Yasuyuki Yamaji, and
Department of Agricultural and Environmental Biology, Graduate School of Agricultural and Life Sciences, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo, 113-8657, Japan
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Accepted 26 April 2013.
Lectin-mediated resistance (LMR) has been suggested to comprise an uncharacterized branch of antiviral plant innate immunity. To unveil the feature of resistance conferred by jacalin-type lectin required for potexvirus resistance 1 (JAX1), a recently isolated LMR gene against potexviruses, we analyzed the resistance-breaking variants to find the viral component involved in resistance. We employed grafting-mediated inoculation, a high-pressure virus inoculation method, to obtain Potato virus X (PVX) variants that can overcome JAX1-mediated resistance. Whole-genome sequencing of the variants suggested that a single amino acid in the methyl transferase domain of the replicase encoded by PVX is responsible for this resistance-breaking property. Reintroduction of the amino-acid substitution to avirulent wild-type PVX was sufficient to overcome the JAX1-mediated resistance. These results suggest that viral replicase is involved in JAX1-mediated resistance. The residue that determines the resistance-breaking properties was highly conserved among potexviruses, suggesting a general role of the residue in potexvirus–JAX1 interactions.
© 2013 The American Phytopathological Society