Fatty Acid Desaturases in the Chloroplast and Endoplasmic Reticulum Promote Susceptibility to the Green Peach Aphid in .

Fatty acid desaturases (FADs) in plants influence levels of susceptibility to multiple stresses, including insect infestations. In this study, populations of the green peach aphid () on were reduced by mutations in three desaturases: , which encodes a chloroplastic stearoyl-[acyl-carrier-protein] 9-desaturase, and or which encode ω-3 FADs in the chloroplast and endoplasmic reticulum (ER), respectively. These data indicate that certain FADs promote susceptibility to aphids and that aphids are impacted by desaturases in both the chloroplast and ER. Aphid resistance in , , and , singly or in combination, might involve altered signaling between these subcellular compartments. C18:1 levels are depleted in , whereas C18:2 accumulation is enhanced in and . In contrast, has higher than normal C18:2 levels but also high C18:1 and low C18:0 and does not impact aphid numbers. Potentially, aphids may be influenced by the balance of multiple fatty acids (FAs) rather than by a single species, with C18:2 promoting aphid resistance and C18:1 promoting susceptibility. Although the mutant also accumulates higher-than-normal levels of C16:2, this FA does not contribute to aphid resistance because a triple mutant line that lacks detectable levels of C16:2 () retains comparable levels of aphid resistance as In addition, aphid numbers are unaffected by the mutation that inhibits C16:1 synthesis. Together, these results demonstrate that certain FADs are important susceptibility factors in plant-aphid interactions and that aphid resistance is more strongly associated with differences in C18 abundance than C16 abundance.[Formula: see text] Copyright © 2021 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license.