Poster: Plant-symbiont interactions

Abs # 585: Medicago truncatula DMI1 required for bacterial and fungal symbioses in legumes

Presenter:	Riely, Brendan K, bkriely@ucdavis.edu
Authors	Riely, Brendan K (A)   Ané, Jean-Michel  (A)   Cook, Doug R (A)
Affiliations:	(A): University of California-Davis Department of Plant Pathology

Leguminous plants can enter a nitrogen-fixing symbiosis with soil bacteria called rhizobia. Plant perception of rhizobial “Nod Factors” facilitates bacterial entry and initiates a program that culminates in the development of a root nodule. Understanding how this symbiosis develops is an important biological question that is particularly relevant in modern agriculture. Our group is utilizing the model legume Medicago truncatula to unravel the early molecular processes regulating nodulation. Previous mutant screens identified genes that are essential for nodulation. The dmi1 (doesn’t make infections) mutant does not associate with either rhizobia or arbuscular mycorrhizal fungi indicating that the signaling pathways leading to these symbioses share common components. Nod factors elicit a rapid ion flux in dmi1 mutants, as with wild-type plants, but do not elicit “calcium spiking”, cortical cell division, or early nodulin (ENOD) gene expression. We have cloned DMI1 and found that it encodes a novel protein sharing some homologies with ligand-gated cation channels from prokaryotes. DMI1 is ubiquitous among members of the plant kingdom but is absent from animals and fungi. Homologies with prokaryotic channels suggest that DMI1 may regulate the ion fluxes that occur early in the symbiotic interaction. We are currently characterizing the expression, the biochemical structure and function of DMI1 and are investigating its association with other proteins. Current progress will be reported.