Submitted to: BARC Poster Day
Publication Type: Other
Publication Acceptance Date: April 6, 2006
Publication Date: April 26, 2006
Citation: Lightbourn, G., Winkel, B., Griesbach, R., Stommel, J.R. 2006. Capsicum annuum: A model for elucidating gene regulation in the anthocyanin biosynthetic pathway [abstract]. Seventeenth Annual BARC Poster Day. Abstract #22, p. 31.
Horticultural crops have been selected and bred for a number of characters that enhance their visual appeal, nutritive value, and suitability for various market applications. Color pigments are usually associated with flowers and fruits and in some cases, modified leaves associated with flowers. Color is attributed to several pigments, including the chlorophylls, carotenoids, flavonoids and betalains. Flavonoids can be further divided into copigments (colorless) and anthocyanins (colored). In pepper (Capsicum annuum), anthocyanins impart violet to black pigmentation and may accumulate in fruits, foliage, stems, and flower parts. Utilizing genetic stocks developed for their varied pigmentation across these various tissue types and differential pigment accumulation in response to environmental stress, we are characterizing the tissue-specific gene expression which accounts for the observed phenotypes. Biochemical analysis revealed that violet pigmentation in pepper fruit was attributed to the anthocyanin delphinidin, whereas high concentrations of delphinidin in combination with chlorophyll accounted for black pigmentation. Real-time PCR analysis of tissues that varied in pigmentation intensity due to varying anthocyanin concentration revealed functional but differentially expressed structural genes in the anthocyanin biosynthetic pathway. Transcript levels for genes encoding key enzymes were markedly reduced in tissues coincident with reduced anthocyanin concentration. Assessment of transcript levels for regulatory genes encoding MYC, MYB, and WD40 class transcription factors supports a model to explain variation in pigmentation whereby differential expression of these genes occurs within the framework of a coordinated transcription activator complex. Conservation of anthocyanin-related gene function across species is being evaluated via concurrent analysis of differential pigmentation in related Solanaceous crops including Petunia and eggplant. These studies will enable development of selection systems to control expression of anthocyanin-related structural genes. Control of regulatory gene expression will provide new opportunities to create plants with novel leaf, stem, and fruit colors.