A characterization of candidate effector proteins in arbuscular mycorrhizal fungi
A. MACLEAN (1), H. Park (2), L. Mainzer (3), M. Hudson (4), V. Levesque-Tremblay (2) (1) Boyce Thompson Institute, U.S.A.; (2) Boyce Thompson Institute, U.S.A.; (3) University of Illinois at Urbana-Champaign, U.S.A.; (4) University of Illinois, Urbana-Champaign, U.S.A.

Arbuscular mycorrhizal symbiosis is established as the result of a complex signaling pathway that permits the growth of fungal hyphae through the epidermal cells of host plants, and the subsequent development of highly branched structures called arbuscules within the host cortical cells. We hypothesize that arbuscular mycorrhizal fungi (AMF) secrete effector proteins that act to modulate root cell biology and suppress host defense responses. Using a combination of genome and transcriptome data, we have compiled a list of 27 candidate AMF effectors encoded by Glomus versiforme, Gigaspora gigantea, and Rhizophagus irregularis. Expression analyses reveal that a majority of the genes encoding the putative effectors are expressed exclusively, or primarily, in the presence of a host plant (Medicago truncatula), supporting a role in mediating plant-microbe symbiosis. Subcellular localization assays with GFP-tagged proteins indicate that the majority of these proteins exhibit a nuclear/cytosolic distribution, however 5 candidates were localized to the host cell nucleus, suggesting a possible role in modulating gene expression. We have furthermore screened each candidate effector against a yeast two-hybrid library of M. truncatula transcription factors as a means of identifying interactions between our putative effectors and host proteins. Our data support the hypothesis that AMF employ effector proteins to facilitate plant-microbe interactions, and offer new insight into the roles these fungal effectors may play during symbiosis.

Abstract Number: P2-37
Session Type: Poster