The Gain-of-Function Mutation, OsSpl26, Positively Regulates Plant Immunity in Rice

Rice spotted-leaf mutants are ideal materials to study the molecular mechanism underlying programmed cell death and disease resistance in plants. has previously been identified as the candidate gene responsible for the spotted-leaf phenotype in rice ( mutant. Here, we cloned and validated that is the locus controlling the spotted-leaf phenotype of by reverse functional complementation and CRISPR/Cas9-mediated knockout of the mutant allele. The recessive wild-type allele ( , ) is highly conservative in grass species and encodes a putative G-type lectin S-receptor-like serine/threonine protein kinase with 444 amino acid residuals. OsSPL26 localizes to the plasma membrane and can be detected constitutively in roots, stems, leaves, sheaths and panicles. The single base substitution from T to A at position 293 leads to phenylalanine/tyrosine replacement at position 98 in the encoded protein in the mutant and induces excessive accumulation of H O , leading to oxidative damage to cells, and finally, formation of the spotted-leaf phenotype in . The formation of lesions not only affects the growth and development of the plants but also activates the defense response and enhances the resistance to the bacterial blight pathogen, pv. . Our results indicate that the gain-of-function by the mutant allele positively regulates cell death and immunity in rice.