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Title: Nb is a TIR-NLR innate immune receptor that requires EDS1 for induction of the hypersensitive response to the potato virus X movement protein

Author
item LI, FENG - Huazhong Agricultural University
item KAMEI, AYAKO - University Of California
item ZHANG, ZHONG-LIN - University Of California
item MARANO, MARISA ROSA - National University Of Rosario
item TUNG, JEFFREY - University Of California
item BAULCOMBE, DAVID - University Of Cambridge
item Baker, Barbara

Submitted to: PLoS Pathogens
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/30/2014
Publication Date: N/A
Citation: N/A

Interpretive Summary: Dominant plant resistance (R)-genes against viruses are needed for protection of major crops from virus diseases. Characterized resistance R-genes and viral effector proteins are needed to understand host resistance mechanisms to optimize plant defense against viruses.

Technical Abstract: Dominant plant resistance (R)-genes against viruses are needed for protection of major crops from virus diseases. Characterized resistance R-genes and viral effector proteins are needed to understand host resistance mechanisms to optimize plant defense against viruses. Of the many hundreds of resistance genes isolated, only a few confer virus resistance and only two TIR-NLR [Toll-interleukin1 receptor (TIR)-nucleotide binding-leucine rich repeat (NLR)] R-genes, N for tobamovirus tobacco mosaic virus (TMV) resistance and Y-1 for potyvirus potato virus Y (PVY) resistance have been isolated and characterized from the agronomically important Solanaceae family of plants. To address this need we isolated and characterized the potexvirus, potato virus X (PVX) resistance gene Nb from Solanum tuberosum using map-based cloning and comparative genome analysis. We show that Nb is an orthologue of the tomato bacterial resistance gene Bs4 and that the Nb protein is closely related to Bs4, N and Y-1 proteins. Nb specifically recognizes and triggers a hypersensitive response (HR) to the 25 kD movement protein (MP) of the PVX-UK1 strain but not the PVX-UK3 strain. We show that PVX-UK1 infected transgenic Nb-tobacco display a ten-fold reduced level of PVX RNA in systemic upper leaves one-week post infection compared to PVX infected wild type tobacco. We further show that Nb-mediated HR to PVX UK1 MP is dependent on EDS1. This work will facilitate breeding of PVX resistance into susceptible potato cultivars and provides a new and characterized host –virus system to understand the mechanisms of TIR-NLR- effector recognition, NLR activation, HR induction and host resistance to viruses in Solanaceae crops. This system is additionally important for understanding the evolutionary and functional interplay between NLR-mediated resistance and RNA silencing and the role of virus suppressors of RNA silencing in effector triggered NLR-mediated immunity.