Heat shock protein 90 of Pacific white shrimp (Litopenaeus vannamei) is possibly involved in promoting white spot syndrome virus infection

Transcriptional dynamics during Heliothis zea nudivirus 1 infection in an ovarian cell line from Helicoverpa zea

Nudiviruses (family Nudiviridae) are double-stranded DNA viruses that infect various insects and crustaceans. Among them, Heliothis zea nudivirus 1 (HzNV-1) represents the rare case of a lepidopteran nudivirus inducing a sexual pathology. Studies about molecular pathological dynamics of HzNV-1 or other nudiviruses are scarce. Hence, this study aims to provide a transcriptomic profile of HzNV-1 in an ovary-derived cell line of Helicoverpa zea (HZ-AM1), during early (3, 6 and 9 h post-infection) and advanced (12 and 24 h post-infection) stages of infection. Total RNA was extracted from both virus- and mock-infected cells, and RNA-seq analysis was performed to examine both virus and host transcriptional dynamics. Hierarchical clustering was used to categorize viral genes, while differential gene expression analysis was utilized to pinpoint host genes that are significantly affected by the infection. Hierarchical clustering classified the 154 HzNV-1 genes into four temporal phases, with early phases mainly involving transcription and replication genes and later phases including genes for virion assembly. In addition, a novel viral promoter motif was identified in the upstream region of early-expressed genes. Host gene analysis revealed significant upregulation of heat shock protein genes and downregulation of histone genes. The identification of temporal patterns in viral gene expression enhances the molecular understanding of nudivirus pathology, while the identified differentially expressed host genes highlight the key pathways most hijacked by HzNV-1 infection.

In silico identification and functional study of long non-coding RNA involved in acute hepatopancreatic necrosis disease caused by Vibrio parahaemolyticus infection in white shrimp, Litopenaeus vannamei

Acute hepatopancreatic necrosis disease (AHPND) caused by toxin-producing Vibrio parahaemolyticus (VpAHPND) has severely affected shrimp production. Long non-coding RNA (lncRNA), a regulatory non-coding RNA, which can play important function in shrimp disease responses. This study aimed to identify and investigate the role of lncRNA involved in VpAHPND infection in Pacific white shrimp, Litopenaeus vannamei. From a total of 368,736 de novo assembled transcripts, 67,559 were identified as putative lncRNAs, and only 72 putative lncRNAs showed differential expression between VpAHPND-infected and normal shrimp. The six candidate lncRNAs were validated for their expression profiles during VpAHPND infection and tissue distribution using RT-qPCR. The role of lnc2088 in response to VpAHPND infection was investigated through RNA interference. The result indicated that the suppression of lnc2088 expression led to an increase in shrimp mortality after VpAHPND infection. To explore the set of genes involved in lnc2088 knockdown, RNA sequencing was performed. A total of 275 differentially expressed transcripts were identified in the hepatopancreas of lnc2088 knockdown shrimp. The expression profiles of five candidate metabolic and immune-related genes were validated in lnc2088 knockdown and VpAHPND-infected shrimp. The result showed that the expression of ChiNAG was significantly increased, while that of NCBP1, WIPF2, and NFKB1 was significantly downregulated in ds2088-injected shrimp. Additionally, the expression of NFKB1, NCBP1 and WIPF2 was significantly increased, whereas that of ChiNAG and CUL5 were significantly decreased after infection with VpAHPND. Our work identified putative lncRNA profiles in L. vannamei in response to VpAHPND infection and investigated the role of lncRNA in shrimp immunity.

Litopenaeus vannamei heat shock protein 90 (LvHSP90) interacts with white spot syndrome virus protein, WSSV322, to modulate hemocyte apoptosis during viral infection

As cellular chaperones, heat shock protein can facilitate viral infection in different steps of infection process. Previously, we have shown that the suppression of Litopenaeus vannamei (Lv)HSP90 not only results in a decline of white spot syndrome virus (WSSV) infection but also induces apoptosis in shrimp hemocyte cells. However, the mechanism underlying how LvHSP90 involved in WSSV infection remains largely unknown. In this study, a yeast two-hybrid assay and co-immunoprecipitation revealed that LvHSP90 interacts with the viral protein WSSV322 which function as an anti-apoptosis protein. Recombinant protein (r) LvHSP90 and rWSSV322 inhibited cycloheximide-induced hemocyte cell apoptosis in vitro. Co-silencing of LvHSP90 and WSSV322 in WSSV-infected shrimp led to a decrease in expression level of viral replication marker genes (VP28, ie-1) and WSSV copy number, while caspase 3/7 activity was noticeably induced. The number of apoptotic cells, confirmed by Hoechst 33342 staining assay and annexin V/PI staining, was significantly higher in LvHSP90 and WSSV322 co-silenced-shrimp than the control groups. Moreover, the co-silencing of LvHSP90 and WSSV322 triggered apoptosis by the mitochondrial pathway, resulting in the upregulation of pro-apoptotic protein expression (bax) and the downregulation of anti-apoptotic protein expression (bcl, Akt). This process also involved the release of cytochrome c (CytC) from the mitochondria and a decrease in mitochondrial membrane potential (MMP). These findings suggest that LvHSP90 interacts with WSSV322 to facilitate viral replication by inhibiting host apoptosis during WSSV infection.

Involvement of transcriptional co-activator p300 in upregulated expression of HSP70 by aquareovirus non-structural protein NS31

Members of Aquareovirus genus, including grass carp reovirus (GCRV), contribute to a serious threat to aquaculture animals accompanied by stress response. Our previous reports revealed that GCRV nonstructural protein NS31 serves as a potent contributor for virus selectively up-regulating specific heat shock protein 70-kd gene（HSP70），however，the mechanism by which inducing HSP70 gene expression is unknown. In this study, we further found that either the N- or C-terminal domain of GCRV NS31 is responsible for enhancing fish HSP70 promoter transcription, and recombinant NS31 protein purified from baculovirus expression system seems to not directly bind HSP70 basic promoter in vitro by an electrophoretic mobility shift assay. However, the transcriptional co-activator p300 was identified as a potential interacting partner for NS31 by pull-down assay. Moreover, knock-down of p300 or addition of p300 inhibitor resulted in obviously reduced HSP70 expression by NS31 or GCRV infection suggesting that the well-characterized heat-shock-responsive HSF1/p300 transcriptional complex might involve in the induction of HSP70. These results collectively reveal this aquareovirus generates cell stress response through its nonstructural protein NS31 recruiting transcriptional co-activator p300.

Transcriptome analysis of Fenneropenaeus merguiensis in response to Vibrio proteolyticus infection

In recent years, due to the destruction of the culture environment and serious ecological pressure, especially in the process of culture, residual bait, faeces and fishery drug abuse will lead to the accumulation of harmful metabolites such as ammonia nitrogen and nitrite, and biological denitrification is the most economical and effective method to remove the single. Therefore, in this study, a nitrite removal strain XA19 was isolated and screened from a shrimp biofloc culture pond. This strain was identified as a clade of Vibrio proteolyticus because the homology between XA19 and V. proteolyticus WDVP was as high as 99.86% by using 16S rDNA gene sequence analysis and NCBI database comparison. Scanning electron microscopy images showed that V. proteolyticus is short-rod-shaped with a curved body and no budding spores, pods and flagella. Antimicrobial susceptibility test proved that V. proteolyticus was resistant to ampicillin, oxacillin, penicillin, vancomycin and clindamycin. In the median lethal concentration 50 (LC50 ) test, at 7-day post-infection (dpi), LC50 of V. proteolyticus for Fenneropenaeus merguiensis was 1.69 × 104  CFU/mL. Transcriptome sequencing analysis was carried out on hepatopancreas of F. merguiensis at 24 and 48 hpi. A total of 176 differentially expressed genes (DEGs) were screened at 24 hpi, including 104 up-regulated DEGs and 72 down-regulated DEGs, and a total of 52 DEGs were screened at 48 hpi, including 32 up-regulated DEGs and 20 down-regulated DEGs. In the Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analysis of DEGs, many immune-related signalling pathways were significantly enriched, including Hippo signalling pathway, phagosome, Toll and Imd signalling pathways and Wnt signalling pathway. In addition, some pathways related to Warburg effect were also enriched, including Glycolysis/Gluconeogenesis, Biosynthesis of amino acids, amino sugar and nucleotide sugar metabolism and so on. In this study, the toxicity and drug sensitivity of V. proteolyticus were systematically studied, and the immune response of hepatopancreas of F. merguiensis to V. proteolyticus infection was preliminarily revealed from the molecular level. The results may provide a reference for the prevention and control of V. proteolyticus.

DnaJC16, the molecular chaperone, is implicated in hemocyte apoptosis and facilitates of WSSV infection in shrimp

Chaperone proteins, including heat shock proteins (HSPs) and DnaJ proteins, are highly conserved and well known for their quick responses to environmental stresses and pathogen infections, especially viruses. However, how DnaJ, an HSP family member, in Penaeus vannamei responds to viral invasion has not been reported. In this research, the novel DnaJ homolog subfamily C member 16-like, or DnaJC16, was characterized in P. vannamei. It contains the DnaJ and thioredoxin domains. Phylogenetic tree analysis demonstrated the conservation of DnaJC16 among penaeid shrimp, where PvDnaJC16 was found to be closely related to DnaJC16 from Fenneropenaeus chinensis and Marsupenaeus japonicus. The transcripts of PvDnaJC16 were expressed in all the tissues tested, and the highest expression was in the lymphoid organs. As hemocytes are major immune tissue, we found significant upregulation of PvDnaJC16 in shrimp hemocytes after white spot syndrome virus (WSSV) infection. Furthermore, the suppression of PvDnaJC16 expression by RNA interference in WSSV-infected shrimp showed a decrease in replication and WSSV copy number. Interestingly, a dramatically high cumulative survival rate following the WSSV challenge (over 60%) was observed in PvDnaJC16-silenced shrimp. Meanwhile, the total hemocyte number was significantly increased in PvDnaJC16 knockdown. In addition, the expression of caspase-3 was reduced, as was the caspase-3/7 activity in PvDnaJC16 silencing. Additionally, the percentage of late apoptotic hemocytes diminished after PvDnaJC16 reduction, whereas the percentage of hemocyte viability increased. Our data reflect the fact that the upregulation of PvDnaJC16 expression upon WSSV infection enhances hemocyte apoptosis, which can accelerate viral spreading in shrimp.