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Title: TRANSCRIPTION FACTOR FAMILIES REGULATE THE ANTHOCYANIN BIOSYNTHETIC PATHWAY IN CAPSICUM

Author
item LIGHTBOURN, GORDON - VPI AND STATE UNIV
item WINKEL, BRENDA - VPI AND STATE UNIV
item GRIESBACH, ROBERT - USDA, ARS
item Stommel, John

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 3/21/2008
Publication Date: 4/23/2008
Citation: Lightbourn, G., Winkel, B., Griesbach, R., Stommel, J.R. 2008. Transcription factor families regulate the anthocyanin biosynthetic pathway in capsicum. Meeting Abstract.

Interpretive Summary:

Technical Abstract: Pigmentation in flowers, fruits and foliage enhances visual appeal and nutritive value of plants. Color is attributed to several pigments, including the chlorophylls, carotenoids, flavonoids and betalains. The colored anthocyanins are a subgroup of the flavonoids, and in Capsicum (pepper) are expressed as violet to black pigmentation (delphinidins) in fruits, foliage, and floral tissue. Utilizing novel pepper pigment mutants, we identified key steps that regulate the genetic control of tissue-specific anthocyanin accumulation. Using real-time PCR we evaluated expression of structural genes in the anthocyanin biosynthetic pathway and regulatory genes that influence structural gene expression in flowers, fruits and leaves from contrasting genotypes (purple flower/black fruit and leaf vs. white flower/green fruit and leaf). The structural genes evaluated included Chs (chalcone synthase), Dfr (dihydroflavonol reductase) and Ans (anthocyanin synthase) which corresponded to early, middle and terminal points in the biosynthetic pathway. Transcript level of all three structural genes was significantly greater in flower, fruit and leaf tissue from purple/black tissue of the anthocyanin accumulating genotype. We also evaluated expression of regulatory genes (Myb, Myc, and Wd40) that comprise a transcription factor complex. Transcript levels of Myb and Myc were higher in flowers and fruit of the pigmented genotype, but not in leaves. No differential regulation was observed for Wd40. Sequence analysis revealed identical 962 bp Myb cDNAs in anthocyanin pigmented flowers, fruits and leaves. A single non-functional 1112 bp Myb cDNA was present in white flowers. Three Myb genomic DNAs were identified from the pigmented genotype and differed by one or two intronic regions, indicating occurrence of a Myb gene family. Sequence analysis of the 5’ UTR confirmed occurenceoccurrence of a gene family. Myc sequence analysis also revealed multiple cDNAs. However, these cDNA differed at their polyadenylation sites, suggesting that a single gene encodes these cDNA, and that alternate splicing may account for observed differences. Our results indicate that different mechanisms contribute to the regulation of anthocyanin biosynthesis in different parts of the Capsicum plant. .mi-RNA is proposed as an alternate method of regulation in leaf tissue and is currently being evaluated.