Transposon tagging is a very powerful approach for isolating genetic loci encoding unknown products. This approach will be used to isolate maize and tomato genes involved in the carotenoid biosynthetic pathway. Carotenoids are pigments which play an important role in photoprotection in plants. Carotenoids are also essential in humans and animals as precursors of vitamin A and protective agents against photosensitive reactions. Carotenoid biosynthesis is fairly well understood from the biochemical analysis of many carotenoid mutants. A carotenoid mutant in maize, vp-5, and a carotenoid mutant in tomato, ghost, accumulate the same carotenoid precursor, phytoene. In order to initiate studies of gene regulation and expression, the maize vp-5 locus will be cloned by transposon tagging. Although transposable elements have not been discovered in tomato, we will attempt to introduce the cloned maize transposable element into tomato on engineered T-DNA vectors to be transmitted by infection with Agrobacterium. Transpositions into the tomato ghost locus will be selected and used for cloning of the gene.
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