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

Abstract

The discovery of the 2-C-methyl-d-erythritol-4-phosphate pathway for the biosynthesis of isoprenoids raises the important question of the nature and regulation of the enzymes involved in this pathway. CLA1, a gene previously isolated from Arabidopsis, encodes the first enzyme of the 2-C-methyl-d-erythritol-4-phosphate pathway, 1-deoxy-d-xylulose-5-phosphate synthase. We demonstrate this enzyme activity by complementation of the cla1-1 mutant phenotype and by direct enzymatic assays. Based on mRNA and protein expression patterns this enzyme is expressed mainly in developing photosynthetic and non-photosynthetic tissues. The ␤-glucuronidase expression pattern driven from the CLA1 gene regulatory region supports the northern and protein data while also showing that this gene has some level of expression in most tissues of the plant. A mutation in the CLA1 gene interferes with the normal development of chloroplasts and etioplasts, but does not seem to affect amyloplast structure. Microscopic analysis also shows a pleiotropic effect of the CLA1 gene mutation in mesophyll tissue formation.In higher plants isoprenoids are derived from isopentenyl diphosphate (IPP) and synthesized in at least two different compartments, the cytoplasm and the chloroplast. For a long time it was assumed that IPP was synthesized exclusively by the mevalonate pathway in all organisms (Spurgeon and Porter, 1981; Goldstein and Brown, 1990). However, independent studies have demonstrated that in eubacteria, green algae, and plants, IPP is also synthesized by a non-mevalonate pathway designated as the 2-Cmethyl-d-erythritol-4-P (MEP) pathway (for review, see Rohmer, 1998Rohmer, , 1999Lichtenthaler, 1999). Thus in plants cytosolic IPP is synthesized by the mevalonate pathway and plastidic IPP is synthesized by the MEP pathway (Lichtenthaler, 1999). In the MEP pathway IPP is synthesized from pyruvate and glyceraldehyde-3-P via novel intermediates (Rohmer et al

Disruption of the 1-deoxy-D-xylulose-5-phosphate reductoisomerase (DXR) gene results in albino, dwarf and defects in trichome initiation and stomata closure in Arabidopsis

“…Like the other albino mutants of the enzymes involved in MEP-related biosynthetic pathways, the dxr mutants exhibited an arrest in plastid development at early stages [20,22,30,[46][47][48]. This is consistent with the increased chlorophyll a/ b ratio observed in the pale inflorescence tissues, which are more sensitive to light due to the undeveloped plastids [49].…”

“…In this pathway, DXS has been identified to catalyze the first step, the key step of the MEP pathway, in Arabidopsis [22,47,58]. DXS was also found to share a similar expression pattern with DXR, and both DXS and DXR null mutants displayed an [7,19,22,47]. Many studies on comparisons between DXR and DXS have also been carried out [7,19].…”

Disruption of phytoene desaturase gene results in albino and dwarf phenotypes in Arabidopsis by impairing chlorophyll, carotenoid, and gibberellin biosynthesis

“…These genes include CLA1 [30], IPI, GGPS, PSY, ZDS and LYC that are directly involved in the carotenoid biosynthesis pathway, GGRS that is required in the side-branched chlorophyll biosynthesis, and PDS1 and IM that are functionally related to phytoene desaturation. The results showed that the nine genes shared a similar pattern of expression.…”

The Arabidopsis immutans Mutation Affects Plastid Differentiation and the Morphogenesis of White and Green Sectors in Variegated Plants

“…Identification of this type of communication has come from an examination of a handful of nuclear gene-induced pigment mutants whose white leaf tissues have abnormal plastids and cells, and altered palisade and/or spongy mesophyll cell layer organizations. These include dag of Antirrhinum majus (Chatterjee et al, 1996), dcl of tomato (Keddie et al, 1996), and several Arabidopsis mutants, including cla1 (Mandel et al, 1996;Estévez et al, 2000), cue1 (Li et al, 1995;Streatfield et al, 1999), and pac (Reiter et al, 1994;Meurer et al, 1998). Because the products of the genes defined by these mutations reside in the plastid, it has been argued that these proteins are not independently required for plastid development and cell differentiation (and consequently for proper leaf morphogenesis), but that the effects on mesophyll cell differentiation are a consequence of incomplete chloroplast differentiation.…”