title: The cyst nematode SPRYSEC protein RBP-1 elicits Gpa2- and RanGAP2-dependent plant cell death.
abstract: Plant NB-LRR proteins confer robust protection against microbes and metazoan parasites by recognizing pathogen-derived avirulence (Avr) proteins that are delivered to the host cytoplasm. Microbial Avr proteins usually function as virulence factors in compatible interactions; however, little is known about the types of metazoan proteins recognized by NB-LRR proteins and their relationship with virulence. In this report, we demonstrate that the secreted protein RBP-1 from the potato cyst nematode Globodera pallida elicits defense responses, including cell death typical of a hypersensitive response (HR), through the NB-LRR protein Gpa2. Gp-Rbp-1 variants from G. pallida populations both virulent and avirulent to Gpa2 demonstrated a high degree of polymorphism, with positive selection detected at numerous sites. All Gp-RBP-1 protein variants from an avirulent population were recognized by Gpa2, whereas virulent populations possessed Gp-RBP-1 protein variants both recognized and non-recognized by Gpa2. Recognition of Gp-RBP-1 by Gpa2 correlated to a single amino acid polymorphism at position 187 in the Gp-RBP-1 SPRY domain. Gp-RBP-1 expressed from Potato virus X elicited Gpa2-mediated defenses that required Ran GTPase-activating protein 2 (RanGAP2), a protein known to interact with the Gpa2 N terminus. Tethering RanGAP2 and Gp-RBP-1 variants via fusion proteins resulted in an enhancement of Gpa2-mediated responses. However, activation of Gpa2 was still dependent on the recognition specificity conferred by amino acid 187 and the Gpa2 LRR domain. These results suggest a two-tiered process wherein RanGAP2 mediates an initial interaction with pathogen-delivered Gp-RBP-1 proteins but where the Gpa2 LRR determines which of these interactions will be productive.
authors.affiliation: Boyce Thompson Institute for Plant Research, Ithaca, New York, USA.
authors.forename: Melanie Ann
authors.initials: MA
authors.lastname: Sacco
authors.forename: Kamila
authors.initials: K
authors.lastname: Koropacka
authors.forename: Eric
authors.initials: E
authors.lastname: Grenier
authors.forename: Marianne J
authors.initials: MJ
authors.lastname: Jaubert
authors.forename: Alexandra
authors.initials: A
authors.lastname: Blanchard
authors.forename: Aska
authors.initials: A
authors.lastname: Goverse
authors.forename: Geert
authors.initials: G
authors.lastname: Smant
authors.forename: Peter
authors.initials: P
authors.lastname: Moffett
mesh_terms: D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D000818:Animals; D016923:Cell Death / Q000502:physiology; D020690:GTPase-Activating Proteins / Q000378:metabolism*; D015801:Helminth Proteins / Q000235:genetics / Q000378:metabolism; D006967:Hypersensitivity; D008969:Molecular Sequence Data; D018515:Plant Leaves / Q000378:metabolism; D010940:Plant Proteins / Q000378:metabolism*; D017863:Potexvirus / Q000235:genetics; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D012641:Selection, Genetic; D016415:Sequence Alignment; D014026:Nicotiana / Q000378:metabolism; D014431:Tylenchoidea / Q000235:genetics / Q000378:metabolism*
chemical_list: D020690:GTPase-Activating Proteins; D015801:Helminth Proteins; D010940:Plant Proteins; D011993:Recombinant Fusion Proteins