Functional characterization of 29D09 effectors from the potato cyst nematode Globodera rostochiensis

60 pagesPlant-parasitic cyst nematodes penetrate root tissues of host plants and secrete effector proteins into host cells to establish successful parasitism. The Gr29D09 effector family from the potato cyst nematode Globodera rostochiensis is exclusively expressed in the nematode’s dorsal gland cell and is comprised of at least 27 variants. Constitutive expression of one of these variants, Gr29D09-V3, in potato has previously been shown to increase susceptibility to both G. rostochiensis and common scab (Streptomyces scabies). In this thesis, five representative Gr29D09 variants, V1, V3, A2, F10 and OA3, were selected for functional characterization. Plant immunity assays performed in Nicotiana benthamiana showed that all five variants suppressed flg22-triggered ROS production as well as the hypersensitive response (HR) induced by Gpa2/RBP-1 and Rx/CP. A co-immunoprecipitation-coupled with nanoLC-MS/MS approach identified mitochondria-associated StHXK7 as a specific interactor with Gr29D09-V3, a result confirmed with bimolecular fluorescence complementation assays. Elevated levels of StHXK7 mRNA were observed both in G. rostochiensis-infected potato roots and in transgenic potato plants expressing Gr29D09-V3. Localization of StHXK7 expression with a StHXK7promoter:GUS reporter line further revealed that StHXK7 was upregulated at the nematode-feeding site and its surrounding tissue. Lastly, StHXK7 was found to inhibit flg22-triggered ROS production in N. benthamiana. These data collectively support a model in which Gr29D09-V3 suppresses flg22-triggered ROS production through enhancing accumulation of StHXK7 mRNA and/or physically interacting with and stabilizing StHXK7 on mitochondria of plant cells