Shrimp miRNAs regulate innate immune response against white spot syndrome virus infection

Participation of shrimp pva-miR-166 in hemocyte homeostasis by modulating apoptosis-related gene PvProsaposin during white spot syndrome virus infection

Tiny controllers referred to as microRNAs (miRNAs) impede the expression of genes to modulate biological processes. In invertebrates, particularly in shrimp as a model organism, it has been demonstrated that miRNAs play a crucial role in modulating innate immune responses against viral infection. By analyzing small RNAs, we identified 60 differentially expressed miRNAs (DEMs) in Penaues vannamei hemocytes following infection with white spot syndrome virus (WSSV). We predicted the target genes of WSSV-responsive miRNAs, shedding light on their participation in diverse biological pathways. We are particularly intrigued by pva-miR-166, which is the most notably elevated miRNA among 60 DEMs. At 24 h post-infection (hpi), the negative correlation between the expression of pva-miR-166 and its target gene, PvProsaposin, was evident and their interaction was confirmed by a reduction in luciferase activity in vitro. Suppression of PvProsaposin in unchallenged shrimp led to decreased survival rates, reduced total hemocyte count (THC), and increased caspase 3/7 activity, suggesting its significant role in maintaining hemocyte homeostasis. In WSSV-infected shrimp, a lower number of hemocytes corresponded to a lower WSSV load, but higher shrimp mortality was observed when PvProsaposin was suppressed. Conformingly, the introduction of the pva-miR-166 mimic to WSSV-infected shrimp resulted in decreased levels of PvProsaposin transcripts, a significant loss of THC, and an increase in the hemocyte apoptosis. Taken together, we propose that pva-miR-166 modulates hemocyte homeostasis during WSSV infection by suppressing the PvProsaposin, an anti-apoptotic gene. PvProsaposin inhibition disrupts hemocyte homeostasis, rendering the shrimp's inability to withstand WSSV invasion.IMPORTANCEGene regulation by microRNAs (miRNAs) has been reported during viral infection. Furthermore, hemocytes serve a dual role, not only producing various immune-related molecules to combat viral infections but also acting as a viral replication site. Maintaining hemocyte homeostasis is pivotal for the shrimp's survival during infection. The upregulated miRNA pva-miR-166 could repress PvProsaposin expression in shrimp hemocytes infected with WSSV. The significance of PvProsaposin in maintaining hemocyte homeostasis via apoptosis led to reduced survival rate, decreased total hemocyte numbers, and elevated caspase 3/7 activity in PvProsaposin-silenced shrimp. Additionally, the inhibitory ability of pva-miR-166-mimic and dsRNA-PvProsaposin on the expression of PvProsaposin also lowered the THC, increases the hemocyte apoptosis, resulting in a lower WSSV copy number. Ultimately, the dysregulation of the anti-apoptotic gene PvProsaposin by pva-miR-166 during WSSV infection disrupts hemocyte homeostasis, leading to an immunocompromised state in shrimp, rendering them incapable of surviving WSSV invasion.

High-Temperature-Induced Differential Expression of miRNA Mediates Liver Inflammatory Response in Tsinling Lenok Trout (Brachymystax lenok tsinlingensis)

High-temperature stress poses a significant environmental challenge for aquatic organisms, including tsinling lenok trout (Brachymystax lenok tsinlingensis). This study aimed to investigate the role of microRNAs (miRNAs) in inducing liver inflammation in tsinling lenok trout under high-temperature stress. Tsinling lenok trout were exposed to high-temperature conditions (24 °C) for 8 h, and liver samples were collected for analysis. Through small RNA sequencing, we identified differentially expressed miRNAs in the liver of high-temperature-stressed tsinling lenok trout compared to the control group (maintained at 16 °C). Several miRNAs, including novel-m0105-5p and miR-8159-x, showed significant changes in expression levels. Additionally, we conducted bioinformatics analysis to explore the potential target genes of these differentially expressed miRNAs. Our findings revealed that these miRNA target genes are involved in inflammatory response pathways, such as NFKB1 and MAP3K5. The downregulation of novel-m0105-5p and miR-8159-x in the liver of high-temperature-stressed tsinling lenok trout suggests their role in regulating liver inflammatory responses. To validate this, we performed a dual-luciferase reporter assay to confirm the regulatory relationship between miRNAs and target genes. Our results demonstrated that novel-m0105-5p and miR-8159-x enhance the inflammatory response of hepatocytes by promoting the expression of NFKB1 and MAP3K5, respectively. In conclusion, our study provides evidence that high-temperature stress induces liver inflammation in tsinling lenok trout through dysregulation of miRNAs. Understanding the molecular mechanisms underlying the inflammatory response in tsinling lenok trout under high-temperature stress is crucial for developing strategies to mitigate the negative impacts of environmental stressors on fish health and aquaculture production.

MicroRNA sequencing analysis reveals immune responses in hepatopancreas of Fenneropenaeus penicillatus under white spot syndrome virus infection

White Spot Disease is one of the most harmful diseases of the red tail shrimp, which can cause devastating economic losses due to the highest mortality up to 100% within a few days. MicroRNAs (miRNAs) are large class of small noncoding RNAs with the ability to post-transcriptionally repress the translation of target mRNAs. MiRNAs are considered to have a significant role in the innate immune response of crustaceans, particularly in relation to antiviral defense mechanisms. Numerous crustacean miRNAs have been verified to be required in host immune defense against viral infection, however, till present, the miRNAs functions of F. penicillatus defense WSSV infection have not been studied yet. Here in this study, for the first time, miRNAs involved in the F. penicillatus immune defense against WSSV infection were identified using high-throughput sequencing platform. A total of 432 miRNAs were obtained including 402 conserved miRNAs and 30 novel predicted miRNAs. Comparative analysis between the WSSV-challenged group and the control group revealed differential expression of 159 microRNAs in response to WSSV infection. Among these, 48 were up-regulated and 111 were down-regulated. Ten candidate MicroRNAs associated with immune activities were randomly selected for qRT-PCR analysis, which confirming the expression profiling observed in the MicroRNA sequencing data. As a result, most differentially expressed miRNAs were down-regulated lead to increase the expression of various target genes that mediated immune reaction defense WSSV infection, including genes related to signal transduction, Complement and coagulation cascade, Phagocytosis, and Apoptosis. Furthermore, the genes expression of the key members in Toll and Imd signaling pathways and apoptotic signaling were mediated by microRNAs to activate host immune responses including apoptosis against WSSV infection. These results will help to understand molecular defense mechanism against WSSV infection in F. penicillatus and to develop an effective WSSV defensive strategy in shrimp farming.

MicroRNA sequencing analysis reveals injury-induced immune responses of Scylla paramamosain against cheliped autotomy

During pond culture or intensive culture system of crabs (mainly Eriocheir sinensis, Portunus trituberculatus and Scylla paramamosain), high-density farming has typically contributed to a higher limb autotomy level in juvenile animals, especially in S. paramamosain which has a high level of cannibalism. Due to the high limb autotomy level, the survival and growth rates in S. paramamosain farming are restricted, which limit the growth of the mud crab farming industry. MicroRNAs (miRNAs) are small noncoding RNAs that regulate a series of biological processes including innate immune responses by post-transcriptional suppression of their target genes. MiRNAs are believed to be crucial for innate immune process of host wound healing. Many miRNAs have been verified to be required in host immune responses to repair wound and to defense pathogen after tissue damage. However, to our best knowledge, the miRNAs functions of crustacean innate immune reactions against injury induced by limb autotomy have not been studied yet. Here in this study, for the first time, miRNAs involved in the S. paramamosain immune reactions against injury induced by cheliped autotomy were obtained by high-throughput sequencing. A total of 575 miRNAs (518 known miRNAs and 57 novel predicted miRNAs) were obtained, of which 141 differentially expressed microRNAs (93 up-regulated microRNAs and 48 down-regulated microRNAs) were revealed to be modified against cheliped autotomy, and the qPCR results of randomly selected miRNAs confirmed the expression patterns in the miRNAs sequencing data. Numerous immune-related target genes associated with innate immune system were mediated by miRNAs to induce host humoral immune and cellular immune defense to minimize acute physical damage. Furthermore, the genes expression in hemolymph coagulation and melanization pathways, as well as Toll and Imd signaling pathways were mediated by miRNAs to activate host immune responses including melanization and antimicrobial peptides for rapid wound healing and killing invaded pathogens. These results will help to understand injury-induced immune responses in crabs and to develop an effective control strategy of autotomy rate in crabs farming.

Epigenetic Modulations for Prevention of Infectious Diseases in Shrimp Aquaculture

Aquaculture assumes a pivotal role in meeting the escalating global food demand, and shrimp farming, in particular, holds a significant role in the global economy and food security, providing a rich source of nutrients for human consumption. Nonetheless, the industry faces formidable challenges, primarily attributed to disease outbreaks and the diminishing efficacy of conventional disease management approaches, such as antibiotic usage. Consequently, there is an urgent imperative to explore alternative strategies to ensure the sustainability of the industry. In this context, the field of epigenetics emerges as a promising avenue for combating infectious diseases in shrimp aquaculture. Epigenetic modulations entail chemical alterations in DNA and proteins, orchestrating gene expression patterns without modifying the underlying DNA sequence through DNA methylation, histone modifications, and non-coding RNA molecules. Utilizing epigenetic mechanisms presents an opportunity to enhance immune gene expression and bolster disease resistance in shrimp, thereby contributing to disease management strategies and optimizing shrimp health and productivity. Additionally, the concept of epigenetic inheritability in marine animals holds immense potential for the future of the shrimp farming industry. To this end, this comprehensive review thoroughly explores the dynamics of epigenetic modulations in shrimp aquaculture, with a particular emphasis on its pivotal role in disease management. It conveys the significance of harnessing advantageous epigenetic changes to ensure the long-term viability of shrimp farming while deliberating on the potential consequences of these interventions. Overall, this appraisal highlights the promising trajectory of epigenetic applications, propelling the field toward strengthening sustainability in shrimp aquaculture.

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 modulating 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 luciferase 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 posttranscriptionally controlled by pmo-miR-bantam and plays a role in hemocyte homeostasis, which in turn affects shrimp susceptibility to WSSV infection.

MicroRNA Regulation in Infectious Diseases and Its Potential as a Biosensor in Future Aquaculture Industry: A Review

An infectious disease is the most apprehensive problem in aquaculture as it can lead to high mortality in aquatic organisms and massive economic loss. Even though significant progress has been accomplished in therapeutic, prevention, and diagnostic using several potential technologies, more robust inventions and breakthroughs should be achieved to control the spread of infectious diseases. MicroRNA (miRNA) is an endogenous small non-coding RNA that post-transcriptionally regulates the protein-coding genes. It involves various biological regulatory mechanisms in organisms such as cell differentiation, proliferation, immune responses, development, apoptosis, and others. Furthermore, an miRNA also acts as a mediator to either regulate host responses or enhance the replication of diseases during infection. Therefore, the emergence of miRNAs could be potential candidates for the establishment of diagnostic tools for numerous infectious diseases. Interestingly, studies have revealed that miRNAs can be used as biomarkers and biosensors to detect diseases, and can also be used to design vaccines to attenuate pathogens. This review provides an overview of miRNA biogenesis and specifically focuses on its regulation during infection in aquatic organisms, especially on the host immune responses and how miRNAs enhance the replication of pathogens in the organism. In addition to that, we explored the potential applications, including diagnostic methods and treatments, that can be employed in the aquaculture industry.

Transcriptome-based insights into the regulatory role of immune-responsive circular RNAs in Litopanaeus vannamei upon WSSV infection

Circular RNAs (circRNAs) are non-coding RNAs (ncRNAs) originating from a post-transcriptional modification process called back-splicing. Despite circRNAs being traditionally considered by-products rather than independently functional, circRNAs play many vital roles, such as in host immunity during viral infection. However, in shrimp, these remain largely unexplored. Therefore, this study aims to identify circRNAs in Litopenaeus vannamei in the context of WSSV infection, one of the most eradicative pathogens threatening shrimp populations worldwide. We identified 290 differentially expressed circRNAs (DECs) in L. vannamei upon WSSV infection. Eight DECs were expressed from their parental genes, including alpha-1-inhibitor-3, calpain-B, integrin-V, hemicentin-2, hemocytin, mucin-17, proPO2, and rab11-FIP4. These were examined quantitatively by qRT-PCR, which revealed the relevant expression profiles to those obtained from circRNA-Seq. Furthermore, the structural and chemical validation of the DECs conformed to the characteristics of circRNAs. One of the functional properties of circRNAs as a miRNA sponge was examined via the interaction network between DECs and WSSV-responsive miRNAs, which highlighted the targets of miRNA sponges. Our discovery could provide insight into the participation of these ncRNAs in shrimp antiviral responses.

Shrimp pmo-miR-750 regulates the expression of sarcoplasmic calcium-binding protein facilitating virus infection in Penaeus monodon

MicroRNAs (miRNAs) regulate gene expression post-transcriptionally and play crucial roles in antiviral responses. Penaeus monodon miR-750 (pmo-miR-750) was found to be strongly up-regulated in the late phase of white spot syndrome virus (WSSV) infection, but its function remains uncharacterized. Herein, the targets that were translationally down-regulated in the shrimp stomach following a pmo-miR-750 mimic injection were identified using two-dimensional gel electrophoresis. Sarcoplasmic calcium-binding protein (Scp) and actin1 (Act1) were revealed to be down-regulated protein spots. The genuine binding of pmo-miR-750 mimic to Scp but not Act1 mRNA was validated in vitro. In addition, a negative correlation between the Scp transcript and pmo-miR-750 expression level in WSSV-infected P. monodon stomach implies that pmo-miR-750 regulates Scp expression in vivo. When injected into WSSV-infected shrimp, the pmo-miR-750 mimic suppressed Scp expression but significantly increased the WSSV copy number. Consistent with the miRNA mimic-mediated Scp suppression, the loss of function assay of Scp in WSSV-challenged shrimp by RNA interference revealed a decreased survival rate with a dramatic increase in viral copy number. Besides that, apoptosis was activated in the hemocytes of the Scp knockdown shrimp upon WSSV infection. Collectively, our findings reveal that up-regulated pmo-miR-750 suppresses Scp expression at both the transcript and protein levels in the late stage of WSSV infection, which contributes to modulating apoptosis and eventually enabling viral propagation.

Cellular Lnc_209997 suppresses Bombyx mori nucleopolyhedrovirus replication by targeting miR-275-5p in B. mori

Long non-coding RNA (lncRNA) is a type of non-coding RNA molecule, which exceeds 200 nucleotides in length and participates in the regulation of a variety of life activities. Recent studies showed that lncRNAs play important roles in viral infection and host immunity. At present, the researches on insect lncRNAs are relatively few. In this study, we found the expression of Lnc_209997 was significantly down-regulated in silkworm fat body infected with Bombyx mori nucleopolyhedrosis virus (BmNPV). Inhibition of Lnc_209997 promoted BmNPV replication. Enhancing the expression of Lnc_209997 inhibited the proliferation of BmNPV. miR-275-5p was up-regulated in silkworm fat body infected with BmNPV. Dual luciferase reporter gene system confirmed the interaction between Lnc_209997 and miR-275-5p. Over-expression of Lnc_209997 inhibited the expression of miR-275-5p, while inhibition of Lnc_209997 enhanced the expression of miR-275-5p. Further, over-expression of miR-275-5p can facilitate the replication of BmNPV. These results suggested that BmNPV could increase the expression of miR-275-5p by inhibiting cellular Lnc_209997 expression to promote their own proliferation. Our results are helpful for better understanding the role of lncRNAs in BmNPV infection, and provide insights into elucidating the molecular mechanism of interaction between Bombyx mori and virus.

Identification and characterization of novel microRNAs in disease-resistant and disease-susceptible Penaeus monodon

MicroRNAs (miRNAs), known as a translational regulator, are evolutionary conserved, small, and noncoding RNA. They have played a vital role in disease biology through the host-virus-miRNA-interaction. In this study, novel miRNAs of naturally occurring, virus-free disease-resistant and disease-susceptible Penaeus monodon were identified and characterized. In disease-susceptible samples, 45 homologous mature miRNAs and 28 homologous precursor miRNAs were identified. In disease-resistant samples, 52 homologous mature miRNAs and 87 homologous precursor miRNAs were identified. In disease-susceptible samples, 33 novel mature miRNAs and 33 novel precursor miRNAs were identified. In disease-resistant samples, 523 novel mature miRNAs and 141 novel precursor miRNAs were identified. Differential expression study revealed the up-regulated and down-regulated miRNAs in disease-resistant and disease-susceptible P. monodon. Gene ontology pathway of known and novel miRNAs revealed that P. monodon miRNAs might have a potential and specific role in signal transduction, cell-to-cell signaling, innate immune response and defense response to different pathogens.

MicroRNA-315-5p promotes rice black-streaked dwarf virus infection by targeting a melatonin receptor in the small brown planthopper

BACKGROUND

MicroRNAs (miRNAs), a class of small non-coding endogenous RNAs, play key roles in various biological processes. Most plant viruses are transmitted by insect vectors. However, little is known about the function of miRNAs on plant virus-insect host interaction.

RESULTS

We investigated the role of miR-315-5p in regulation of plant viral infection in insects using a rice black-streaked dwarf virus (RBSDV) and small brown planthopper (SBPH) interaction system. Our results showed that miR-315-5p had the highest expression level in 2nd-instar nymph, and was highly expressed in the salivary gland and midgut in SBPH. miR-315-5p was in response to and regulated RBSDV infection in SBPH. Injection of miR-315-5p mimic, agomir-315, significantly increased the RBSDV accumulation, whereas injection of miR-315-5p inhibitor, antagomir-315, reduced virus accumulation in SBPH. Furthermore, a melatonin receptor was identified as a target gene of miR-315-5p by the dual luciferase reporter assay. Knockdown of the melatonin receptor significantly increased the expression of RBSDV coat protein gene S10 and replication related genes, S5-1, S6, and S9-1. Furthermore, treatment with melatonin receptor antagonist luzindole and activator agomelatine significantly increased and reduced RBSDV accumulation in SBPH, respectively. Compared to the control, miR-315-5p did not affect the efficiency of RBSDV acquisition in SBPH. However, the efficiency of RBSDV transmission was significantly reduced after injecting antagomir-315.

CONCLUSION

Taken together, our data reveal that miR-315-5p is beneficial for RBSDV infection in its insect vector by directly targeting a melatonin receptor. These findings provide a new insight to the function of miRNAs in virus-insect vector interaction. © 2021 Society of Chemical Industry.

Global mRNA and miRNA Analysis Reveal Key Processes in the Initial Response to Infection with WSSV in the Pacific Whiteleg Shrimp

White Spot Disease (WSD) presents a major barrier to penaeid shrimp production. Mechanisms underlying White Spot Syndrome Virus (WSSV) susceptibility in penaeids are poorly understood due to limited information related to early infection. We investigated mRNA and miRNA transcription in Penaeus vannamei over 36 h following infection. Over this time course, 6192 transcripts and 27 miRNAs were differentially expressed—with limited differential expression from 3–12 h post injection (hpi) and a more significant transcriptional response associated with the onset of disease symptoms (24 hpi). During early infection, regulated processes included cytoskeletal remodelling and alterations in phagocytic activity that may assist WSSV entry and translocation, novel miRNA-induced metabolic shifts, and the downregulation of ATP-dependent proton transporter subunits that may impair cellular recycling. During later infection, uncoupling of the electron transport chain may drive cellular dysfunction and lead to high mortalities in infected penaeids. We propose that post-transcriptional silencing of the immune priming gene Dscam (downregulated following infections) by a novel shrimp miRNA (Pva-pmiR-78; upregulated) as a potential mechanism preventing future recognition of WSSV that may be suppressed in surviving shrimp. Our findings improve our understanding of WSD pathogenesis in P. vannamei and provide potential avenues for future development of prophylactics and treatments.

Stress responses in expressions of microRNAs in mussel Mytilus galloprovincialis exposed to cadmium

MicroRNAs (miRNAs) are known to have complicated functions in aquatic species, but little is known about the role of miRNAs in mollusk species under environmental stress. In this study, we performed small RNA sequencing to characterize the differentially expressed miRNAs in different tissues (whole tissues, digestive glands, gills, and gonads) of blue mussels (Mytilus galloprovincialis) exposed to cadmium (Cd). In summary, 107 known miRNAs and 32 novel miRNAs were significantly (p < 0.01) differentially expressed after Cd exposure. The peak size of miRNAs was 22 nucleotides. Target genes of these differentially expressions of miRNAs related to immune defense, apoptosis, lipid and xenobiotic metabolism showed significant changes under Cd stress. These findings provide the first characterization of miRNAs in mussel M. galloprovincialis and expressions of many target genes in response to Cd stress.

MicroRNA transcriptome analysis of oriental river prawn Macrobrachium nipponense in responding to starvation stress

Food deprivation or fasting is an important environmental factor, and a regular occurrence in both natural aquatic habitats and artificial ponds. However, the potential immunoregulatory mechanisms underlying starvation stress in crustaceans remain unclear. MicroRNAs (miRNAs) are a new class of non-coding RNAs that can regulate various biological processes, such as stress and immune responses. In the present work, miRNAs related to starvation stress responses and immune properties were identified and characterised in oriental river prawn Macrobrachium nipponense using high-throughput sequencing and bioinformatics analyses. Twelve small RNA libraries from hepatopancreas tissue were sequenced across four fasting stages lasting 0, 7, 14 or 21 days. In total, 550 miRNAs were identified including 198 putative novel miRNAs and 352 conserved miRNAs belonging to 57 families. Moreover, compared with expression levels at 0 days, 27, 27 and 43 miRNAs were differentially expressed (DE-miRNAs) at 7, 14 and 21 days, respectively. Among these, four DE-miRNAs (ame-miR-190-5p, dme-miR-307a-3p, hme-miR-2788-3p and novel_68) were co-expressed at all three timepoints. Furthermore, 661 target genes regulated by these DE-miRNAs were identified, and associated functional annotations were derived by GO enrichment and KEGG pathway analyses, which showed that most DE-miRNAs were mainly participated in metabolic processes and immune responses. Furthermore, 26 host DE-miRNAs potentially participated in interactions with white spot syndrome virus (WSSV) were identified by predicting and analysing target genes from WSSV. The further WSSV challenge under starvation stress showed that dme-miR-307a-3p played a part in the antiviral responses against WSSV. Our results demonstrate that dme-miR-307a-3p may play vital regulatory roles in responding to starvation stress and WSSV infection. The findings contribute new insight into the molecular mechanisms associated with immune responses to environmental stress in crustaceans.

Regulation of shrimp prophenoloxidase activating system by lva-miR-4850 during bacterial infection

MicroRNAs (miRNAs) suppress gene expression and regulate biological processes. Following small RNA sequencing, shrimp hemocytes miRNAs differentially expressed in response to acute hepatopancreatic necrosis disease (AHPND) caused by Vibrio parahaemolyticus (VP_AHPND) were discovered and some were confirmed by qRT-PCR. VP_AHPND-responsive miRNAs were predicted to target several genes in various immune pathways. Among them, lva-miR-4850 is of interest because its predicted target mRNAs are two important genes of the proPO system; proPO2 (PO2) and proPO activating factor 2 (PPAF2). The expression of lva-miR-4850 was significantly decreased after VP_AHPND infection, whereas those of the target mRNAs, PO2 and PPAF2, and PO activity were significantly upregulated. Introducing the lva-miR-4850 mimic into VP_AHPND-infected shrimps caused a reduction in the PO2 and PPAF2 transcript levels and the PO activity, but significantly increased the number of bacteria in the VP_AHPND targeted tissues. This result inferred that lva-miR-4850 plays a crucial role in regulating the proPO system via suppressing expression of PPAF2 and PO2. To fight against VP_AHPND infection, shrimp downregulated lva-miR-4850 expression resulted in proPO activation.

Parallel analysis of miRNAs and mRNAs suggests distinct regulatory networks in Crassostrea gigas infected by Ostreid herpesvirus 1

Background

Since 2008, the aquaculture production of Crassostrea gigas was heavily affected by mass mortalities associated to Ostreid herpesvirus 1 (OsHV-1) microvariants worldwide. Transcriptomic studies revealed the major antiviral pathways of the oyster immune response while other findings suggested that also small non-coding RNAs (sncRNA) such as microRNAs might act as key regulators of the oyster response against OsHV-1. To explore the explicit connection between small non-coding and protein-coding transcripts, we performed paired whole transcriptome analysis of sncRNA and messenger RNA (mRNA) in six oysters selected for different intensities of OsHV-1 infection.

Results

The mRNA profiles of the naturally infected oysters were mostly governed by the transcriptional activity of OsHV-1, with several differentially expressed genes mapping to the interferon, toll, apoptosis, and pro-PO pathways. In contrast, miRNA profiles suggested more complex regulatory mechanisms, with 15 differentially expressed miRNAs (DE-miRNA) pointing to a possible modulation of the host response during OsHV-1 infection. We predicted 68 interactions between DE-miRNAs and oyster 3′-UTRs, but only few of them involved antiviral genes. The sncRNA reads assigned to OsHV-1 rather resembled mRNA degradation products, suggesting the absence of genuine viral miRNAs.

Conclusions

We provided data describing the miRNAome during OsHV-1 infection in C. gigas. This information can be used to understand the role of miRNAs in healthy and diseased oysters, to identify new targets for functional studies and, eventually to disentangle cause and effect relationships during viral infections in marine mollusks.

Deep sequencing of small RNAs reveals the repertoire of miRNAs and piRNAs in Biomphalaria glabrata

BACKGROUND

Biomphalaria glabrata snails are widely distributed in schistosomiasis endemic areas like America and Caribe, displaying high susceptibility to infection by Schistosoma mansoni. After the availability of B. glabrata genome and transcriptome data, studies focusing on genetic markers and small non-coding RNAs have become more relevant. The small RNAs have been considered important through their ability to finely regulate the gene expression in several organisms, thus controlling the functions like cell growth, metabolism, and susceptibility/resistance to infection.

OBJECTIVE

The present study aims on identification and characterisation of the repertoire of small non-coding RNAs in B. glabrata (Bgl-small RNAs).

METHODS

By using small RNA sequencing, bioinformatics tools and quantitative reverse transcription polymerase chain reaction (RT-qPCR), we identified, characterised, and validated the presence of small RNAs in B. glabrata.

FINDINGS

89 mature miRNAs were identified and five of them were classified as Mollusk-specific. When compared to model organisms, sequences of B. glabrata miRNAs showed a high degree of conservation. In addition, several target genes were predicted for all the mature miRNAs identified. Furthermore, piRNAs were identified in the genome of B. glabrata for the first time. The B. glabrata piRNAs showed strong conservation of uridine as first nucleotide at 5’ end, besides adenine at 10th position. Our results showed that B. glabrata has diverse repertoire of circulating ncRNAs, several which might be involved in mollusk susceptibility to infection, due to their potential roles in the regulation of S. mansoni development.

MAIN CONCLUSIONS

Further studies are necessary in order to confirm the role of the Bgl-small RNAs in the parasite/host relationship thus opening new perspectives on interference of small RNAs in the organism development and susceptibility to infection.

The sterol regulatory element binding protein homolog of Penaeus vannamei modulates fatty acid metabolism and immune response

The sterol regulatory element binding proteins (SREBPs) transcription factors family, which regulate the expression of genes involved in cellular lipid metabolism and homeostasis, have recently been implicated in various physiological and pathophysiological processes such as immune regulation and inflammation in vertebrates. Consistent with other invertebrates, we identified a single SREBP ortholog in Penaeus vannamei (designated PvSREBP) with transcripts ubiquitously expressed in tissues and induced by lipopolysaccharide (LPS), Vibrio parahaemolyticus and Streptococcus iniae. In vivo RNA interference (RNAi) of PvSREBP attenuated the expression of several fatty acid metabolism-related genes (i.e., cyclooxygenase (PvCOX), lipoxygenase (PvLOX), fatty acid binding protein (PvFABP) and fatty acid synthase (PvFASN)), which consequently decreased the levels of total polyunsaturated fatty acids (ΣPUFAs). In addition, PvSREBP silencing decreased transcript levels of several immune-related genes such as hemocyanin (PvHMC) and trypsin (PvTrypsin), as well as genes encoding for heat-shock proteins (i.e., PvHSP60, PvHSP70 and PvHSP90). Moreover, in silico analysis revealed the presence of SREBP binding motifs on the promoters of most of the dysregulated genes, while shrimp depleted of PvSREBP were more susceptible to V. parahaemolyticus infection. Collectively, we demonstrated the involvement of shrimp SREBP in fatty acids metabolism and immune response, and propose that PvSREBP and PvHMC modulate each other through a feedback mechanism to establish homeostasis. The current study is the first to show the dual role of SREBP in fatty acid metabolism and immune response in invertebrates and crustaceans.

MicroRNA and mRNA interactions coordinate the immune response in non-lethal heat stressed Litopenaeus vannamei against AHPND-causing Vibrio parahaemolyticus

While Vibrio parahaemolyticus (VP_AHPND) has been identified as the cause of early mortality syndrome (EMS) or acute hepatopancreatic necrosis disease (AHPND) in shrimp, mechanisms of host response remain unknown. Understanding these processes is important to improve farming practices because this understanding will help to develop methods to enhance shrimp immunity. Pre-treatment of shrimp with 5-minute chronic non-lethal heat stress (NLHS) for 7 days was found to significantly increase Litopenaeus vannamei survival against VP_AHPND infection. To elucidate the mechanism involved, mRNA and miRNA expression profiles from the hemocyte of L. vannamei challenged with VP_AHPND after NLHS with corresponding control conditions were determined by RNA-Seq. A total of 2,664 mRNAs and 41 miRNAs were differentially expressed after the NLHS treatment and VP_AHPND challenge. A miRNA-mRNA regulatory network of differentially expressed miRNAs (DEMs) and differentially expressed genes (DEGs) was subsequently constructed and the interactions of DEMs in regulating the NLHS-induced immune-related pathways were identified. Transcriptomic data revealed that miRNA and mRNA interactions contribute to the modulation of NLHS-induced immune responses, such as the prophenoloxidase-activating system, hemocyte homeostasis, and antimicrobial peptide production, and these responses enhance VP_AHPND resistance in L. vannamei.

Comparative analysis of shrimp (Penaeus vannamei) miRNAs expression profiles during WSSV infection under experimental conditions and in pond culture

In recent years, the importance of viral and host microRNAs (miRNAs) in mediating viral replication and control of host cellular machinery, has been realised and increasing efforts have been taken in order to understand the interactions of miRNAs from host and pathogen during infection. However, all existing studies has thus far been conducted in controlled experimental conditions and the veracity of these data for field conditions are yet to be established. In this framework, small RNA sequencing was performed to identify the miRNAs involved in shrimp (Penaeus vannamei) immune responses under two different WSSV infection conditions of natural infection and experimentally challenged conditions. The expression profiles of miRNAs of shrimp infected with WSSV under two contrasting conditions were compared and as a result, 23365 known miRNAs and 481 novel miRNAs were identified. Amongst the most abundantly expressed miRNAs, the hypoxia related miR-210 and immune pathway related miR-29b were expressed only in infected shrimps of both conditions. miR-8-5p, having a functional role in modulation of chitin biosynthesis was exclusively represented in higher numbers in the WSSV -infected shrimps under natural conditions whilst four of the miRNAs (mja-miR-6493-5p, mja-miR-6492, mmu-miR-3968, tcf-miR-9b-5p) identified from shrimps collected from pond culture targeted chitinase, an important enzyme involved in growth and moulting in shrimps, indicating an interaction between WSSV infection and moult cycle under culture conditions. Some of the miRNAs (tca-miR-87b-3p, cte-miR-277a) and miRNAs belonging to class miR-9, miR-981 that were identified only in WSSV infected shrimps under experimental conditions, are known to respond against WSSV infection in shrimps. Moreover, the miRNA target prediction revealed several immune-related gene targets such as cathepsin, c-type lectin, haemocyanin and ubiquitin protein ligase were commonly identified under both the conditions. However, the miRNAs identified from challenge experiment had wide number of gene targets as compared to the miRNAs of natural infection. The shrimp miRNA mja-miR-6489-3p, was also found to target early virus gene wsv001 of WSSV. Our study, therefore, provides the comparative analysis of miRNA expression from shrimp during WSSV infection in two different conditions.

miRNAs induced by white spot syndrome virus involve in immunity pathways in shrimp Litopenaeus vannamei

White shrimp Litopenaeus vannamei are widely cultured in the world and white spot syndrome virus (WSSV) led to huge economic losses in the shrimp industry every year. In the present study, miRNAs involved in the response of shrimp L. vannamei to WSSV infection were obtained through the Illumina HiSeq 2500 high-throughput next-generation sequencing technique. A total number of 7 known miRNAs and 54 putative novel miRNAs were obtained. Among them, 14 DEMs were identified in the shrimp infected with WSSV. The putative target genes of these DEMs were related to host immune response or signaling pathways, indicating the importance of miRNAs in shrimp against WSSV infection. The results will provide information for further research on shrimp response to virus infection and contribute to the development of new strategies for effective protection against WSSV infections.

High-throughput sequencing analysis of microRNAs in gills of red swamp crayfish, Procambarus clarkii infected with white spot syndrome virus

MicroRNAs (miRNAs) are important posttranscriptional regulators. They play an important role in the antiviral innate immunity of invertebrates. In the present study, high-throughput small RNAs Illumina sequencing systems were carried out to identify differentially expressed miRNAs (DEMs) in the gills of Procambarus clarkii, which was challenged with white spot syndrome virus (WSSV). Our results identified 11,617 known and 6 novel miRNAs in normal group (NG) and WSSV-challenged group (WG) small RNA libraries. Additionally, 27 DEMs were shown to participate in the antiviral innate immunity of P. clarkii and were significantly upregulated or downregulated. In addition, the results of the KEGG pathway prediction of the DEMs target genes showed that putative target genes of these 27 DEMs were related mainly to the RNA transport pathway, tight junction pathway, mRNA surveillance pathway, regulation actin cytoskeleton pathway, focal adhesion pathway, and MAPK signaling pathway. These results provide important information for future studies about the antiviral innate immunity of crustaceans.

Differential expression of microRNAs in Portunus trituberculatus in response to Hematodinium parasites

Latest studies have indicated that microRNAs (miRNAs) play important roles in defending against bacterial and viral infections in marine crustacean, whereas little is known regarding the immunological roles of crustacean miRNAs in response to parasitic infection. To further reveal the host-parasite interactions between the parasitic dinoflagellate Hematodinium and its crustacean hosts, we applied the high-throughput sequencing technology to identify and characterize miRNAs in the Chinese swimming crab Portunus trituberculatus challenged with the Hematodinium parasite at a timescale of 16 days (d). A total of 168 miRNAs were identified and 51 miRNAs were differentially expressed in the hepatopancreas tissues of affected hosts. Eleven of the differentially expressed miRNAs were selected and verified by the quantitative real-time RT-PCR (qRT-PCR), manifesting the consistency between the high throughout sequencing and qRT-PCR assays. Further analysis of the putative target genes indicated that various immune-related pathways (e.g. endocytosis, Fc gamma R-mediated phagocytosis, lysosome, ECM-receptor interaction, complement and coagulation cascades, antigen processing and presentation, focal adhesion, etc.) and signal transduction pathways (e.g. JAK-STAT signaling pathway, MAPK signaling pathway, p53 signaling pathway, etc.) were mediated by the differentially expressed miRNAs. The results presented fundamental knowledge on the immunological roles of crustacean miRNAs and contributed to the better understanding of hosts' miRNAs-mediated immunity against the parasitic infection.

White Spot Syndrome Virus-Induced Shrimp miR-315 Attenuates Prophenoloxidase Activation via PPAE3 Gene Suppression

MicroRNAs (miRNAs), the small non-coding RNAs, play a pivotal role in post-transcriptional gene regulation in various cellular processes. However, the miRNA function in shrimp antiviral response is not clearly understood. This research aims to uncover the function of pmo-miR-315, a white spot syndrome virus (WSSV)-responsive miRNAs identified from Penaeus monodon hemocytes during WSSV infection. The expression of the predicted pmo-miR-315 target mRNA, a novel PmPPAE gene called PmPPAE3, was negatively correlated with that of the pmo-miR-315. Furthermore, the luciferase assay indicated that the pmo-miR-315 directly interacted with the target site in PmPPAE3 suggesting the regulatory role of pmo-miR-315 on PmPPAE3 gene expression. Introducing the pmo-miR-315 into the WSSV-infected shrimp caused the reduction of the PmPPAE3 transcript level and, hence, the PO activity activated by the PmPPAE3 whereas the WSSV copy number in the shrimp hemocytes was increased. Taken together, our findings state a crucial role of pmo-miR-315 in attenuating proPO activation via PPAE3 gene suppression and facilitating the WSSV propagation in shrimp WSSV infection.

Identification of MicroRNAs and Their Target Genes Associated with Ovarian Development in Black Tiger Shrimp (Penaeus monodon) Using High-Throughput Sequencing

Plenty of evidence showing that microRNAs (miRNAs) post-transcriptionally regulate gene expression and are involved in a wide range of biological processes. However, the roles of miRNAs in ovarian development process remain largely unknown in shrimp. In the present study, high-throughput sequencing of small RNAs was performed to find specific miRNAs that are involved in ovarian development process in Penaeus monodon. Two small RNA libraries were constructed from undeveloped (UNDEV group) and developed (DEV group) ovarian tissues in P. monodon. In total, 43 differentially expressed miRNAs were identified between the two groups (P ≤ 0.05, |log2 ratio| ≥1), and their expression profiles were validated by qRT-PCR. In order to further clarify the functional roles of these differentially expressed miRNAs during ovarian development process, target gene prediction was performed. In total, 4,102 target genes of 43 miRNAs were predicted, then clustered by the Kyoto Encyclopedia of Genes and Genomes (KEGG) database; only four specific pathways related to ovarian development were obtained (P < 0.05). Dual-luciferase reporter assays and integrated expression analysis were also conducted to further clarify the interaction between the miRNAs and their target mRNAs. This study provides important information about the function of miRNAs involved in ovarian developmental stages in P. monodon.

Eriocheir sinensis microRNA-7 targets crab Myd88 to enhance white spot syndrome virus replication

MicroRNAs (miRNAs) are non-coding RNAs that regulate gene expression at the posttranscriptional level. In this study, the function of microRNA-7 (miR-7) in host-virus interaction was investigated. Replication of White spot syndrome virus (WSSV) was enhanced with the overexpression of miR-7 and inhibited with the downregulation of miR-7 by using anti-miRNA oligonucleotide AMO-miR-7. The target gene of miR-7 was predicted using bioinformatics methods. Results showed that crab myeloid differentiation factor 88 (Myd88) could be targeted by miR-7. When the expression of Myd88 was knocked down by sequence-specific siRNA, WSSV copies in crabs were significantly increased. Further findings revealed that knockdown of Myd88, Tube, or Pelle inhibited the expressions of interleukin enhancer-binding factor 2 homolog (ILF2) and interleukin-16-like gene (IL-16L). While ILF2 was silenced, IL-16L expression was inhibited. The overexpression of miR-7 inhibited the expressions of ILF2 and IL-16L. Moreover, when ILF2 or IL-16L was silenced, WSSV copies in crabs were increased. Thus, the upregulated expression of miR-7 during WSSV challenge suppressed the host Myd88-ILF2-(IL-16L) signaling pathway in crabs and enhanced WSSV replication. Our study indicated that WSSV utilized crab miR-7 to enhance virus replication during infection.

Differential expression of microRNAs in hemocytes from white shrimp Litopenaeus vannamei under copper stress

MicroRNAs (miRNAs) are small noncoding RNAs that regulate diverse cellular processes, including organismal stress response, through posttranscriptional repression of gene transcripts. They are known to have antiviral functions in aquatic crustacean species, but little is known about the role of miRNAs against environmental stress caused by Cu, a common chemical contaminant in aquatic environment. We performed small RNA sequencing to characterize the differentially expressed microRNAs in Cu exposed shrimp. A total of 4524 known miRNAs and 73 novel miRNAs were significantly (P < .05) differentially expressed after Cu exposure. The peak size of miRNAs was 22 nt. Among them, 218 miRNAs were conserved across 115 species. The validation of 12 miRNAs by stem-loop quantitative RT-PCR were found to be coherent with the expression profile of deep sequencing data as evaluated with Pearson's correlation coefficient (r = 0.707). Target genes of these differentially expressed miRNAs related to immune defense, apoptosis, and xenobiotics metabolism also showed significant changes in expression under Cu stress. The present study provides the first characterization of L. vannamei miRNAs and some target genes expression in response to Cu stress, and the findings support the hypothesis that certain miRNAs along with their target genes might be essential in the intricate adaptive response regulation networks. Our current study will provide valuable information to take an insight into molecular mechanism of L. vannamei against environmental stress.

Identification and characterization of intestine microRNAs and targets in red swamp crayfish, Procambarus clarkii infected with white spot syndrome virus

MicroRNAs (miRNAs) are small non-coding endogenous RNA molecules that play important roles in the innate immunity system of invertebrates, especially in the aspect of antivirus. In the present study, high-throughput small RNA Illumina sequencing systems were used to identify differentially expressed miRNAs (DEMs) from the intestines of Procambarus clarkii that were infected with white spot syndrome virus (WSSV). As a result, 39 known and 12 novel miRNAs were identified in both NG and WG small RNA libraries. Seven DEMs were determined to be involved in the antiviral innate immunity in the intestines of P. clarkii. The results of the target gene predictions of the DEMs showed that the putative target genes of these 7 DEMs are related to tight junctions, vascular smooth muscle contraction regulation of the actin cytoskeleton, focal adhesion, RNA transport, mRNA surveillance, viral carcinogenesis, and Salmonella infection. These results provide theoretical insights for future studies on the antiviral immunity of crustaceans.

Identification and characterization of lymph organ microRNAs in red swamp crayfish, Procambarus clarkii infected with white spot syndrome virus

MicroRNAs (miRNAs) were important post-transcriptional regulators and played vital roles in innate immunity system of invertebrates, especially in the aspect of antivirus. In this study, using high-throughput small RNAs Illumina sequencing system, differentially expressed miRNAs (DEMs) from lymph organs in red swamp crayfish, Procambarus clarkii, infected with white spot syndrome virus, were identified. As a result, 32 known miRNAs and 7 novel miRNAs were identified in crayfish lymph organ small RNAs library of NG and WG. Among them, 7 differentially expressed miRNAs (DEMs) were predicted to be involved in the lymph organ antiviral innate immunity of P. clarkii. Besides, the results showed that putative target genes of these DEMs were related with tight junction, RNA transport, regulation of actin cytoskeleton, focal adhesion, vascular smooth muscle contraction, mRNA surveillance pathway, NOD-like receptor signaling pathway, leukocyte transendothelial migration, and protein processing in endoplasmic reticulum. These results might provide the guiding theoretical foundation for future studies about crustaceans' antiviral innate immunity.

The identification of microRNAs involved in the response of Chinese shrimp Fenneropenaeus chinensis to white spot syndrome virus infection

MicroRNA (miRNA) is a class of small noncoding RNA, which is involved in the post-transcriptional regulation in all metazoan eukaryotes. MiRNAs might play an important role in the host response to virus infection. However, miRNAs in the aquatic crustacean species were not extensively investigated. To obtain a better understanding of the response of Chinese shrimp Fenneropenaeus chinensis to white spot syndrome virus (WSSV) infection, the sequence and expression profile of miRNAs in the hepatopancreas of WSSV-infected F. chinensis were obtained by the high-throughput Illumina HiSeq 2500 deep sequencing technique. A total number of 129 known miRNAs and 44 putative novel miRNAs were identified from the deep sequencing data. The peak size of miRNAs was 22 nt (37.0%). 25 miRNAs were significantly (P < 0.05) differentially expressed post WSSV infection. Six of the differentially expressed miRNAs were randomly selected for further verification by the real-time RT-PCR technique. The results showed that there was a consistency between the deep sequencing and real-time RT-PCR assay. The target genes of differentially expressed miRNAs were predicted. Each miRNA had 4 target genes on average. The results suggested that some specific miRNAs might be involved in the response of F. chinensis to WSSV infection, and further provided basic information for the investigation of specific miRNAs in F. chinensis.

Characterization of microRNAs by deep sequencing in red claw crayfish Cherax quadricarinatus haematopoietic tissue cells after white spot syndrome virus infection

White spot syndrome virus (WSSV) is one of the most prevalent and widespread viruses in both shrimp and crayfish aquaculture. MicroRNAs (miRNAs) are crucial post-transcriptional regulators and play critical roles in cell differentiation and proliferation, apoptosis, signal transduction and immunity. In this study, miRNA expression profiles were identified via deep sequencing in red claw crayfish Cherax quadricarinatus haematopoietic tissue (Hpt) cell cultures infected with WSSV at both early (i.e., 1 hpi) and late (i.e., 12 hpi) infection stages. The results showed that 2 known miRNAs, namely, miR-7 and miR-184 play key roles in immunity. Meanwhile, 106 novel miRNA candidates were predicted by software in these combined miRNA transcriptomes. Compared with two control groups, 36 miRNAs showed significantly different expression levels after WSSV challenge. Furthermore, 10 differentially expressed miRNAs in WSSV-exposed Hpt cells were randomly selected for expression analysis by quantitative real-time RT-PCR. Consistent with the expression profiles identified by deep sequencing, RT-PCR showed a significant increase or decrease in miRNA expression in Hpt cells after WSSV infection. Prediction of targets of miRNAs such as miR-7, cqu-miR-52, cqu-miR-126 and cqu-miR-141 revealed that their target genes have diverse biological roles, including not only immunity but also transcriptional regulation, energy metabolism, cell communication, cell differentiation, cell death, autophagy, endocytosis and apoptosis. These results provide insight into the molecular mechanism of WSSV infection and highlight the function of miRNAs in the regulation of the immune response against WSSV infection in crustaceans.

Oral transfer of chemical cues, growth proteins and hormones in social insects

Social insects frequently engage in oral fluid exchange - trophallaxis - between adults, and between adults and larvae. Although trophallaxis is widely considered a food-sharing mechanism, we hypothesized that endogenous components of this fluid might underlie a novel means of chemical communication between colony members. Through protein and small-molecule mass spectrometry and RNA sequencing, we found that trophallactic fluid in the ant Camponotus floridanus contains a set of specific digestion- and non-digestion related proteins, as well as hydrocarbons, microRNAs, and a key developmental regulator, juvenile hormone. When C. floridanus workers' food was supplemented with this hormone, the larvae they reared via trophallaxis were twice as likely to complete metamorphosis and became larger workers. Comparison of trophallactic fluid proteins across social insect species revealed that many are regulators of growth, development and behavioral maturation. These results suggest that trophallaxis plays previously unsuspected roles in communication and enables communal control of colony phenotypes.

Differential expression of microRNAs of Litopenaeus vannamei in response to different virulence WSSV infection

WSSV is one of the most harmful pathogeny in the pacific white shrimp, and genetic variations caused the strains of different virulence. MicroRNAs (miRNAs) involved in the regulation of virus defense. To understand the different virulence of WSSV on miRNA expression in Litopeneaus vannamei, the deep sequencing was performed to compare two small RNA libraries prepared from hepatopancreas of Litopeneaus vannamei infected with normal-virulence or low-virulence WSSV. Approximately 29,398,623 raw reads from normal-virulence library and 35,291,803 raw reads from low-virulence library were obtained. There were about 37 miRNAs homologs identified. Sixteen miRNAs were significantly up-regulated and twenty-one miRNAs were significantly down-regulated in normal-virulence infection library compared with low-virulence infection library. Of these, Igi-miR-1175-3p was the most significant different miRNA, followed by bmo-miR-1175-3p and ipu-miR-26b, respectively. The putative target genes for differentially expressed miRNAs were concerned with biological processes, signal meditated, cell differentiation and apoptosis, immune recognition and other more functions. The results will help to understand the miRNAs response to different virulence WSSV infection.

The Dorsal/miR-1959/Cactus feedback loop facilitates the infection of WSSV in Litopenaeus vannamei

miR-1959, a novel microRNA identified from Litopenaeus vannamei, mediates a positive feedback loop between Dorsal and Cactus that can continuously maintain the activation of the NF-κB pathway. It has been known that miR-1959 is involved in antibacterial immunity in shrimp, but its function in antiviral responses is still unknown. In this study, we focused on the role of miR-1959 in infection of white spot syndrome virus (WSSV), the major viral pathogen in shrimp worldwide. The expression of miR-1959 in shrimp hemocytes, gill, and hepatopancreas was significantly up-regulated upon WSSV infection. Dual-luciferase reporter assays demonstrated that miR-1959 could enhance the activity of the promoter of WSSV immediate early gene ie1. In vivo experiments also showed that inhibition of miR-1959 led to decrease of the mortality of WSSV-infected shrimp and the genome copies of WSSV in tissues, meanwhile the expression of WSSV ie1 and VP28 genes was down-regulated. In contrast, increase of the miR-1959 level in shrimp by injection of miR-1959 mimics produced opposite results. These suggested that the Dorsal/miR-1959/Cactus feedback loop could favor the infection of WSSV in shrimp. Thus, our study helps further reveal the interaction between WSSV and shrimp immune system.