ASGSB 1999 Annual Meeting Abstracts

COMPARISON OF ANTHOCYANIN PRODUCTION IN THE AUXIN-INSENSITIVE DGT MUTANT AND IN WILD TYPE TOMATOES. M.S. Rice, J. Butz, L. Higgins, D. Hodgson, and J. Snowbarger. Department of Chemistry and Biochemistry, Calif. Polytechnic State Univ., San Luis Obispo.

The diageotropica (dgt) mutation is a single gene mutation that confers resistance to auxin, and therefore produces a number of phenotypic aberrations. One of the most important changes is an alteration in responses to gravity. Young dgt seedlings respond slowly but completely to gravity, while older dgt plants grow horizontally. Dgt seedlings also have higher levels of anthocyanins (purple pigments) than wild type plants. Recent studies suggest that the dgt mutation alters the transcription of some auxin-regulated genes, which may include genes for anthocyanin biosynthesis.

To better understand the role of auxin in gene regulation, and to elucidate the alteration in auxin perception in dgt, we are examining the transcription and activity of the initial genes in the anthocyanin biosynthesis pathway. The transcription and activity of the enzymes phenylalanine ammonia lyase (PAL) and chalcone synthase (CHS), the first two steps in anthocyanin biosynthesis, are compared in dgt and wild type seedlings.

Dark-grown 7 day old seedlings are irradiated with red light for varying lengths of time. RNA and proteins are extracted, and northern blots and enzyme activity assays of crude hypocotyl protein preparations will be used to determine the amount of transcription and the activity of the PAL and CHS enzymes. This will help to determine the effect of auxin on anthocyanin biosynthesis and increase our understanding of auxin function.

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