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A Replicase of Potato virus X Acts as the Resistance-Breaking Determinant for JAX1-Mediated Resistance

September 2013 , Volume 26 , Number  9
Pages  1,106 - 1,112

Kyoko Sugawara, Takuya Shiraishi, Tetsuya Yoshida, Naoko Fujita, Osamu Netsu, Yasuyuki Yamaji, and Shigetou Namba

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