The Key Role of Fatty Acid Synthase in Lipid Metabolism and Metamorphic Development in a Destructive Insect Pest, Spodoptera litura (Lepidoptera: Noctuidae)

Fatty acid synthase (FAS) is a key enzyme in the lipid synthesis pathway, however, its roles in insects remain largely unknown. Here, we firstly identified twoFASgenes from the transcriptome dataset of the general cutwormSpodoptera litura, which is a destructive insect pest of many crops. BothSlFAS1andSlFAS2were highly expressed in third instar larvae and in their fat bodies. Then, we successfully silencedSlFAS1in third instar larvae and the content of α-linolenic acid and triglyceride was significantly decreased. Besides that, the effect of FAS on the metamorphic development inS. liturawas evaluated. The results indicate that after silencingSlFAS1, the survival rates ofS. lituralarvae decreased significantly compared to the control groups. SilencingSlFAS1in fifth instar larvae resulted in more malformed pupae and adults, and the emergence rates were significantly reduced. Furthermore, the ecdysone content in the haemolymph of fifth instar larvae was significantly decreased after silencingSlFAS1. In addition, knocking downSlFAS1significantly alters the expression of other key genes in the lipogenesis pathway, implying that FAS has an impact on the lipogenesis pathway. The present study deepens the understanding of FAS in insects and provides novel potential targets for managing insect pests.Keywords:fatty acid synthase (FAS);Spodoptera litura;lipid metabolism;metamorphosis;RNA interference