Rapid and mass rearing of Locusta migratoria manilensis is an urgent need to meet the increasing demand for food of people. In this study, the effects of four artificial feeds on the development, reproduction and the activities of detoxification and protective enzymes of L. migratoria manilensis in three successive generations were investigated. The results showed that sucrose and monosodium glutamate (MSG) significantly increased the net reproductive rate (R0) and the intrinsic growth rate (rm) of L. migratoria manilensis, but sodium chloride (0.17%) suppressed this increase. Furthermore, the artificial feed with sucrose and monosodium glutamate increased the activities of esterase (EST), acetylcholinesterase (AChE), glutathione-Stransferase (GST), multi-function oxidase (MFO), phenol oxidase (PO), catalase (CAT) and peroxidase (POD), but inhibited the activity of superoxide dismutase (SOD). However, sodium chloride (0.17%) increased the activities of EST, AChE, CAT and SOD, and inhibited the activities of MFO, GST, PO and POD. Correlation analysis found that the increasing of PO activity and the decreasing of SOD activities were significantly related with the increasing of the intrinsic growth rate (rm). The above results indicated that sucrose and monosodium glutamate could promote the development and reproduction of L. migratoria manilensis, but Na+ inhibit such promotion with the concentration above 0.2%. The activities of PO and SOD can be used as biochemical standard to assess the effect of artificial feed.

A cDNA encoding a sigma-class glutathione S-transferase of the locust, Locusta migratoria manilensis (LmGSTs1), was cloned by reverse transcriptase-polymerase chain reaction. The 830 bp-long cDNA encoded a 615 bp open reading frame (204 amino acid polypeptide), which exhibited the structural motif and domain organization characteristic of GST sigmaclass. It revealed 59, 57, 57, and 56% identities to sigma-class GSTs from Blattella germanica, Gryllotalpa orientalis, Nasonia vitripennis, and Pediculus humanus corporis, respectively. A recombinant protein (LmGSTs1) was functionally expressed in Escherichia coli cells in a soluble form and purified to homogeneity. LmGSTs1 was able to catalyze the biotranslation of glutathione with 1-chloro-2,4-dinitrobenzene, a model substrate for GSTs, as well as with p-nitro-benzyl chloride. Its optimal activity was observed at pH 8.0 and at 30°C. Incubation for 30 min at temperatures below 50°C scarcely affected the activity. The I50 of reactive blue (RB) was 18.5 μmol L-1. In the presence of 0.05 mmol L-1 ethacrynic acid (ECA), LmGSTs1 showed (81±3)% of the original activities.