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.