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Aspergillus Infection Inhibits the Expression of Peanut 13S-HPODE-Forming Seed Lipoxygenases

¹Department of Plant Pathology, University of Wisconsin-Madison, Madison 53706, U.S.A.; ²Georg-August-University Göttingen, Albrecht-von-Haller Institute for Plant Sciences, Department for Plant Biochemistry, Justus-von-Liebig-Weg 11, D-37077 Göttingen, Germany; ³United States Department of Agriculture-Agricultural Research Service Vegetable Crops Research Unit, University of Wisconsin-Madison, Madison 53706, U.S.A.

Oxylipins recently have been implicated as signaling molecules for cross-kingdom communication in plant-pathogen interactions. Linoleic acid and its two plant lipoxygenase (LOX) 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 sporulation, 9S-HPODE stimulates and 13S-HPODE inhibits mycotoxin production. Additionally, Aspergillus flavus infection of seed promotes linoleate 9-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. PnLOX2 and PnLOX3 both are 13S-HPODE producers (linoleate 13-LOX) and, in contrast to previously characterized 9-LOX or mixed function LOX genes, are repressed between 5-fold and 250-fold over the course of A. flavus infection. The results of these studies suggest that 9SHPODE and 13S-HPODE molecules act as putative susceptibility and resistance factors respectively, in Aspergillus seed-aflatoxin interactions.

Additional keywords: Arachis hypogaea, defense.