Function Of Immune-related QM Gene From Peneaus Japonicus

White spot syndrome virus (WSSV) is one of the most devastating pathogens. It has spread to shrimp-farming areas around the world with a high infection and mortality rate and caused tremendous economic loss. However, up to date, there is no efficient method to control the virus. In this study, RNAi in viral gene function was established in WSSV. Subsequently the role of QM in shrimp immunity was investigated. Our studies would be helpful for shrimp disease control.In this investigation, a specific 21 bp short interfering RNA (vp28-siRNA) of WSSV was used to induce gene silencing in Penaeus japonicus shrimp. It was found that the transcription and expression of vp28 gene were silenced by the sequence-specific siRNA. As revealed by quantitative PCR, the siRNA caused a significant reduction in viral DNA production of WSSV-infected shrimp. When treated with the siRNA, WSSV-infected shrimp had a reduced mortality rate. After three injections of siRNA, the virus was completely eradicated from WSSV-infected shrimp. These findings suggest that RNAi is capable of silencing sequence-specific genes of WSSV and might constitute a new therapeutic strategy for WSSV infection in shrimp.QM gene (designated as PjQM) was obtained from shrimp by RACE. It was found that the PjQM protein exhibited high homology with QMs from other species and contained functional motifs of QM. This gene was recombinantly expressed in E.coli and purified. The results of RT-PCR and Western blot indicated that the PjQM gene was ubiquitously expressed in shrimp tissues. Real-time PCR revealed that the PjQM was up-regulated after WSSV infection, suggesting that the PjQM protein might play a role in shrimp immune response against virus infection. As revealed by GST-pull down and mass spectrometry assays, the PjQM protein was interacted with shrimp hemocyanin and mysosin, which was further confirmed. The results of RNAi assays showed that the transcription and expression of PjQM was inhibited by sequence-specific siRNA. At this time, the PO activity was decreased in shrimp, suggesting that the QM was involved in shrimp immunity by regulating the PO activity through interaction with hemocyanin. This is the first report that the QM protein functions in immune response of animals.