Analysis of the expression of CLA1, a gene that encodes the 1-deoxyxylulose 5-phosphate synthase of the 2-C-methyl-D-erythritol-4-phosphate pathway in Arabidopsis

The discovery of the 2-C-methyl-D-erythritol-4-phosphate pathway for the bi osynthesis of isoprenoids raises the important question of the nature and r egulation of the enzymes involved in this pathway. CLA1, a gene previously isolated from Arabidopsis, encodes the first enzyme of the 2-C-methyl-d-ery thritol-4-phosphate pathway, 1-deoxy-d-xylulose-5-phosphate synthase. We de monstrate this enzyme activity by complementation of the cla1-1 mutant phen otype and by direct enzymatic assays. Based on mRNA and protein expression patterns this enzyme is expressed mainly in developing photosynthetic and n on-photosynthetic tissues. The beta-glucuronidase expression pattern driven from the CLA1. gene regulatory region supports the northern and protein da ta while also showing that this gene has some level of expression in most t issues of the plant. A mutation in the CLA1 gene interferes with the normal development of chloroplasts and etioplasts, but does not seem to affect am yloplast structure. Microscopic analysis also shows a pleiotropic effect of the CLA1 gene mutation in mesophyll tissue formation.