An oomycete effector targets a plant RNA helicase involved in root development and defense

Laurent Camborde (1) , Andrei Kiselev (2) , Michiel Pel (2) , Aurélie Le Ru (3) , Alain Jauneau (3) , Cécile Pouzet (3) , Bernard Dumas (1) , Elodie Gaulin (1)

1 Interactions Microbiennes dans la Rhizosphère et les Racines
2 LRSV - Laboratoire de Recherche en Sciences Végétales
3 Plateforme TRI FR-AIB

Oomycete plant pathogens secrete effector proteins to promote disease. The damaging soilborne legume pathogen Aphanomyces euteiches harbors a specific repertoire of Small Secreted Protein effectors (AeSSPs), but their biological functions remain unknown. Here we characterize AeSSP1256. The function of AeSSP1256 is investigated by physiological and molecular characterization of Medicago truncatula roots expressing the effector. A potential protein target of AeSSP1256 is identified by yeast-two hybrid, co-immunoprecipitation, and fluorescent resonance energy transfer-fluorescence lifetime imaging microscopy (FRET-FLIM) assays, as well as promoter studies and mutant characterization. AeSSP1256 impairs M. truncatula root development and promotes pathogen infection. The effector is localized to the nucleoli rim, triggers nucleoli enlargement and downregulates expression of M. truncatula ribosome-related genes. AeSSP1256 interacts with a functional nucleocytoplasmic plant RNA helicase (MtRH10). AeSSP1256 relocates MtRH10 to the perinucleolar space and hinders its binding to plant RNA. MtRH10 is associated with ribosome-related genes, root development and defense. This work reveals that an oomycete effector targets a plant RNA helicase, possibly to trigger nucleolar stress and thereby promote pathogen infection.

Mots clés: Aphanomyces; effectors; Medicago; MtRH10; nucleolar stress; oomycete; plant development

Domaines: Biologie végétale

Laurent Camborde, Andrei Kiselev, Michiel Pel, Aurélie Le Ru, Alain Jauneau, et al.. An oomycete effector targets a plant RNA helicase involved in root development and defense. New Phytologist, In press, 233 (5), 17 p. ⟨10.1111/nph.17918⟩. ⟨hal-03526438⟩