Location: Corn Host Plant Resistance ResearchTitle: Genetic characterization of the maize lipoxygenase gene family in relation to aflatoxin accumuation resistance.
|OGUNOLA, OLUWASEUN - Mississippi State University|
|KOLOMIETS, MIKE - Texas A&M University|
|BORREGO, ELI - Texas A&M University|
|TANG, JULIET - Us Forest Service (FS)|
|Williams, William - Paul|
Submitted to: PLoS Genetics
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/5/2017
Publication Date: 7/17/2017
Citation: Ogunola, O., Hawkins, L.K., Mylroie, J.E., Kolomiets, M., Borrego, E., Tang, J., Williams, W.P., Warburton, M.L. 2017. Genetic characterization of the maize lipoxygenase gene family in relation to aflatoxin accumuation resistance. PLoS ONE 12(7):e0181265.
Interpretive Summary: Aspergillus flavus is a fungal pathogen of maize that creates a compound toxic to humans and animals, and it is therefore of great interest to find or breed maize cultivars that can resist infection and growth of this fungus. The creation of resistant maize cultivars would be more efficient if we knew which of the maize genes were causing the resistance, and how they were doing so. The genes that encode the enzyme lipoxygenase have been known for some time to cause increased resistance to some plant pathogens, including several fungi. There are 13 lypogygenase genes in maize, and we wanted to know if any (or all) of them contribute to resistance against A. flavus. Thus, we characterized each gene in this gene family, and measured the effect of each one on resistance to maize in our gene mapping maize populations. Several had a small but measurable effect on resistance, and the effect and statistical significance of one of these genes is large enough to warrant further investigation. In general, however, increases in resistance attributable to the lypoxygenase genes are not large and may not contribute to efficient improvement.
Technical Abstract: Maize (Zea mays L.) is a globally important staple food crop. It is prone to contamination by aflatoxin, a secondary carcinogenic metabolite produced by the fungus Aspergillus flavus. An efficient approach to combat the accumulation of aflatoxin is the development of germplasm resistant to infection and spread of A. flavus. Lipoxygenases (LOXs) are a group of non-heme iron containing dioxygenase enzymes that catalyze oxygenation of polyunsaturated fatty acids (PUFAs), and LOX derived oxilipins play critical roles in plant defense against pathogens including A. flavus. The objectives of this study were to summarize sequence diversity and expression patterns for all LOX genes in the maize genome, and to map their effect on aflatoxin accumulation via linkage and association mapping. In total, 13 LOX genes were identified, characterized, and mapped. The sequence of one gene, ZmLOX 10, is reported in its entirety from 8 inbred lines. Genes ZmLOX 1/2, 5, 8, 9, 10 and 12 (GRMZM2G156861, GRMZM2G102760, GRMZM2G104843, GRMZM2G017616, GRMZM2G015419, and GRMZM2G106748, respectively) fell under previously published QTL in one or more mapping populations and are linked to a measurable effect on the reduction of aflatoxin in maize grains. Association mapping results found 28 of the total 726 SNPs tested were associated with reduced aflatoxin levels at p = 9.71 x 10-4 according to the association statistics. These fell within or near nine of the ZmLOX genes. This work confirms the importance of some lipoxygenases for fungal resistance, and may be used to direct future selection for resistance in maize.