Oryza sativa proteinase inhibitor gene, OsPIN, whose mRNA specifically accumulates in a compatible host–blast pathogen interaction

A rice proteinase inhibitor (PIN), Oryza sativa proteinase inhibitor (OsPIN), cDNA clone, was identified from a differentially expressed cDNA library of the rice leaves (cv. Nipponbare) infected with the blast pathogen, Magnaporthe grisea. OsPIN, which showed considerable similarity at amino acid level to the available potato, Arabidopsis and turnip PINs in the database, but very low similarity to the well-characterized potato and tomato PIN I and PIN IIs, exists as a single copy in the rice genome. The OsPIN transcript specifically accumulated in abundance with time in a compatible, but not incompatible, host–pathogen interaction. Furthermore its transcript, occasionally detected in the healthy leaves, did not increase after cut. Interestingly, among the global signals known to modulate defense/stress pathways, jasmonic acid, salicylic acid and hydrogen peroxide up-regulated the OsPIN transcript, under both light and dark. In the light of the specific nature of OsPIN towards host–pathogen interaction and signaling molecules, and the importance of PINs in plants, it is thought that its identification and basic study on expression/regulation are an important step in our ultimate goal to improve rice and other major cereal crops against the changing environment.