Abstract
Linoleic acid (18:2) and linolenic acid (18:3) are the sources for various oxidized metabolites, oxylipins, which are crucial for the induction of pathogen defense responses in plants. We show that 18:2-derived oxylipins play an important role in resistance to a phytopathogenic fungus, Magnaporthe grisea, in rice. We generated 18:2-accumulating transgenic rice plants (F78Ri) using RNA-interference of two ω-3 fatty acid desaturases, OsFAD7 and OsFAD8, which desaturate 18:2 to 18:3. The F78Ri plants exhibited enhanced resistance to M. grisea in a non-race-specific manner. 18:2-derived hydroperoxides and hydroxides (HPODEs and HODEs, respectively) inhibited in vitro growth of M. grisea more strongly than their respective 18:3-derived counterparts. In F78Ri plants, the endogenous levels of HPODEs and HODEs increased significantly, compared with wild-type plants. These results indicate that, in F78Ri plants, the increased accumulation of HPODEs and HODEs results in elevated antifungal activity against M. grisea, and therefore enhanced disease resistance.
