The phloem-feeding aphids feed on a variety of plants and limit plant productivity/quality. Efforts to enhance aphid resistance in plants have been hampered by the lack of understanding of resistance mechanisms to aphids. We have established a model system consisting of the plant, Arabidopsis thaliana and the phloem feeder, Green peach aphid (GPA; Myzus persicae) to study plant responses to aphid feeding. This system offers the combined power of genetics, molecular biology and metabolomics to enhance our understanding of plant response to aphids. Initial investigations suggested that the loss of salicylic acid (SA), jasmonic acid (JA) and ethylene signaling do not significantly alter Arabidopsis resistance to GPA. The Arabidopsis pad4 (phytoalexin-deficient) and ssi2 (suppressor of SA-insensitivity) mutant plants exhibit altered resistance to GPA; resistance to GPA was compromised in the pad4 and enhanced in the ssi2 mutant plants. In comparison, an intermediate level of resistance was observed in the ssi2 pad4 double mutant. PAD4 encodes a putative lipase and SSI2 encodes a stearoyl-ACP desaturase, suggesting the involvement of lipids/lipid dynamics in plant defense to GPA. In agreement with a role for lipids/lipid dynamics in resistance to GPA, the sfd1 (suppressor of fatty acid desaturase deficiency) mutant, which alters plastid lipid biosynthesis, compromises the ssi2-conferred enhanced resistance to GPA.Electron-ionization tandem mass spectroscopy has been used to profile changes in plant lipid composition in response to aphid feeding. Microarray analysis identified several GPA-responsive genes and has enabled us to identify novel biochemical pathways that may be involved in plant defenses to aphids.
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