Soybean Aphid Infestation Induces Changes in Fatty Acid Metabolism in Soybean

Abstract

The soybean aphid (Aphis glycines Matsumura) is one of the most important insect pests of soybeans in the North-central region of the US. It has been hypothesized that aphids avoid effective defenses by inhibition of jasmonate-regulated plant 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. Aphid infestation reduced levels 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. Soybean plants challenged with the brown stem rot fungus or with soybean cyst nematodes did not present changes in fatty acid levels in leaves or seeds, indicating that the changes induced by aphids are not a general response to pests. 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” by the aphid to avoid the induction of effective defenses. Based on the changes in fatty acid levels observed in seeds and leaves, we hypothesize that aphids potentially induce interference in the fatty acid desaturation pathway, likely reducing FAD2 and FAD6 activity that leads to a reduction in polyunsaturated fatty acids. Our data support the idea that aphids block jasmonate-dependent defenses by reduction of the hormone precursor.

Modulation of Legume Defense Signaling Pathways by Native and Non-native Pea Aphid Clones

“…The fatty acid substrate of the JA pathway is α-linolenic acid (18:3), which is produced from galactolipids of chloroplast membranes (Wasternack and Hause, 2013). Recently Kanobe et al (2015) detected less α-linolenic acid in soybean plants ( G. max ) infested with the soybean aphid ( Aphis glycine ) than in uninfested control plants or plants infested with other soybean antagonists, the soybean cyst nematode ( Heterodera glycines ) and the brown stem rot ( Cadophora gregata ). This suggests that certain pea aphid clones might suppress one of the steps in JA signaling or biosynthesis prior to the formation of α-linolenic acid.…”

Magnaporthe oryzae Systemic Defense Trigger 1 (MoSDT1)-Mediated Metabolites Regulate Defense Response in Rice

“…oryzae-infected MoSDT1-transgenic rice Linolenic acid and linoleic acid are precursors of jasmonic acid synthesis [10]. In this study, these two metabolites and salicylic acid were identified to accumulate in M. oryzae-infected MoSDT1-transgenic rice at 72 h. Meanwhile, the contents of JA, JA-Ile, and salicylic acid were higher in infected transgenic rice than infected wild-type rice.…”

“…Linolenic acid and linoleic acid among lipids and lipid-like molecules, raffinose among organic oxygen compounds, tyramine among benzenoids, and unclassified alphapinene showed significant accumulation at 72 h. Oxalate among organic acids and derivatives decreased at 72 h and became undetectable at the other two time points. Anthranilic acid and dopamine in benzenoids were accumulated significantly at 0 h and 120 h. Organic oxygen compounds [9], lipids and lipid-like molecules [10], benzenoids [11,12], and many unclassified metabolites were detected in M. oryzae-infected MoSDT1-transgenic resistant rice. These are the core defense metabolites in M. oryzae-infected MoSDT1-transgenic plants.…”

“…When pathogenic fungi infect plants, sugar levels in plant tissues elevate to activate plant defense responses, which participate in regulating hormonal signaling network of plant immune system and induce plants to present stronger resistance to pathogens [8]. Diverse organic oxygen compounds [9], lipids [10], benzenoids [11], and organic acids [12] play an important role in plant defense responses. Critical metabolic pathways, such as carbohydrate metabolism, amino acid metabolism, galactose metabolism, glyoxylate, and dicarboxylate metabolism, starch and sucrose metabolism, ABC transporters, etc., are activated when plants are infected by pathogens [8].…”

Pest management of soybean aphid and soybean cyst nematode: Host-plant resistance, entomopathogens, and seed-applied pesticides

“…This process of hijacking plant defenses has also been observed in insect herbivores, including aphids (Hillwig et al 2016). Soybean aphid feeding can alter fatty acid metabolism and thereby affect the precursors to jasmonate-dependent defenses (Kanobe et al 2015). Another study showed some evidence that A. glycines can obviate plant defenses conferred by the Rag1 gene.…”