GENETIC-EVIDENCE FOR THE OCCURRENCE OF ASSIMILATORY NITRATE REDUCTASEIN ARBUSCULAR MYCORRHIZAL AND OTHER FUNGI

Using primers synthesized from two conserved regions and employing PCR , a DNA segment coding for part of the apoprotein of assimilatory nitr ate reductase could be amplified from the fungi Aspergillus nidulans, Pythium intermedium, Phytophthora infestans, Phytophthora megasperma a nd Glomus D13. Sequencing of the amplificates as well as DNA hybridiza tion revealed strong homologies with the nitrate reductase gene in all cases. The dioxigenin-labeled amplificate from Glomus hybridized with DNA isolated from Glomus spores. The data from these gene probing exp eriments are generally in accord with the published results from enzym e measurements. Thus assimilatory nitrate reductase occurs in saprophy tic, parasitic as well as arbuscular mycorrhizal fungi. No amplificate s with these primers were obtained with DNA isolated from Mucor mucedo and Saprolegnia ferax. Such results agree with the failure to detect nitrate assimilation physiologically in these two organisms.