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

Abstract

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. Rladg confers resistance to PLRV in an Andean potato landrace, LOP-868 (Velasquez et al. 2007). We identified the functional Rladg gene as a homolog of the tomato TIR-NLR-encoding Bs4. Rladg interacts with the serine protease domain of the PLRV protein P1, which is essential for virus replication. This recognition is independent of the proteases enzymatic activity, and the Rladg 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. Rladg recognizes all ten tested polerovirus proteases, suggesting a conserved structural recognition mechanism. We propose that Rladgs broad recognition capacity could enable resistance to poleroviruses in many crop species. Rladg is the first R-gene reported to confer resistance to a phloem-limited pathogen and could provide enhanced resistance to many economically important poleroviruses.