Submitted to: Multicrop Aflatoxin and Fumonisin Elimination and Fungal Genomics Workshop-The Peanut Foundation
Publication Type: Proceedings
Publication Acceptance Date: 9/15/2006
Publication Date: 10/16/2006
Citation: Gao, X., Isakeit, T., Betran, J., Ni, X., Starr, J., Gobel, C., Brodhagen, M., Feussner, I., Keller, N., Engelberth, J., Tumlinson, J., Kolomiets, M. 2006. A Maize 9-Lipoxygenase is Required for Resistance to Aflatoxin Contamination, Insects, and Nematodes. In: Proceedings of the 6th Annual Fungal Genomics, the 7th Annual Multi-crop Fumonisin, and the 19th Annual Multi-crop Aflatoxin Elimination Workshops, October 16-18, 2006, Fort Worth, Texas. p. 54. Interpretive Summary: not required
Technical Abstract: Lipoxygenases (LOXs) are dioxygenases that catalyze the addition of molecular oxygen to polyunsaturated fatty acids including linoleic (LA) and linolenic acid (LeA), either at position 9 or 13 of their carbon chains, to produce a group of acyclic and cyclic hydropexides compounds called oxylipins. The resulting two distinct fatty acid hydroperoxides then enter separate biosynthetic pathways and lead to the accumulation of oxylipin compounds that have diverse physiological functions in plants. Previous reports showed that fungal oxylipins, so-called psi factor, play import roles in regulating both asexual and sexual spore development in A. nidulans. Also, it has been shown that a maize 9-LOX, ZmLOX3 (formerly cssap92) was induced by infection of kernels with A. flavus, and was accompanied by increased levels of 9S-HPODE. These data suggest an essential role for 9-LOXs signaling pathways in Aspergillus-host interaction. To provide genetic evidence of the role of this gene in resistance to aflatoxin contamination, we have generated Mu-insertional lox3 mutant and its near-isogenic lines (NILs) at BC4F5 stage. Here we present results of a two year/two location field study, which showed consistently that lox3-4 mutants accumulated significantly more aflatoxins compared to the wild-type NILs. Furthermore, kernel assays indicated that A. flavus produced significantly more conidia on lox3 mutants. lox3 mutants also displayed increased attractiveness to root-knot nematodes resulting in increased number of nematodes and eggs, suggesting that lox3 mutants are more susceptible to RKN. Moreover, under controlled green house infestation as well as under the conditions of natural infestation in field lox3 mutants are significantly more susceptible to insects. Collectively, our data suggest that ZmLOX3 is required for resistance of maize to aflatoxin contamination, as well as to insects and nematodes.