Feeding dsSerpin1 Enhanced Metarhizium anisopliae Insecticidal Efficiency against Locusta migratoria manilensis

Abstract

RNA interference (RNAi) induces gene silencing in order to participate in immune-related pathways. Previous studies have shown that the LmSerpin1 gene upregulates the immune responses of Locusta migratoria manilensis, and that the infection of locusts with Metarhizium anisopliae can be enhanced through the injection of the interfering dsSerpin1. In this study, dsRNA was synthesized from the Serpin1 gene and fed to the third instars of L. m. manilensis at concentrations of 5 μg, 10 μg, and 20 μg. Feeding dsSerpin1 increased the mortality of L. m. manilensis, and 20 μg dsSerpin1 had the highest lethality, followed by 10 μg dsSerpin1, with the lowest being observed at 5 μg dsSerpin1. Serpin1 silencing and temperature fever induction by feeding with dsSerpin1 had a strong synergistic effect on M. anisopliae, showing a dose-dependent response. When L. m. manilensis were fed on a diet containing 20 μg dsRNA and M. anisopliae (2.5 × 108 spores/g wheat bran), 3-day mortalities significantly increased. The dsSerpin1 plus M. anisopliae treatments resulted in a 6-day mortality of 60%, accelerating insect death. These results indicated that feeding with dsSerpin1 could be an effective way to control pests and that the control effect and dsRNA concentration were dose-dependent within the first seven days. In particular, 20 μg was an effective dosage to enhance the insecticidal efficiency of M. anisopliae.