Submitted to: Molecular Plant Microbe Interactions
Publication Type: Peer reviewed journal
Publication Acceptance Date: 6/4/2005
Publication Date: 10/1/2005
Citation: Tsitsigiannis, D.I., Kunze, S., Willis, D.K., Feussner, I., Keller, N.P. 2005. Aspergillus infection inhibits the expression of peanut 13s-hpode seed lipoxygenases. Molecular Plant Microbe Interactions. 18:1081-1089. Interpretive Summary: Fungi in the species Aspergillus are important pathogens of many crop species. These fungi often infect grain or legumes such as peanuts prior to harvest and the fungus contaminates the crop with aflatoxins. The contamination of the food source with this potent toxin makes the food source hazardous to consume by humans and animals. In this paper, we describe the effect of Aspergillus infection on peanut. We have discovered that this infection inhibits the expression of an enzyme in the peanut that usually produces a compound that inhibits the production of toxin. In this way, we have established that the fungus actively alters the metabolism of the plant host to favor the production of toxin and increase it’s ability to infect the plant. "This work reveals a new biological target for the chemical or biological reduction of aflatoxin contamination in agronomically important crops such as peanuts and feed grains."
Technical Abstract: Oxylipns have recently been implicated as signaling molecules for cross kingdom communication in plant/pathogen interactions. Linoleic acid and its two plant lipoxygenase oxylipin products 9- and 13 hydroperoxy fatty acids (9S- and 13S-HPODE) have been shown to have a significant effect on differentiation processes in the mycotoxigenic seed pathogens Aspergillus spp. Whereas both fatty acids promote asexual sporulation, 9S-HPODE stimulates and 13S-HPODE inhibits mycotoxin production. Additionally, Aspergillus infections of seed promotes 9S-HPODE LOX expression and 9S-HPODE accumulation. Here, we describe the characterization of two peanut seed lipoxygenase alleles (pnlox2 and pnlox3) highly expressed in mature seed. Pnlox-2 and Pnlox-3 are both 13S-HPODE producers and, in contrast to 9-LOX genes, are repressed between 5-fold and 250-fold over the course of Aspergillus infection. These studies suggest that 9S HPODE and 13S-HPODE molecules act as putative susceptibility and resistance factors respectively in Aspergillus/seed/aflatoxin interactions.