Resistance to Magnaporthe grisea in transgenic rice with suppressed expression of genes encoding allene oxide cyclase and phytodienoic acid reductase.

Linolenic acid (18:3) and its derivative jasmonic acid (JA) are important molecules in disease resistance in many dicotyledonous plants. We have previously used 18:3- and JA-deficient rice (F78Ri) to investigate the roles of fatty acids and their derivatives in resistance to the blast fungus Magnaporthe grisea [A. Yara, T. Yaeno, J.-L. Montillet, M. Hasegawa, S. Seo, K. Kusumi, K. Iba, Enhancement of disease resistance to Magnaporthe grisea in rice by accumulation of hydroxy linoleic acid, Biochem. Biophys. Res. Commun. 370 (2008) 344-347; A. Yara, T. Yaeno, M. Hasegawa, H. Seto, J.-L. Montillet, K. Kusumi, S. Seo, K. Iba, Disease resistance against Magnaporthe grisea is enhanced in transgenic rice with suppression of omega-3 fatty acid desaturases, Plant Cell Physiol. 48 (2007) 1263-1274]. However, because F78Ri plants are suppressed in the first step of the JA biosynthetic pathway, we could not confirm the specific contribution of JA to disease resistance. In this paper, we generated two JA-deficient rice lines (AOCRi and OPRRi) with suppressed expression of the genes encoding allene oxide cyclase (AOC) and 12-oxo-phytodienoic acid reductase (OPR), which catalyze late steps in the JA biosynthetic pathway. The levels of disease resistance in the AOCRi and OPRRi lines were equal to that in wild-type plants. Our data suggest that resistance to M. grisea is not dependent on JA synthesis.