Submitted to: Molecular Plant-Microbe Interactions
Publication Type: Peer reviewed journal
Publication Acceptance Date: 3/28/2007
Publication Date: 7/23/2007
Citation: Gao, X., Shim, W., Gobel, C., Kunze, S., Feussner, I., Meeley, R., Balint Kurti, P.J., Kolomiets, M. 2007. Disruption of a maize 9-lipoxygenase results in increased resistance to fungal pathogens and reduced levels of contamination with mycotoxin fumonisin. Molecular Plant-Microbe Interactions. 20:922-933. Interpretive Summary: A gene called ZmLOX3 is involved in the modification of fatty acids in maize cells. Disease assays show that a plant with this gene inactivated is more resistant to a variety of fungal pathogens. These pathogens cause fewer symptoms, produce less toxin and produce fewer spores. We hypothesize that the function of this gene is required for fungal pathogenesis in plants.
Technical Abstract: Plant oxylipins, produced via the lipoxygenase (LOX) pathway, function as signals in defense and development. In fungi, oxylipins are potent regulators of mycotoxin biosynthesis and sporogenesis. Previous studies showed that plant 9-LOX-derived fatty acid hydroperoxides induce conidiation and mycotoxin production. Here, we tested the hypothesis that oxylipins produced by the maize 9-LOX pathway are required by pathogens to produce spores and mycotoxins and to successfully colonize the host. Maize mutants were generated in which the function of a 9-LOX gene, ZmLOX3, was abolished by an insertion of a Mutator transposon in its coding sequence, which resulted in reduced levels of several 9-LOX derived hydroperoxides. Supporting our hypothesis, conidiation and production of the mycotoxin fumonisin B1 by Fusarium verticillioides were drastically reduced in kernels of the lox3 mutants as compared to near-isogenic wild types. Similarly, conidia production and disease severity of anthracnose leaf blight caused by Colletotrichum graminicola were significantly reduced in the lox3 mutants. Moreover, lox3 mutant displayed increased resistance to southern leaf blight caused by Cochliobolus heterostrophus and stalk rots caused by both F. verticillioides and C. graminicola. These data strongly suggest that oxylipin metabolism mediated by a specific plant 9-LOX isoform is required for fungal pathogenesis including disease development and production of spores and mycotoxins.