Role of PTP/PTK trans activated insulin-like signalling pathway in regulation of grasshopper ( Oedaleus asiaticus ) development

Abstract

Protein tyrosine phosphatase (PTPs) and protein tyrosine kinase (PTKs) genes are responsible for the regulation of insect insulin-like pathway (ILP), cells growth, metabolism initiation, gene transcription and observing immune response. Signal transduction in insect cell is also associated with PTPs and PTKs. The grasshopper (Oedaleus asiaticus) 'Bey-Bienko' were treated with dsRNA of protein tyrosine non-receptor type 4 (PTPN4) and protein tyrosine kinase 5 (PTK5) along with control (water). Applying dsPTK5 treatments in 5th instar of Oedaleus asiaticus, significant reduction was recorded in body dry mass, growth rate and overall performance except survival rate. Whereas with PTPN4, no such significant impact on all of these growth parameters was recorded. Expression of genes in ILP 5th instar of Oedaleus asiaticus by the application of dsPTPN4 and dsPTK5 revealed that PTK, INSR (insulin receptor), IRS (insulin receptor substrate), PI3K (phosphoinositide 3-kinase), PDK (3-phosphoinositide-dependent protein kinase), Akt (protein kinase B) and FOXO (forkhead transcription factor) significantly expressed with downregulation except PTPN4, which remained non-significant. On the other hand, the phosphorylation level of ILP four proteins in O. asiaticus with the treatment of dsPTPN4 and dsPTK5 significantly affected P-IRS and P-FOXO, while P-INSR and P-AKT remained stable at the probability level of 5%. This indicated that the stress response in the O. asiaticus insulin-like signalling pathway (ILP) reduced. Regarding association of protective enzymatic activities, ROS (relative oxygen species), CAT (catalase) and PO (phenol oxidase) increased significantly with exposure to dsPTK5 as compared to dsPTPN4 and control, while exposure of 5th instar of O. asiaticus to dsPTPN4 treatment slightly raised CAT and PO activities with but significant contribution. No such significant effect on MFO and POD was seen using dsPTPN4 and dsPTK5. This showed that in the ILP of O. asiaticus, PTK5 was detrimental to growth, body mass and overall performance, which ultimately benefited insect detoxification with high-energy cost.

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