A CHLOROPHYLL SYNTHETASE GENE FROM ARABIDOPSIS-THALIANA

During the course of an Arabidopsis thaliana genome sequencing project , we identified a gene, G4, with a derived amino acid sequence showing homology to the product of the Rhodobacter capsulatus bchG locus whic h is involved in the esterification of bacterio-chlorophyllide with ge ranylgeraniol. The relationship between this gene and bchG was confirm ed by the isolation and analysis of a corresponding full-length cDNA. Comparison of genomic and cDNA sequences indicated that the gene is ma de up of 14 exons, some of them being very short. Southern and Norther n analyses showed that this sequence represents a single-copy gene and its transcript is detected only in green or greening tissues. Both ho mologies and expression data suggest that this gene encodes a chloroph yll synthetase, one of the last enzymes of chlorophyll biosynthesis, a nd thus represents a new example of a nuclear gene encoding an enzyme of this pathway in higher plants.