Mycotoxin contamination in maize is controlled by oxylipin signals

Mycotoxins are the most potent natural toxins and carcinogens that adversely affect diverse farm animals, poultry and humans. In corn, the major mycotoxin producing fungi are Aspergillus flavus and Fusarium verticillioides. Plant and fungal oxylipins are oxygenated fatty acids produced by diverse oxygenases including lipoxygenases (LOX). Plant oxylipins such as jasmonic acid (JA) function as signals in regulating defense. In fungi, oxylipins are potent regulators of mycotoxin biosynthesis and sporogenesis. Evidence will be presented showing that in addition to the major role of JA in defense against F. verticillioides, a range of understudied plant oxylipins may facilitate the pathogenic process while other oxylipins act to induce defense by upregulating JA biosynthesis. Supporting the hypothesis that oxylipins of both plant and fungal origin are engaged in the signaling cross-talk, analyses of F. verticillioides oxylipin mutants uncovered their dual role in both promoting pathogenesis and acting as elicitors of plant defense response. Overall, the study has identified several LOX genes required for resistance to F. verticillioides as well as a gene mediating susceptibility to fungal colonization and stimulating toxin production.