Broad-spectrum polerovirus resistance conferred by a potato TIR-NLR immune receptor

Potato leafroll virus (PLRV) is an economically important viral disease of potato ( S. tuberosum ). Genetic resistance to this phloem-limited virus is rare, and no cloned resistance ( R ) genes have been reported. Rl _adg confers resistance to PLRV in an Andean potato landrace, LOP-868 (Velásquez et al. 2007). We identified the functional Rl _adg gene as a homolog of the tomato TIR-NLR-encoding Bs4 . Rl _adg interacts with the serine protease domain of the PLRV protein P1, which is essential for virus replication. This recognition is independent of the protease’s enzymatic activity, and the Rl _adg immune receptor oligomerizes upon direct association with the protease. Like PLRV, many poleroviruses contain a serine protease. Despite their diverse amino acid sequences, these proteases are predicted to share similar structures. Rl _adg recognizes all ten tested polerovirus proteases, suggesting a conserved structural recognition mechanism. We propose that Rl _adg ’s broad recognition capacity could enable resistance to poleroviruses in many crop species. Rl _adg is the first R -gene reported to confer resistance to a phloem-limited pathogen and could provide enhanced resistance to many economically important poleroviruses.