GENETIC-ANALYSIS OF CHLOROPHYLL BIOSYNTHESIS

During this decade, there have been major advancements in the understa nding of genetic loci involved in synthesis of the family of Mg-tetrap yrroles known as chlorophylls and bacteriochlorophylls. Molecular gene tic analysis of Mg-tetrapyrrole biosynthesis was initiated by the perf ormance of detailed sequence and mutational analysis of the photosynth esis gene cluster from Rhodobacter capsulatus. These studies provided the first detailed understanding of genes involved in bacteriochloroph yll a biosynthesis. In the short time since these studies were initiat ed, most of the chlorophyll biosynthesis genes have been identified by virtue of their ability to complement bacteriochlorophyll a biosynthe sis mutants as well as by sequence homology comparisons. This review i s centered on a discussion of our current understanding of bacterial, algal, and plant genes that code for enzymes in the Mg-branch of the t etrapyrrole biosynthetic pathway that are responsible for synthesis of chlorophylls and bacteriochlorophylls.