Glycine-Rich RNA-Binding Protein 7 interacts with and potentiates effector-induced immunity by Gpa2 and Rx1 based on an intact RNA Recognition Motif

SUMMARY The activity of intracellular plant Nucleotide-Binding Leucine-Rich Repeat (NB-LRR) immune receptors is fine-tuned by interactions between the receptors and their partners. Identifying NB-LRR interacting proteins is, therefore, crucial to advance our understanding of how these receptors function. A Co-Immunoprecipitation/Mass-Spectrometry screening was performed in Nicotiana benthamiana to identify host proteins associated with the Gpa2 CC-NB-LRR, which confers resistance against the potato cyst nematode Globodera pallida . A combination of biochemical, cellular, and functional assays was used to assess the role of a candidate interactor in defence. A N. benthamiana homolog of the Glycine-Rich RNA-Binding Protein 7 ( Nb GRP7) protein was prioritized as a novel Gpa2-interacting protein for further investigations. Nb GRP7 also associates in planta with the homologous Rx1 receptor, which confers immunity to Potato Virus X. We show that Nb GRP7 positively regulates extreme resistance by Rx1 and cell death by Gpa2. Mutating the Nb GRP7 RNA recognition motif compromises its role in Rx1-mediated defence. Strikingly, ectopic Nb GRP7 expression impacts the steady-state levels of Rx1, which relies on an intact RNA recognition motif. Combined, our findings illustrate that Nb GRP7 is a novel pro-immune component in effector-triggered immunity by regulating Gpa2/Rx1 functioning at a post-transcriptional level.