Roy J. Carver Department of Biochemistry, Biophysics & Molecular Biology

"Soybean lipidome response to soybean aphid infestation"

Aphids are specialized insects that feed on phloem sap.  They alter plant metabolism, affect plant growth and development, and are also vectors for plant viruses. Their feeding habits result in little mechanical damage and aphids avoid triggering many plant defenses commonly elicited by other herbivores.  It has been proposed that aphids can suppress effective defenses through the induction of decoy responses.  Several lines of evidence suggest that lipid-derived signals and phytoalexins have an effective role as defenses against these insects. Previously, we showed that soybean aphids, Aphis glycines Matsumura, affect fatty acid accumulation in soybean plants. 

Here, we performed lipidomics and transcriptome analyses of soybean leaves that were infested with soybean aphids for 7 days to identify further changes in lipid composition triggered by aphid feeding.  We found significant changes in membrane lipid species including digalactosyldiacylglycerol (DGDG), monogalactosyldiacylglycerol (MGDG), phosphatidylglycerol (PG), lysophosphatidylethanolamine (lysoPE), phosphatidylcholine (PC), phosphatidylethanolamine (PE), phosphatidylinositol (PI), and phosphatidic acid (PA). Transcriptome data identified a large number of differentially expressed genes associated with lipid metabolism, including changes in different fatty acid desaturases, and a strong induction of phospholipase A, phospholipase C, and phospholipase D.

We also observed a strong induction of the oxylipins biosynthesis pathway, and negative regulation of sphingolipids biosynthesis. The production and transport of cuticular waxes, including the synthesis of long-chain fatty acids is strongly repressed after aphid feeding. Our results suggest that membrane phospholipids play an important role in the soybean response to aphid feeding, and that fatty acid-, PA-, and PI-derived signals likely mediate this interaction.