Abstract
In bacteria and mammals, guanylate kinase (Gmk) is known to be a central enzyme for guanine nucleotide metabolism, phosphorylating (d)GMP to (d)GDP, and is implicated in the regulation of the supply of guanine nucleotides to cell signaling pathways. However, little is known about enzymatic and signaling role of Gmk in higher plants. The rice virescent-2 (v2) mutant is altered in chloroplast differentiation and develops chloroplast-deficient leaves. Previously we cloned V2 gene and revealed that V2 gene (designated as mGmk) encodes a mitochondria-localized Gmk. While there are many reports of cytosolic Gmk in eukaryotes, much less is known of the mitochondrial Gmk. Our data indicate that the Gmk activity in mitochondria is essential for chloroplast development. Rice has been reported to have another Gmk gene (ogk1). Through the comparison of these two Gmk genes, the functional significance of mGmk in mitochondria will be discussed.
