The R locus in maize-A versatile marker system for probing differential gene expression

The R locus is a key regulatory gene in the maize anthocyanin biosynthetic pathway. Extensive allelic diversity of R gene and tissue specific patterns of anthocyanin pigmentation governed by the Rgene and its displaced repeats (collectively termed as the R gene family) provide an ideal system for the analysis of differential regulation of gene expression. Elegant genetic experiments on R locus have enriched the understanding of tissue-specific gene expression and the regulation mechanisms in higher plants. The progress made in using the R gene as a marker system to study differential gene expression is reviewed here.