2 AMIDOPHOSPHORIBOSYLTRANSFERASE GENES OF ARABIDOPSIS-THALIANA EXPRESSED IN DIFFERENT ORGANS

Amidophosphoribosyltransferase (ATase: EC 2.4.2.14) is a key enzyme in the pathway of purine nucleotide biosynthesis. We have identified sev eral cDNA clones whose amino acid sequences exhibit similarity with th e known ATases in a cDNA library of young floral buds of Arabidopsis t haliana. The cDNA clones are derived from two genes homologous with ea ch other. These cDNAs represent the first plant representatives of ATa se gene. Structural comparison with ATases of other organisms has reve aled that the two genes encode [4Fe-4S] cluster-dependent ATases. Nort hern blot analysis showed that expression level of the genes is differ ent in three organs; one gene is expressed in flowers and roots, while the other gene is mainly expressed in leaves.