PmKuSPI is regulated by pmo-miR-bantam and contributes to hemocyte homeostasis and viral propagation in shrimp

The Kunitz-type serine protease inhibitor (KuSPI) is a low molecular weight protein that plays a role in modu-lating a range of biological processes. In Penaeus monodon, the PmKuSPI gene has been found to be highly expressed in the white spot syndrome virus (WSSV)-infected shrimp and is predicted to be regulated by a conserved microRNA, pmo-miR-bantam. We reported that, despite being upregulated at the transcriptional level, the PmKuSPI protein was also upregulated after WSSV infection. Silencing the PmKuSPI gene in healthy shrimp had no effect on phenoloxidase activity or apoptosis but resulted in a delay in the mortality of WSSV-infected shrimp as well as a reduction in the total hemocyte number and WSSV copies. According to an in vitro lucif-erase reporter assay, the pmo-miR-bantam bound to the 3 ' UTR of the PmKuSPI gene as predicted. In accordance with the loss of function studies using dsRNA-mediated RNA interference, the administration of the pmo-miR-bantam mimic into WSSV-infected shrimp lowered the expression of the PmKuSPI transcript and the PmKuSPI protein, as well as the WSSV copy number. According to these results, the protease inhibitor PmKuSPI is post-transcriptionally controlled by pmo-miR-bantam and plays a role in hemocyte homeostasis, which in turn affects shrimp susceptibility to WSSV infection.

Automated summary

The low molecular weight protein KuSPI plays a role in modulating various biological processes. In Penaeus monodon, the PmKuSPI gene is highly expressed in WSSV-infected shrimp and is regulated by a conserved microRNA, pmo-miR-bantam. Silencing the PmKuSPI gene in healthy shrimp resulted in delayed mortality and reduced hemocyte number and WSSV copies in infected shrimp. The pmo-miR-bantam regulates PmKuSPI post-transcriptionally and affects shrimp susceptibility to WSSV infection through hemocyte homeostasis.