A host signal to microbe-plant interface for the establishment of symbiosis
O. OZTAS (1), T. He (2), H. Pan (1), E. Limpens (3), E. Federova (3), T. Bisseling (3), M. Roberts (2), D. Wang (4) (1) University of Massachusetts Amherst, U.S.A.; (2) Boston College, U.S.A.; (3) Wageningen University, Netherlands; (4) University of Massachusetts Amherst, U.S.A.

Legumes enter a symbiotic interaction with rhizobia, soil bacteria that converts atmospheric nitrogen into usable ammonia. In root nodules, bacteria are internalized by host plant cells inside an intracellular compartment called the symbiosome and morphologically differentiate into nitrogen-fixing forms. We showed that the SYNTAXIN 132 (SYP132) gene in the model legume Medicago truncatula undergoes alternative cleavage and polyadenylation during transcription, giving rise to two t-SNARE protein isoforms. One of the isoforms, SYP132A, is a component of a nodule-specific secretory pathway required for the delivery of host proteins to the symbiosome (1, 2). Among the host proteins targeted to the symbiosome is DNF2 (2). DNF2 is specifically expressed in nodules following bacterial infection and is essential for bacteria to survive inside host cell. We discovered that DNF2 belongs to a novel class of phosphatidylinositol-specific phospholipase C (PI-PLC) that cleaves proteins containing glycophosphatidylinositol (GPI), a glycolipid that is attached to the C-terminus of a protein to anchor the protein on cell membranes. We hypothesize that DNF2 cleaves certain GPI-anchored proteins, the release of which from the symbiosome membrane is essential to avoid defense responses that would otherwise eliminate bacteria from the host cell. During the establishment of symbiosis between legumes and rhizobia, the activity of DNF2 marks bacteria inside symbiosome as an ally, not an enemy. We will provide the latest result supporting our hypothesis.

Abstract Number: P2-42
Session Type: Poster