Rice blast resistance gene Pii is controlled by a pair of NBS-LRR genes Pii-1 and Pii-2

Abstract

Nucleotide-binding, leucine-rich repeat receptors (NLRs) are conserved cytosolic receptors that recognize pathogen effectors and trigger immunity in plants. Recent studies indicate that NLRs function in pairs. Rice resistance gene Pii has been known to confer resistance against rice blast pathogen Magnaporthe oryzae carrying AVR-Pii. Previously we reported isolation of Pii gene from the rice cultivar Hitomebore (Takagi et al. 2013). To further understand rice components required for Pii-mediated resistance, we screened 5,600 mutant lines of Hitomebore cultivar and identified two mutants that lost Pii resistance without any changes in Pii gene sequence. Application of MutMap-Gap, the whole genome sequencing-based method of mutation identification, to the two mutants revealed that they have mutations in another NLR gene located close to Pii. The F1 plants derived from a cross of the two mutants showed pii phenotype, demonstrating that the newly identified NLR gene is indeed a component of Pii resistance. We thus designate the previously isolated Pii gene as Pii-1 and the newly isolated NLR gene as Pii-2.