Identification of Fatty Acid Synthase in Arma chinensis and Its Expression Profiles in Response to Starvation

Fatty acids are the main form of energy production and storage in insects, and fatty acid synthase (FAS) plays a major role in this process. Arma chinensis is a natural enemy used in China to control agricultural pests. While its whole genome has been assembled, its FAS genes remain undescribed. Herein, we aim to identify the FAS genes of A. chinensis and explore their expression during starvation. Phylogenetic analysis identified nine FAS genes (ArmaFas1-ArmaFas9). During the predatory developmental stages, ArmaFas9 expression gradually increased from the 2nd to the 4th instar, peaking at the 5th instar and plateauing at the adult stage. Female adults exhibited the highest expression of ArmaFas9 in their fat body and the lowest expression in their salivary glands, whereas male adults demonstrated the opposite pattern. ArmaFas9 expression was negatively correlated with starvation duration. Compared to the controls, starved adult females exhibited a downward expression trend, whereas starved adult males demonstrated an initial increase, followed by a downward trend after 7 days. Starvation and refeeding increased ArmaFas9 expression. These results demonstrate the important role of ArmaFas9 in A. chinensis growth and development, providing a basis for further studies on lipid synthesis in predatory bugs.