Molecular cloning and expression analysis of the mevalonate kinase gene from Arabidopsis thaliana

Mevalonate kinase (MVK), the enzyme that catalyzes the phosphorylation of m evalonate to produce mevalonate 5-phosphate, is considered as a potential r egulatory enzyme of the isoprenoid biosynthetic pathway. The Arabidopsis th aliana MVK gene corresponding to the MVK cDNA previously isolated has been cloned and characterized. RNAse protection analysis indicated that the expr ession of the MVK gene generates three mRNA populations with 5' ends mappin g 203, 254 and 355 nt upstream of the MVK ATG start codon. Northern blot an alysis showed that the MVK mRNA accumulates preferentially in roots and inf lorescences. Histochemical analysis, with transgenic A. thaliana plants con taining a translational fusion of a 1.8 kb fragment of the 5' region of the MVK gene to the beta-glucuronidase (GUS) reporter gene, indicated that the MVK 5'-flanking region directs widespread expression of the GUS gene throu ghout development, although the highest levels of GUS activity are detected in roots (meristematic region) and flowers (sepals, petals, anthers, style and stigmatic papillae). The expression pattern of the MVK gene suggests t hat the role of the encoded MVK is the production of a general pool of meva lonate-5-phosphate for the synthesis of different classes of isoprenoids in volved in both basic and specialized plant cell functions. Functional promo ter deletion analysis in transfected A. thaliana protoplasts indicated that regulatory elements between positions -295 and -194 of the MVK 5'-flanking region are crucial for high-level MVK gene expression.