Hemocyte Production Research Articles

Comparison analysis of circulating hemocytes in decapod crustaceans

Hemocytes are the primary immune cells of crustaceans. Few comparison studies have been done among different crustaceans and some key parameters of circulating hemocytes have not been investigated. Here, we compared the circulating hemocytes in six decapod crustaceans, Cherax quadrinatus, Procambarus clarkii, Penaeus vannamei, Penaeus monodon, Eriocheir sinensis, and Scylla paramamosain. Although the hemocytes of different species vary in size, they share common morphological characteristics. Based on their morphological features, circulating hemocytes can be basically classified into granular cells (GCs), semi-granular cells (SGCs), and hyaline cells (HCs). In the six decapods analyzed in this study, the proportion of GCs varied from 10 % to 30 %. P. vannamei, P. monodon, and P. clarkii had fewer GCs in circulation than the other three species. Correspondingly, proliferation was detected only in a small portion of cells in P. vannamei, P. monodon, and P. clarkii under physical conditions. The hemocyte renewal rates for P. clarkii, E. sinensis, and C. quadrinatus were 6.1 %, 5.1 %, and 1.5 % per day, while no steady new hemocyte production was found in S. paramamosain within six days. These data give a general picture of the similarities and differences of circulating hemocytes in decapods and provide a base for an in-depth study of their immune system.

Dragon fruit-derived oligosaccharides alter hemocyte-mediated immunity and expression of genes related to innate immunity and oxidative stress in Daphnia magna

Dragon fruit oligosaccharide (DFO) is an indigestible prebiotic that enhances the growth and reproduction of Daphnia magna, increases the expression of genes involved in immunity, and reduces oxidative stress. This study investigated the effects of DFO on the expression of innate immunity- (Toll, Pelle, proPO, A2M, and CTL), oxidative stress- (Mn-SOD), and nitric oxide (NO) synthesis-related genes (NOS1, NOS2, and arginase) as well as NO localization and number of hemocytes in D. magna. For this ten-day-old D. magna were treated with 0 or 9 mg l−1 of DFO for 24 and 85 h. Gene expression levels, NO intensity and localization, and total hemocytes were evaluated. After 24 h, the expression of Toll and proPO increased significantly (p < 0.05), while that of C-type lectins (CTL) was reduced (p < 0.05). At 85 h, Mn-SOD and CTL expressions were markedly suppressed (p < 0.05). NO was mostly localized in the foregut, midgut, hindgut, and carapace. The expression of NOS1 was reduced after 24 h (p < 0.05). In addition, NO intensity at 24 h was insignificantly lower than the control (p > 0.05). At 85 h, the expression of NOS1, NOS2, and arginase was higher than control, but NO intensity did not differ significantly (p > 0.05). Furthermore, the total hemocyte count elevated remarkably at 85 h (p < 0.05). Our study suggested that 9 mg l−1 of DFO could alter the expression of the genes related to innate immunity, oxidative stress, and NO synthesis in D. magna and significantly stimulate hemocyte production.

NO production of granulocytes associated with antibacterial immune response in Tegillarca granosa

Nitric oxide (NO) is a signaling molecule and immune effector produced by the nitric oxide synthases (NOS), which involved to various physiological processes of animals. In marine bivalves, hemocytes play important roles in antimicrobial innate immune response. Although hemocyte-derived NO has been detected in several bivalves, the immune function of hemocyte-derived NO is not well understood. Here, we investigated the antibacterial response of hemocyte-derived NO in the blood clam Tegillarca granosa. Two types of hemocytes including erythrocytes and granulocytes were isolated by Percoll density gradient centrifugation, their NO production and TgNOS expression level were analyzed. The results showed that NO was mainly produced in granulocytes and almost no detected in erythrocytes. The granulocytes showed significantly higher NO level and TgNOS expression level than the erythrocytes. And the TgNOS expression level was significantly increased in granulocytes after Vibro parahemolyticus challenge. In addition, the NO donor sodium nitroprusside (SNP) significantly increased the NO production of hemocytes to kill pathogenic bacteria. In summary, the results revealed that granulocytes-derived NO play vital roles in the antimicrobial immune response of the blood clam.

Viability Analysis of Biomphalaria glabrata Hemocytes During Schistosoma mansoni Infection And Glyphosate-Based Herbicide Exposure

Pesticides are chemical agents that have a range of harmful effects on human health and the environment. They can cause drastic changes in natural communities, such as macroinvertebrates, plankton and fish. Snails, including Biomphalaria glabrata, are often present in aquatic communities and have multiple roles in limnic ecosystems. B. glabrata is an intermediate host of several species of helminths of medical and veterinary importance, such as Schistosoma mansoni, the etiological agent of schistosomiasis. The original Roundup® herbicide can affect snails and directly affects S. mansoni hemocytes, cells that act in the snails’ immune defense. Here we analyzed the effect of herbicide exposure on B. glabrata hemocytes divided into four groups: control group, infected-only group, treated-only group and infected+treated group. For this, flow cytometry and Neubauer-chamber counting were used to determine the morphology, viability and lectin expression profiles of hemocytes. We observed that the group infected by S. mansoni and treated with herbicide had a higher concentration of dead hemocytes in relation to the other groups. The treated group showed similar results to the control group, suggesting that the herbicide (Roundup™) alone does not interfere with the snails’ immune system. Regarding cellular-morphological-characterization analysis, hyalinocytes were the cells most commonly found in all groups studied. These findings suggest that S. mansoni infection and exposure to pesticides directly the immune system of the snails, stimulating the production of hemocytes, especially hyalinocytes, which have a high phagocytic power to quell the infection, but with toxic effects on the snail.

Transgenerational plasticity in a zooplankton in response to elevated temperature and parasitism.

Organisms are increasingly facing multiple stressors, which can simultaneously interact to cause unpredictable impacts compared with a single stressor alone. Recent evidence suggests that phenotypic plasticity can allow for rapid responses to altered environments, including biotic and abiotic stressors, both within a generation and across generations (transgenerational plasticity). Parents can potentially "prime" their offspring to better cope with similar stressors or, alternatively, might produce offspring that are less fit because of energetic constraints. At present, it remains unclear exactly how biotic and abiotic stressors jointly mediate the responses of transgenerational plasticity and whether this plasticity is adaptive. Here, we test the effects of biotic and abiotic environmental changes on within- and transgenerational plasticity using a Daphnia-Metschnikowia zooplankton-fungal parasite system. By exposing parents and their offspring consecutively to the single and combined effects of elevated temperature and parasite infection, we showed that transgenerational plasticity induced by temperature and parasite stress influenced host fecundity and lifespan; offsprings of mothers who were exposed to one of the stressors were better able to tolerate elevated temperature, compared with the offspring of mothers who were exposed to neither or both stressors. Yet, the negative effects caused by parasite infection were much stronger, and this greater reduction in host fitness was not mitigated by transgenerational plasticity. We also showed that elevated temperature led to a lower average immune response, and that the relationship between immune response and lifetime fecundity reversed under elevated temperature: the daughters of exposed mothers showed decreased fecundity with increased hemocyte production at ambient temperature but the opposite relationship at elevated temperature. Together, our results highlight the need to address questions at the interface of multiple stressors and transgenerational plasticity and the importance of considering multiple fitness-associated traits when evaluating the adaptive value of transgenerational plasticity under changing environments.

ROS-directed activation of Toll/NF-κB in the hematopoietic niche triggers benzene-induced emergency hematopoiesis.

Hematopoietic stem cells/progenitor cells (HSC/HPCs) orchestrate the hematopoietic process, effectively regulated by the hematopoietic niche under normal and stressed conditions. The hematopoietic niche provides various soluble factors which influence the differentiation and self-renewal of HSC/HSPs. Unceasing differentiation/proliferation/high metabolic activity of HSC/HPCs makes them susceptible to damage by environmental toxicants like benzene. Oxidative stress, epigenetic modifications, and DNA damage in the HSC/HPCs are the key factors of benzene-induced hematopoietic injury. However, the role of the hematopoietic niche in benzene-induced hematopoietic injury/response is still void. Therefore, the current study aims to unravel the role of the hematopoietic niche in benzene-induced hematotoxicity using a genetically tractable model, Drosophila melanogaster. The lymph gland is a dedicated hematopoietic organ in Drosophila larvae. A group of 30-45cells called the posterior signaling center (PSC) in the lymph gland acts as a niche that regulates Drosophila HSC/HPCs maintenance. Benzene exposure to Drosophila larvae (48h) resulted in aberrant hemocyte production, especially hyper-differentiation of lamellocytes followed by premature lymph gland dispersal and reduced adult emergence upon developmental exposure. Subsequent genetic experiments revealed that benzene-induced lamellocyte production and premature lymph gland dispersal were PSC mediated. The genetic experiments further showed that benzene generates Dual oxidase (Duox)-dependent Reactive Oxygen Species (ROS) in the PSC, activating Toll/NF-κB signaling, which is essential for the aberrant hemocyte production, lymph gland dispersal, and larval survival. Together, the study establishes a functional perspective of the hematopoietic niche in a benzene-induced hematopoietic emergency in a genetic model, Drosophila, which might be relevant to higher organisms.

Effect of low-frequency noise on the survival rate and immunity of infected Vibrio parahaemolyticus sea slug (Onchidium reevesii)

Anthropogenic noise in the marine environment has become a global environmental pollutant that affects the behavior, physiology and immunity of marine animals. However, the resistance of marine animals to pathogens while under the influence of noise is a topic that has received little attention. To assess the immune defense response of sea slugs against pathogens when exposed to low frequency noise, we performed 120 h exposure experiments on sea slugs after a Vibrio parahaemolyticus application in low frequency noise at 500 Hz and 1000 Hz. We found that after the infection with V. parahaemolyticus, the survival rate of the sea slugs decreased, the apoptosis rate and reactive oxygen species (ROS) production of hemocytes increased significantly (P < 0.05), the proliferation of hemocytes accelerated, the activities of enzymes such as superoxide dismutase (SOD), catalase (CAT), alkaline phosphatase (AKP), alanine transaminase (ALT) and lysozyme (LZM) in the hepatopancreas increased significantly, and the expression of TNF signaling pathway-related genes (TNF-α, FADD, Caspase 8, Caspase 3) and Hsp70 genes were generally upregulated. In addition, exposure of sea slug after infected with V. parahaemolyticus to low frequency noise resulted in a significant increase in both antioxidant and immune parameters, which were positively correlated with frequency. The results showed that noise frequency and exposure time had an interactive effect on the above indicators. In summary, low-frequency noise exposure increases the risk of pathogenic infections in sea slugs and exacerbates the negative effects on the antioxidant capacity and immune metabolism of the organism.

A novel Ush transcription factor involving in hematopoiesis of Eriocheir sinensis.

The FOG transcriptional factor is a co-regulator that recognizes and binds to the GATA N-terminal zinc-finger domain and participates in hemocyte production and differentiation. In this study, an FOG-like gene, Ush, was characterized from Eriocheir sinensis, which consists of an 897bp full-length open reading frame, encoding a polypeptide of 298 amino acids with four ZnF_C2H2 domains. The EsUsh mRNA transcripts were mainly expressed in the hematopoietic tissue (HPT) and hemocytes, and were significantly higher in hyalinocytes than semi-granulocytes and granulocytes, which were separated by Percoll gradient centrifugation. The transcription levels of EsUsh were found to be significantly upregulated in HPT, but downregulated in hemocytes after exsanguination. By using flow cytometry to determine the percentage of hemocyte sub-population after exsanguination, the percentage of hyalinocytes was found to significantly downregulated, while the percentage of granulocytes was significantly upregulated. Silencing EsUsh by dsRNA interference significantly decreased the percentage of hyalinocytes and small granulocytes, and increased the percentage of medium granulocytes and large granulocytes. Such findings suggest that EsUsh might be involved in hemocyte production and differentiation, especially in promoting hyalinocyte formation and limiting granulocyte generation and differentiation.

Ecological aspects of bivalve adaptation to salinity fluctuations on the example of Anadara Kagoshimensis

Impact of salinity stress on the ark clam (Anadara kagoshimensis (Tokunaga, 1906)) hemocyte functions were investigated using flow cytometry and light scattering technique. In control group water salinity was 18 ppm and experimental groups were carried at 14 ppm, 8 ppm, 35 ppm and 45 ppm. Hemolymph osmolarity decreased at hypoosmotic conditions and increased after hyperosmotic treatment. Osmotic stress induced changes in osmotic fragility of the ark clam hemocytes. Salinity 14 ppm did not affect the functional parameters of hemocytes. Incubation of ark clams at salinity and 35 ppm did not influence on the mitochondrial membrane potential of hemocytes but led to a decrease in hemocyte reactive oxygen species (ROS) production by 30 % compared to control. An increase in water salinity to 45 ppm and its decrease to 8 ppm induced substantial changes in the ROS production and mitochondrial membrane potential of hemocytes. Hyposalinity (8 ppm) led to an increase in ROS production by hemocytes (up to 2.4 times) and mitochondrial membrane potential (up to 1.3 times). An increase of salinity level from 18 ppm to 45 ppm decreased the total ability of hemocytes to produce ROS by 11% and increased mitochondrial potential of hemocytes by 150%.

Survival capacity of the common woodlouse Armadillidium vulgare is improved with a second infection of Salmonella enterica

Immune priming has been widely observed in invertebrates. However, this phenomenon remains incompletely characterized concerning the time course of the protective effect and immune responses. Here, we investigated the existence of a protective effect in the terrestrial isopod Armadillidium vulgare against a second infection with the bacterium Salmonella enterica. We primed animals with a low dose of living bacteria or with the bacterial culture medium. One day, 7 or 15 days later, we measured haemocytes concentration and viability and we injected a LD50 of living S. enterica to monitor the survival rates of infected individuals. We show that A. vulgare is better protected (i.e. survival improvement) upon secondary infection when it has encountered S. enterica 7 days before. This protection, which tends to persist 15 days after the first infection, is however not observed when the priming is performed only 1 day before the LD50 injection. Besides providing a new invertebrate example, we highlight this protection is dynamic and may be partly due to a high haemocyte production.

Directed differentiation of granular cells from crayfish hematopoietic tissue cells

Hemocytes are the major immune cells of crustaceans. New hemocyte production is required throughout the life cycle of these animals to maintain a functional immune system. The mechanism of crustacean hematopoiesis has just begun to be understood and new methods are needed for the investigation of this process. Here we report the directed differentiation of granular cells (GCs) from the hematopoietic tissue (HPT) cells of Cherax quadricarinatus in vitro. We started by providing the cultured HPT cells with different additives to induce possible differentiation. We found that crayfish muscle extract greatly promoted the physical status of the cells and induced the formation of refractile cytoplasmic granules. The transcription of marker genes and the production of functional prophenoloxidase further confirmed the formation of mature GCs. In our experiments, young GCs usually started to develop in ∼2 weeks post induction and over 60% of the cells became mature within 3–4 weeks. This is the first time that the fully differentiation of crustacean hemocytes is accomplished in vitro. It provides a powerful tool for in-depth study of crustacean hematopoiesis.

The impact of ocean acidification and cadmium on the immune responses of Pacific oyster, Crassostrea gigas

Seawater acidification (OA) and cadmium (Cd) has the potential to lead to immunosuppression effect on marine bivalves. However, the interaction between these two environmental stressors on immune system of marine bivalves has received limited attention. In order to evaluate the defense responses of oysters under the combined exposure to OA and cadmium, the oysters Crassostrea gigas were exposed to 10 μg/L Cd at three pH levels (8.1, 7.8 and 7.6) for 31 days. Results showed that OA exposure alone led to increased DNA damage, apoptosis rate and ROS production of hemocytes. However, inhibited phagocytosis rate, combined with increased DNA damage, apoptosis rate and ROS production of hemocytes were observed in oysters under exposure to Cd exposure alone or combined with OA. Significant interactive effects between OA and Cd were observed on ROS production and DNA damage of hemocytes. In addition, there is generally significant increase in the mRNA expression of genes related to immune-related TLR pathway and two immune factors (TNF and integrin beta-1B) in Cd-exposed oysters at pH 7.6. The results revealed that even though the mRNA expression of genes related to immune responses (TLR pathway and immune factors) was stimulated to counteract the immunosuppression caused by acidified seawater and Cd, depressed hemocyte function perhaps sensitized oysters to potential pathogen infection.

A Prokineticin (PK)-like cytokine from Chinese mitten crab Eriocheir sinensis promotes the production of hemocytes via reactive oxygen species

Astakine is a cytokine-like factor containing a prokineticin domain, which directly participates in hematopoiesis and blood cell differentiation. In the present study, a novel Astakine gene was identified from Chinese mitten crab Eriocheir sinensis (designated as EsAst). The full-length cDNA of EsAst was of 1163 bp, consisting of a 5′ untranslated region (UTR) of 120 bp, a 3′ UTR of 656 bp, and an open reading frame (ORF) of 387 bp encoding a polypeptide of 128 amino acids. There were a signal peptide and a prokineticin domain with nine conserved cysteine residues in the deduced amino acid sequence of EsAst. EsAst shared higher similarity with Astakines from Penaeus monodon and Pacifastacus leniusculus, and it was closely clustered with the Astakine from shrimp P. monodon in the phylogenetic tree. The EsAst mRNA transcript was higher expressed in hemocytes and hepatopancreas. The relative expression level of EsAst in hemocytes was continuously increased from 1.5 to 48 h after Vibro anguillarum challenge compared that in the untreated control group. After Pichia pastoris GS115 challenge, the relative expression level of EsAst in hemocytes was also up-regulated. After rEsAst injection, ROS levels in HPT cells were also increased at 12 and 24 h, and the total hemocyte counts were also significantly increased at 6, 9, 12, and 24 h post rEsAst injection. The interference of EsAst expression with dsRNA injection could delay the recovery of hemocytes production post A. hydrophila stimulation. When mitochondrial complexes I was knock down by dsRNA, ROS levels were decreased and THCs were also decreased. Recovery of hemocyte production inducing by A. hydrophila stimulation and rEsAst injection were delayed with dsEsbc1 injection. When ROS levels were increased after RNAi of Lon protease, THCs were also increased. The expression levels of five genes (EsJNK, EsSTAT, EsPI3K, EsAKT1, EsP70S6K) involved in SAPK-JNK and mTOR signaling pathways were up-regulated at 12 and 24 h in rEsAst group and EsLon dsRNA group compared with that in EGFP dsRNA group, and were similar to the trend of ROS levels. These results collectively suggested that EsAst should be a novel Astakine to promote the production of hemocytes in a ROS-dependent way in E. sinensis.

The ancient role for GATA2/3 transcription factor homolog in the hemocyte production of oyster

Hemocytes, the cellular component of invertebrate hemolymph, are essential for invertebrate immunity, but the hematopoiesis and regulation mechanism are still largely unknown. In the present study, a conserved hematopoietic transcription factor Cg-GATA2/3 was identified in Pacific oyster Crassotrea gigas, which was evolutionarily close to the vertebrate GATA1/2/3. Cg-GATA2/3 was mainly distributed in the immune organs, such as gill, hemocytes, and mantle. After Cg-GATA2/3 was interferenced by dsRNA, the mRNA expressions of hemocytes specific gene (EcSOD) and hematopoietic transcription factor (C-Myb) were all significant down-regulated, and the hemocyte renewal rates also decreased both in hemolymph and gill. During the larval developmental stages, the mRNA transcripts of Cg-GATA2/3 increased immediately after fertilization and kept a high level during blastula and early trochophore larvae stage (4-10 hpf, hours post fertilization), then decreased sharply in early D-veliger larvae stage (15 hpf). Whole-mount immunofluorescence assay further revealed that the abundant immunoreactivity of Cg-GATA2/3 was distributed in the whole body of blastula and gastrula embryos, while specialized gradually to a ring structure around the dorsal region in trochophore larvae. In the D-veliger and umbo larvae, scattered positive signals appeared in the specific sinus structure on the dorsal side and velum region. These results demonstrated that Cg-GATA2/3 was a hematopoietic lineage-specific transcription factor to regulate the hemocyte production, and it could also be used as hematopoietic specific marker to trace potential developmental events of hematopoiesis during ontogenesis of oyster.

Transcriptome sequencing reveals the involvement of reactive oxygen species in the hematopoiesis from Chinese mitten crab Eriocheir sinensis

Reactive oxygen species (ROS) produced in vivo during various electron transfer reactions are generally kept at a certain level since they are harmful to cells. However, it can sensitize hematopoietic progenitors to differentiation, and plays a signaling role in the regulation of hematopoietic cell fate. In the present study, the transcriptomes of crab HPT and hemocytes were sequenced using the Ion Torrent Proton sequencing platform. A total of 51,229,690 single end reads were obtained from six single-end libraries, which were assembled into 31346 unireads as reference. After mapping and transcript assembling, 362 differently expressed genes were identified and 301 of them were deemed to be more abundant in HPT. GO annotation revealed that they were mostly implicated in DNA, RNA and protein synthesis, cell division, mitochondria activities and energy metabolism. The expression level of mitochondrial complexes I (mitochondrial NADH-ubiquinone oxidoreductase) which was the main natural producers of mitochondrial ROS was found to be 8.6-fold (p < 0.01) higher in HPT than that in hemocytes. In hemocytes, the proteinase genes associated with proPO activation from the 61 up-regulated genes in hemocytes were the main up-regulated genes which might be the potential markers for mature hemocytes. ROS level in HPT cells was relatively higher which was confirmed with the high expression level of mitochondria related genes identified by transcriptome sequencing. After the ROS level was depressed by N-acetyl-l-cysteine (NAC), the production of hemocytes from HPT was inhibited, and the recovery of the total hemocytes counts was delayed. These results collectively indicated that the genes in redox system were more active in HPT, and ROS could function as an important modulator in the hematopoiesis of crab and promote the production of hemocytes from HPT.

WSSV-responsive gene expression under the influence of PmVRP15 suppression

The viral responsive protein 15 from black tiger shrimp Penaeus monodon (PmVRP15), is highly up-regulated and produced in the hemocytes of shrimp with white spot syndrome virus (WSSV) infection. To investigate the differential expression of genes from P. monodon hemocytes that are involved in WSSV infection under the influence of PmVRP15 expression, suppression subtractive hybridization (SSH) of PmVRP15-silenced shrimp infected with WSSV was performed. The 189 cDNA clones of the forward library were generated by subtracting the cDNAs from WSSV-infected and PmVRP15 knockdown shrimp with cDNAs from WSSV-infected and GFP knockdown shrimp. For the opposite subtraction, the 176 cDNA clones in the reverse library was an alternative set of genes in WSSV-infected shrimp hemocytes in the presence of PmVRP15 expression. The abundant genes in forward SSH library had a defense/homeostasis of 26%, energy/metabolism of 23% and in the reverse SSH library a hypothetical protein with unknown function was found (30%). The differential expressed immune-related genes from each library were selected for expression analysis using qRT-PCR. All selected genes from the forward library showed high up-regulation in the WSSV-challenged PmVRP15 knockdown group as expected. Interestingly, PmHHAP, a hemocyte homeostasis associated protein, and granulin-like protein, a conserved growth factor, are extremely up-regulated in the absence of PmVRP15 expression in WSSV-infected shrimp. Only transcript level of transglutaminase II, that functions in regulating hematopoietic tissue differentiation and inhibits mature hemocyte production in shrimp, was obviously down-regulated as observed from SSH results. Taken together, our results suggest that PmVRP15 might have a function relevant to hemocyte homeostasis during WSSV infection.

P.2.d.011 - Fronto-limbic connectivity during emotional processing in bipolar depression: the role of 5-HT1A promoter polymorphism

Hemocytes, the cellular component of invertebrate hemolymph, are essential for invertebrate immunity, but the hematopoiesis and regulation mechanism are still largely unknown. In the present study, a conserved hematopoietic transcription factor Cg-GATA2/3 was identified in Pacific oyster Crassotrea gigas, which was evolutionarily close to the vertebrate GATA1/2/3. Cg-GATA2/3 was mainly distributed in the immune organs, such as gill, hemocytes, and mantle. After Cg-GATA2/3 was interferenced by dsRNA, the mRNA expressions of hemocytes specific gene (EcSOD) and hematopoietic transcription factor (C-Myb) were all significant down-regulated, and the hemocyte renewal rates also decreased both in hemolymph and gill. During the larval developmental stages, the mRNA transcripts of Cg-GATA2/3 increased immediately after fertilization and kept a high level during blastula and early trochophore larvae stage (4-10 hpf, hours post fertilization), then decreased sharply in early D-veliger larvae stage (15 hpf). Whole-mount immunofluorescence assay further revealed that the abundant immunoreactivity of Cg-GATA2/3 was distributed in the whole body of blastula and gastrula embryos, while specialized gradually to a ring structure around the dorsal region in trochophore larvae. In the D-veliger and umbo larvae, scattered positive signals appeared in the specific sinus structure on the dorsal side and velum region. These results demonstrated that Cg-GATA2/3 was a hematopoietic lineage-specific transcription factor to regulate the hemocyte production, and it could also be used as hematopoietic specific marker to trace potential developmental events of hematopoiesis during ontogenesis of oyster.

Modulation of occluding junctions alters the hematopoietic niche to trigger immune activation.

Stem cells are regulated by signals from their microenvironment, or niche. During Drosophila hematopoiesis, a niche regulates prohemocytes to control hemocyte production. Immune challenges activate cell-signalling to initiate the cellular and innate immune response. Specifically, certain immune challenges stimulate the niche to produce signals that induce prohemocyte differentiation. However, the mechanisms that promote prohemocyte differentiation subsequent to immune challenges are poorly understood. Here we show that bacterial infection induces the cellular immune response by modulating occluding-junctions at the hematopoietic niche. Occluding-junctions form a permeability barrier that regulates the accessibility of prohemocytes to niche derived signals. The immune response triggered by infection causes barrier breakdown, altering the prohemocyte microenvironment to induce immune cell production. Moreover, genetically induced barrier ablation provides protection against infection by activating the immune response. Our results reveal a novel role for occluding-junctions in regulating niche-hematopoietic progenitor signalling and link this mechanism to immune cell production following infection.

Superparasitism, immune response and optimum progeny yield in the gregarious parasitoid Palmistichus elaeisis.

The subsequent deposition of an egg clutch by a female parasitoid into a host already parasitised either by itself or a conspecific (i.e. superparasitism) is a counterintuitive adaptive strategy, particularly considering the female parasitoid's ability to recognise the parasitised hosts. Such a scenario suggests that the adaptive value of superparasitism depends on the number of clutches laid in the same host, with consequences for parasitoid progeny yield. Here, we tested whether such is the case for the gregarious parasitoid Palmistichus elaeisis and explored its underlying basis. Allowing female parasitoids to lay multiple egg clutches in a single melonworm host pupa, parasitoid progeny and fitness exhibited a peak or optimum at three egg clutches laid per host pupa. In addition, haemocyte count, encapsulation and melanisation decreased with the number of egg clutches laid per host pupa. An optimum number of three clutches laid per host pupa was detected for P. elaeisis. As immune response via haemocyte production, encapsulation and melanisation decreased with the number of clutches laid per host, the higher parasitoid yield and fitness observed is the likely consequence of a compromised immune response coupled with an accommodative (i.e. scramble) larval competitive strategy allowing enough resources for optimum balance of parasitoid number and quality produced. © 2017 Society of Chemical Industry.

The receptor for activated C kinase 1 (RACK1) functions in hematopoiesis through JNK activation in Chinese mitten crab Eriocheir sinensis

Receptor for activated C kinase 1 (RACK1) is a WD-domain repeating protein which involves in the mediation of various biological processes, including innate immune response. In the present study, a RACK1 (designed as EsRACK1) gene from Chinese mitten crab E. sinensis was cloned by rapid amplification of cDNA ends (RACE) technique. The full-length cDNA sequence of EsRACK1 was of 1117 bp with an open reading frame (ORF) of 957 bp encoding a polypeptide of 318 amino acids containing seven WD repeats. EsRACK1 shared 62%–99% similarities with previously identified RACK1s in amino acid sequence, and it was clustered with the RACK1 from Pacifastacus leniusculus in the phylogenetic tree. The mRNA transcripts of EsRACK1 were constitutively expressed in various tissues with the highest expression level in hepatopancreas. The expression of EsRACK1 mRNA in hemocytes were significantly up-regulated post the stimulations with Vibrio anguillarum and Pichia pastoris. After exposure to CdCl2 and pentachlorophenol, the transcripts of EsRACK1 in hemocytes were up-regulated at the late phase from 12 h. When EsRACK1 was knocked down by dsRNA based RNAi, the total hemocyte counts, new-born hemocytes and phosphorylation of JNK were all significantly decreased. In addition, EsRACK1 transcription and phosphorylation of JNK were both decreased in hematopoietic tissue post Aeromonas hydrophila challenge. All the results suggested that EsRACK1 was involved in the innate immune response of the crab and participated in the production of new-born hemocytes through activation of JNK.