Poster: Plant Pathogen/Symbiont Interactions

Abs # 696: Proteomic analysis of the symbiosome membrane from Medicago truncatula root nodules

Presenter:	Catalano, Christina M., 07850@udel.edu
Authors	Catalano, Christina M. (A)   Sherrier, D. Janine (A)
Affiliations:	(A): University of Delaware Department of Plant and Soil Sciences

Nitrogen fixing root nodules result from the symbiotic relationship between rhizobia and legume host plants. Within mature nitrogen fixing root nodules, a plant-derived membrane called the symbiosome membrane encloses the bacteria. This membrane is formed from the plasma membrane and becomes specialized during nodule development. The membrane serves both structural and functional roles, most importantly separating the bacteria from the plant cell cytoplasm and controlling metabolite exchange between the partners. To better understand symbiosome membrane formation and function, we are using proteomics to identify proteins that facilitate the biochemical specialization of this membrane along with exploring how these proteins are targeted to the membrane. Standard subcellular fractionation and 2D-SDS PAGE followed by tandem mass spectroscopic analysis resulted in the identification of approximately 50 putative symbiosome membrane proteins. These putative symbiosome membrane proteins mainly represent housekeeping proteins including BiP, HSP70 and other chaperone proteins. Additional putative symbiosome membrane proteins identified in this study include a multifunctional aquaporin, PDI, ENOD16, nodulin 25, and a protein important in protein targeting and trafficking. We are also confirming the subcellular location of a selected number of these proteins identified in our proteomic studies using immunolabeling and electron microscopy. These findings have important implications in better understanding the biochemical composition of the symbiosome membrane and may give insight into how proteins are targeted to this membrane.