NITROGEN-METABOLISM IN ACTINORHIZAL NODULES OF ALNUS-GLUTINOSA - EXPRESSION OF GLUTAMINE-SYNTHETASE AND ACETYLORNITHINE TRANSAMINASE

Two nodule cDNA clones representing genes involved in Alnus glutinosa nitrogen metabolism were analysed. ag11 encoded glutamine synthetase ( GS), the enzyme responsible for ammonium assimilation, while ag118 enc oded acetylornithine transaminase (AOTA), an enzyme involved in the bi osynthesis of citrulline, the nitrogen transport form in Alnus. GS mRN A was found at highest levels in root nodules, where it was present in the infected cells as well as in the cells of the pericycle of the va scular system. AOTA transcripts were found at high levels in nodules, confined to the infected cells, suggesting that in nodules of A. gluti nosa, citrulline biosynthesis takes place mainly in the infected cells .