The Pik - p resistance to Magnaporthe oryzae in rice is mediated by a pair of closely linked CC-NBS-LRR genes

The blast resistance gene Pik - p , mapping to the Pik locus on the long arm of rice chromosome 11, was isolated by map-based in silico cloning. Four NBS-LRR genes are present in the target region of cv. Nipponbare, and a presence/absence analysis in the Pik - p carrier cv. K60 excluded two of these as candidates for Pik - p. The other two candidates ( KP3 and KP4 ) were expressed in cv. K60. A loss-of-function experiment by RNAi showed that both KP3 and KP4 are required for Pik - p function, while a gain-of-function experiment by complementation test revealed that neither KP3 nor KP4 on their own can impart resistance, but that resistance was expressed when both were introduced simultaneously. Both Pikp - 1 ( KP3 ) and Pikp - 2 ( KP4 ) encode coiled-coil NBS-LRR proteins and share, respectively, 95 and 99% peptide identity with the two alleles, Pikm1 - TS and Pikm2 - TS . The Pikp - 1 and Pikp - 2 sequences share only limited homology. Their sequence allowed Pik - p to be distinguished from Pik , Pik - s , Pik - m and Pik - h . Both Pikp - 1 and Pikp - 2 were constitutively expressed in cv. K60 and only marginally induced by blast infection.