27] Cloning of carotenoid biosynthetic genes from maize

Abstract

This chapter discusses the strategy and methods used to isolate carotenoid biosynthetic genes in maize. These strategies and methods can be applied to any plant containing an endogenous or introduced transposon system. Several genes have been cloned from maize by a strategy commonly referred to as “transposon tagging.” For this cloning strategy, a transposon is used to induce a mutation in a gene of interest. Several genes involved in carotenoid biosynthesis have been identified in maize. Mutants of these genes exhibit white to pale-yellow kernel and typically albino seedling phenotypes. The biochemical analysis of these mutants has shown that they accumulate intermediates in the carotenoid biosynthetic pathway. Therefore, these mutants are probably deficient in one or more of the enzymes responsible for the biosynthesis of carotenoids. Transposon-induced mutant alleles of several carotenoid biosynthetic genes have been produced in maize. In addition, other maize genes have been characterized that have a tissue-specific pattern of carotenoid expression; and therefore, genes may be involved in the regulation of carotenoid biosynthesis. One such gene, the y1 gene, has been cloned using a transposon tagging and cloning strategy.