RNAi screening identifies a new Toll from shrimp Litopenaeus vannamei that restricts WSSV infection through activating Dorsal to induce antimicrobial peptides

Abstract

The function of Toll pathway defense against bacterial infection has been well established in shrimp, however how this pathway responds to viral infection is still largely unknown. In this study, we report the Toll4-Dorsal-AMPs cascade restricts the white spot syndrome virus (WSSV) infection of shrimp. A total of nine Tolls from Litopenaeus vannamei namely Toll1-9 are identified, and RNAi screening in vivo reveals the Toll4 is important for shrimp to oppose WSSV infection. Knockdown of Toll4 results in elevated viral loads and renders shrimp more susceptible to WSSV. Furthermore, Toll4 could be a one of upstream pattern recognition receptor (PRR) to detect WSSV, and thereby leading to nuclear translocation and phosphorylation of Dorsal, the known NF-κB transcription factor of the canonical Toll pathway. More importantly, silencing of Toll4 and Dorsal contributes to impaired expression of a specific set of antimicrobial peptides (AMPs) such as anti-LPS-factor (ALF) and lysozyme (LYZ) family, which exert potent anti-WSSV activity. Two AMPs of ALF1 and LYZ1 as representatives are demonstrated to have the ability to interact with several WSSV structural proteins to inhibit viral infection. Taken together, we therefore identify that the Toll4-Dorsal pathway mediates strong resistance to WSSV infection by inducing some specific AMPs.

RPS27, a sORF-Encoded Polypeptide, Functions Antivirally by Activating the NF-κB Pathway and Interacting With Viral Envelope Proteins in Shrimp

“…In Litopenaeus vannamei, the silence of Dorsal leads to a decline in the expression of a specific group of AMPs, such as the anti-lipopolysaccharide factor (ALF) and lysozyme (LYZ) family. Meanwhile, ALF1 and LYZ1 have been shown to interact with several WSSV structural proteins to inhibit viral infection (40). In other studies, the Toll and IMD pathways in shrimp are activated and AMP are induced after WSSV infection.…”

“…To test whether the expression of MjRPS27 could be suppressed, we injected different amounts of dsRNA (40,80, and 100 µg) into shrimp at the penultimate somite, and an equal amount of GFP dsRNA injection was used as the control. At 48 h post injection, the MjRPS27 expression in gills and intestine was analyzed by qPCR to confirm the RNA interference (RNAi) efficiency.…”

Identification and Molecular Characterization of a Pellino Protein in Kuruma Prawn (Marsupenaeus Japonicus) in Response to White Spot Syndrome Virus and Vibrio Parahaemolyticus Infection

“…In shrimp, WSSV activates the Toll and IMD signaling pathways, which are two NF-κB signaling pathways [39]. The role of the mRNA expression level of Pellino is the focus of most previous studies.…”

Penaeidins are a novel family of antiviral effectors against WSSV in shrimp

“…At 48 h post injection, three samples of hemocytes were collected from 15 shrimps (5 shrimps each sample). The method of total RNA extraction, cDNA synthesis and qRT-PCR analysis was performed as described (18). All samples were tested in triplicate.…”

“…In addition, α-defensin peptides can neutralize herpes simplex virus 1 (HSV-1) by binding to natural viral glycoproteins (17). In shrimps, so far, the ALFs and LYZs have been demonstrated to exhibit anti-WSSV activities by binding to WSSV structural proteins (18). Until now, although penaeidins have not be reported to inhibit any viruses, the mRNA levels of PmPEN5 from Penaeus monodon were significantly induced when an infection with WSSV, suggesting its possible role in shrimp antiviral immunity (19).…”