XVI International Botanical Congess

Arabidopsis is used to dissect numerous developmental, biochemical and signal transduction pathways. However, with regard to nitrogen-fixing and VA-mycorrhizal symbioses, Arabidopsis is wanting. Brassicaceae and a few other families do not establish mycorrhizal associations. Moreover, nitrogen-fixing bacteria interact only with a limited number of species. In legumes, Nod- and Myc- co-segregate, strongly suggesting that the two symbioses share common elements. We found that early nodulin genes are expressed in legume VA-mycorrhizae, supporting the idea that the signal transduction pathways between the two symbioses are conserved. Now, we have analyzed the responses of 5 classes of non-nodulating Melilotus alba mutants to Glomus intraradices. We have also performed northern analysis to determine whether the sym mutations affect the induction of the ENOD genes.