Dystrophin gene expression and intracellular calcium changes in the giant freshwater prawn, Macrobrachium rosenbergii, in response to white spot symptom disease infection

Unveiling the impact of shrimp piRNAs on WSSV infection and immune modulation

Piwi-interacting RNAs (piRNAs) are small non-coding RNAs that play a crucial role in gene regulation and immune defense. This study investigates their function in Penaeus vannamei shrimp during White Spot Syndrome Virus (WSSV) infection. Analysis of small RNA libraries from WSSV-infected shrimp hemocytes identified 82,788 piRNA homologs, with 138 showing altered expression during infection. Putative piRNAs were mapped to both the P. vannamei nuclear and mitochondrial genomes, highlighting their diverse origins. Interestingly, some piRNA sequences from uninfected shrimp mapped to both the shrimp and WSSV genomes, suggesting potential subversion or integration of viral fragments into the host genome. We focused on piR-pva-926938, a downregulated piRNA targeting the WSSV186 gene. Introducing piR-pva-926938 into WSSV-infected shrimp suppressed WSSV186 expression, but paradoxically increased viral load by downregulating host immune genes like calcineurin B and dynamin-binding protein. This study is the first to report WSSV-responsive piRNAs in shrimp and reveals the complex interplay between piRNAs, viral genes, and host immunity during WSSV infection.

WSSV exploits AMPK to activate mTORC2 signaling for proliferation by enhancing aerobic glycolysis

AMPK plays significant roles in the modulation of metabolic reprogramming and viral infection. However, the detailed mechanism by which AMPK affects viral infection is unclear. The present study aims to determine how AMPK influences white spot syndrome virus (WSSV) infection in shrimp (Marsupenaeus japonicus). Here, we find that AMPK expression and phosphorylation are significantly upregulated in WSSV-infected shrimp. WSSV replication decreases remarkably after knockdown of Ampkα and the shrimp survival rate of AMPK-inhibitor injection shrimp increases significantly, suggesting that AMPK is beneficial for WSSV proliferation. Mechanistically, WSSV infection increases intracellular Ca2+ level, and activates CaMKK, which result in AMPK phosphorylation and partial nuclear translocation. AMPK directly activates mTORC2-AKT signaling pathway to phosphorylate key enzymes of glycolysis in the cytosol and promotes expression of Hif1α to mediate transcription of key glycolytic enzyme genes, both of which lead to increased glycolysis to provide energy for WSSV proliferation. Our findings reveal a novel mechanism by which WSSV exploits the host CaMKK-AMPK-mTORC2 pathway for its proliferation, and suggest that AMPK might be a target for WSSV control in shrimp aquaculture.

Potential muscle activity disturbance in Penaeus monodon during Acute Hepatopancreatic Necrosis Disease (AHPND) infection: Inference through gene expression, calcium concentration, and MicroRNA

Global shrimp aquaculture farmers have suffered major economic losses due to disease outbreaks. A notable shrimp disease is Acute Hepatopancreatic Necrosis Disease (AHPND), which is caused by a new strain of Vibrio parahaemolyticus bacteria (Vp_AHPND) that mainly inhabits the shrimp gut and damages the hepatopancreas. Fewer studies have investigated whether this disease will affect shrimp muscle functioning or cause any muscle damage. We challenged Penaeus monodon shrimp with Vp_AHPND bacteria using an immersion method. Expression of Dystrophin gene, an important regulatory gene for maintenance of muscle integrity, was quantified from muscle samples using qRT-PCR. Additional verification was conducted by determining calcium concentration and bta-miR-4286 and dre-miR-107b miRNAs expression. P. monodon dystrophin gene demonstrated the highest expression level during AHPND infection when muscle calcium concentration was detected at its lowest level at 6 h post-infection (hpi). The highest muscle calcium concentration, determined at 36 hpi, was supported by higher bta-miR-4286 miRNA expression and lower dre-miR-107b miRNA expression in Vp_AHPND-infected samples compared to uninfected samples at the same time point. We deduced an interactive relationship between dystrophin gene expression, calcium concentration, and miRNA expression in P. monodon muscle tissues triggered by the invading Vp_AHPND bacterium.

Downregulation of dystrophin expression in pupae of the whitefly Bemisia tabaci inhibits the emergence of adults

The whitefly Bemisia tabaci is a major pest to agriculture. Adults are able to fly for long distances and to colonize staple crops, herbs and ornamentals, and to vector viruses belonging to several important taxonomic groups. During their early development, whiteflies mature from eggs through several nymphal stages (instars I to IV) until adults emerge from pupae. We aim at reducing whitefly populations by inhibiting the emergence of adults from nymphs. Here we targeted dystrophin, a conserved protein essential for the development of the muscle system in humans, other animals and insects. We have exploited the fact that whitefly nymphs developing on tomato leaves feed from the plant phloem via their stylets. Thus, we delivered dystrophin-silencing double-stranded RNA to nymphs developing on leaves of tomato plantlets with their roots bathing in the silencing solution. Downregulation of dystrophin expression occurred mainly in pupae. Dystrophin silencing induced also the downregulation of the dystrophin-associated protein genes actin and tropomyosin, and disrupted F-actin. Most significantly, the treatment inhibited the emergence of adults from pupae, suggesting that targeting dystrophin may help to restrain whitefly populations. This study demonstrates for the first time the important role of dystrophin in the development of a major insect pest to agriculture.