulation and on the expression of four genes ( C2, A l , 621, and 822) in the biosynthetic pathway during an inductive light treatment. The results show that light-mediated anthocyanin biosynthesis is regulated solely by R; the contributions of B and f / are negligible in young seedlings. lnduction of the A1 and Bz2 genes by high fluence-rate white light requires the expression of a dominant R allele, whereas accumulation of C2 and Bzl mRNA occurs with either a dominant or recessive allele at R. A1 and 822 mRNA accumulate only in response to high fluence-rate white light, but Bzl is fully expressed in dim red light. Some C2 mRNA is induced by dim red light, but accumulation is far greater in high fluence-rate white light. Furthe'more, expression from both dominant and recessive alleles of the regulatory gene R is enhanced by high fluence-rate white light. Seedlings with a recessive allele at R produce functional chalcone synthase protein (the C2 gene product) but accumulate no anthocyanins, suggesting that, in contrast to the R-mediated coordinate regulation of C2 and Bzl observed in the aleurone, C2 expression in seedlings is independent of R and appears to be regulated by a different light-sensitive pathway.

Ultraviolet-B-Responsive Anthocyanin Production in a Rice Cultivar Is Associated with a Specific Phase of Phenylalanine Ammonia Lyase Biosynthesis

“…'me product of the IP locus was found to be a transcripticm activator protein of the helix-loop-helix class that interacts with the regulatory elements of a number of structural genes of the pathway. Most importantly, the R locus was found to be largely responsible for the photoinduction of anthocyanin synthesis in seedlings (Taylor and Briggs, 1990). It is reasonable to suggest, therefore, that the UV-B-induced anthocyanin synthesis in rice may be mediated by the UV-B-dependent expression of a regulatory gene analogous to the R locus of maize.…”

A Proteolytic Regulator Controlling Chalcone Synthase Stability and Flavonoid Biosynthesis in Arabidopsis

“…In Arabidopsis and many other species, anthocyanin production is a feature of light-grown plants for their photomorphogenesis, and in the dark-grown plants, the synthesis does not occur (Taylor and Briggs, 1990;Kubasek et al, 1992). The involvement of KFB CHS in regulating light-induced flavonoid synthesis is perceived from its substantial alteration in gene expression during the early period of the switch of Arabidopsis seedlings from dark to light or from light to dark (Figure 6).…”

Flavonoid Biosynthesis in Bilberry (Vaccinium Myrtillus L.)

“…Transcriptional control of the structural genes of the flavonoid biosynthetic pathway has been most intensively studied in relation to the biosynthesis of anthocyanins. Groundbreaking research concerning the expression of the structural and regulatory genes of the flavonoid pathway has been done with maize (Zea mays) (Goff et al 1990, Taylor et al 1990, Tonelli et al 1991, arabidopsis (Arabidopsis thaliana) (Shirley et al 1992) and with ornamental plants like snapdragon (Antirrhinum majus) (Martin et al1991), petunia (van der Krol et al 1988 and gerbera . Naturally occurring flavonoid mutants and variants, or genetically transformed mutant plants have been important tools in several investigations clarifying the functions of the flavonoid pathway genes (Shirley et al 1995, Tanaka et al 1998.…”