Abstract
We have investigated the function of a rice protein kinase OsPti1a, a homologue of tomato Pti1 isolated as an interactor of the R gene Pto. The OsPti1a functions as a negative regulator of resistance to blast fungus in rice, whereas the Pti1 plays as a positive regulator of bacterial resistance in Solanaceae. Introduction of the Pti1 complements the ospti1a mutant phenotype, suggesting that both proteins similarly act as kinases in signal transduction pathways in defence mechanism, diverged between dicot and monocot. To elucidate the molecular mechanism involving OsPti1a, yeast two hybrid screening was carried out to specify unknown players implicated in defence in rice. Two OsPti1a-interacting partners were isolated; one is a protein kinase showing similarity to the tomato Adi3 and the other is a carboxylesterase similar to the tobacco HSR203J. Their involvement upon the defence and the mechanism of signal transduction via phosphorylation will be discussed.
