Inhibitory effect of genistein and PTP1B on grasshopper Oedaleus asiaticus development

Abstract

Protein tyrosine kinase (PTKs) and protein tyrosine phosphatase (PTPs) collectively regulate the insect insulin-signaling pathway (ISP), cell growth, metabolism, proliferation, differentiation, cell communication and monitoring of immune responses. We studied the inhibitory response of the grasshopper Oedaleus asiaticus Bey-Bienko to treat with the flavonoid genistein (PTK inhibitor), the enzyme PTP1B-IN-1 (PTP1B inhibitor) and control (dimethyl sulfoxide (DMSO)). Mean survival rates were not significantly different amongst the three treatments, but growth rate, body mass, and overall biological performance were reduced significantly following treatment with genistein. On comparison, treatment with PTP1B-IN-1 was not significantly different from the control. Relative gene expression of INSR, IRS, PI3K, PDK, and Akt was substantially lower (P < 0.05) following treatment with genistein compared to PTP1B-IN-1 and control. Similarly, gene expression and protein phosphorylation levels of the PTK5, PTP1B → FOXO cascade, indicators of stress response in the ISP, were also reduced in response to genistein treatments. The activity of the protective enzymes (POD and CAT) was upregulated by FOXO in response to PTP1B-IN-1. Our results demonstrated that genistein negatively regulates the ISP pathway, with a consequent effect on growth and development of O. asiaticus, as higher energy was required for detoxification. Given the negative effect of genistein on O. asiaticus physiology and development, the compound could be used in a biopesticide formulation for insect pest control in grasslands and other crop plants as a potential application to grasshopper biological control.