title: Medicago truncatula syntaxin SYP132 defines the symbiosome membrane and infection droplet membrane in root nodules.
abstract: Symbiotic association of legume plants with rhizobia bacteria culminates in organogenesis of nitrogen-fixing root nodules. In indeterminate nodules, plant cells accommodate rhizobial infection by enclosing each bacterium in a membrane-bound, organelle-like compartment called the symbiosome. Numerous symbiosomes occupy each nodule cell; therefore an enormous amount of membrane material must be delivered to the symbiosome membrane for its development and maintenance. Protein delivery to the symbiosome is thought to rely on the plant secretory system; however, the targeting mechanisms are not well understood. In this study, we report the first in-depth analysis of a syntaxin localized on symbiosome membranes. Syntaxins help define a biochemical identity to each compartment in the plant secretory system and facilitate vesicle docking and fusion. Here, we present biochemical and cytological evidence that the SNARE MtSYP132, a Medicago truncatula homologue of Arabidopsis thaliana Syntaxin of Plants 132, localizes to the symbiosome membrane. Using a specific anti-MtSYP132 peptide antibody, we also show that MtSYP132 localizes to the plasma membrane surrounding infection threads and is most abundant on the infection droplet membrane. These results indicate that MtSYP132 may function in infection thread development or growth and the early stages of symbiosome formation.
authors.affiliation: Department of Plant and Soil Sciences, University of Delaware, Newark, DE 19717, USA.
authors.forename: Christina M
authors.initials: CM
authors.lastname: Catalano
authors.forename: Kirk J
authors.initials: KJ
authors.lastname: Czymmek
authors.forename: Janine G
authors.initials: JG
authors.lastname: Gann
authors.forename: D Janine
authors.initials: DJ
authors.lastname: Sherrier
mesh_terms: D000595:Amino Acid Sequence; D001483:Base Sequence; D018506:Gene Expression Regulation, Plant; D007150:Immunohistochemistry; D046913:Medicago truncatula / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism*; D050765:Qa-SNARE Proteins / Q000235:genetics / Q000378:metabolism*; D053204:Root Nodules, Plant / Q000235:genetics / Q000378:metabolism*; D013559:Symbiosis / Q000235:genetics / Q000502:physiology
chemical_list: D010940:Plant Proteins; D050765:Qa-SNARE Proteins