Abstract
We have identified a lesion-mimic mutant, which contains an insertion of a rice retrotransposon Tos17 in OsPti1a gene. Accompanied by lesion formation, ospti1a mutant shows defense gene expression and enhanced resistance against compatible race of rice blast, Magnaporthe grisea. Reversely, overexpression of OsPti1a diminished resistance against incompatible race, suggesting that OsPti1a negatively regulates defense signaling in rice. To examine whether OsPti1a regulates R gene-mediated defense signaling, we focused on OsRAR1, which is genetically required for R gene function in several plant species. Repression of OsRAR1 suppressed cell death and defense gene expression in ospti1a mutant, indicating that OsPti1a may negatively regulate R gene-mediated disease resistance in rice through OsRAR1-dependent manner. Expression of tomato LePti1 can complement ospti1a mutant, whereas LePti1 enhances HR induction in tomato. Therefore, the downstream molecular switch controlling the HR was differently evolved between rice and tomato.
