ISOLATION OF CDNAS ENCODING 2 PURINE BIOSYNTHETIC-ENZYMES OF SOYBEAN AND EXPRESSION OF THE CORRESPONDING TRANSCRIPTS IN ROOTS AND ROOT-NODULES

Soybean nodule cDNA clones encoding glycinamide ribonucleotide (GAR) s ynthetase (GMpurD) and GAR transformylase (GMpurN) were isolated by co mplementation of corresponding Escherichia coli mutants. GAR synthetas e and GAR transformylase catalyse the second and the third steps in th e de novo purine biosynthesis pathway, respectively. One class of GAR synthetase and three classes of GAR transformylase cDNA clones were id entified. Northern blot analysis clearly shows that these purine biosy nthetic genes are highly expressed in young and mature nodules but wea kly expressed in roots and leaves. Expression levels of GMpurD and GMp urN mRNAs were not enhanced when ammonia was provided to non-nodulated roots.