Fatty acid changes in soybean (Glycine max) under soybean aphid (Aphis glycines) infestation and their implications on plant defense against insects

Abstract

The soybean aphid (Aphis glycines) is one of the most important pests of soybeans in the Northcentral region of the US. It has been hypothesized that aphids avoid effective defenses by inhibiting induction of jasmonate-regulated plant defense responses. Given the role fatty acids play in jasmonate-induced plant defenses, we analyzed the fatty acid profile of soybean leaves and seeds from aphid-infested plants. Results showed that aphids reduce the amount of polyunsaturated fatty acids in leaves with a concomitant increase in palmitic acid. In seeds, a reduction in polyunsaturated fatty acids was associated with an increase in stearic acid and oleic acid. One of the polyunsaturated fatty acids, linolenic acid, is the precursor of jasmonate; thus, these changes in fatty acid metabolism may be examples of “metabolic hijacking” where one organism takes over the metabolism of another, leading to prevention of production of compounds that would otherwise be detrimental to the attacker. The pattern of fatty acid changes points to a possible interference in fatty acid biosynthesis and desaturation, especially at FAB1, leading to an increase in palmitate, and at FAD2 and FAD6, leading to a reduction in polyunsaturated fatty acids. However, the regulation does not seem to be transcriptional.