Publications by authors named "Yannick Gueguen"

45 Publications

In situ characterisation of pathogen dynamics during a Pacific oyster mortality syndrome episode.

Mar Environ Res 2021 Mar 9;165:105251. Epub 2021 Jan 9.

MARBEC, Univ Montpellier, CNRS, Ifremer, IRD, Sète, France.

Significant mortality of Crassostrea gigas juveniles is observed systematically every year worldwide. Pacific Oyster Mortality Syndrome (POMS) is caused by Ostreid Herpesvirus 1 (OsHV-1) infection leading to immune suppression, followed by bacteraemia caused by a consortium of opportunistic bacteria. Using an in-situ approach and pelagic chambers, our aim in this study was to identify pathogen dynamics in oyster flesh and in the water column during the course of a mortality episode in the Mediterranean Thau lagoon (France). OsHV-1 concentrations in oyster flesh increased before the first clinical symptoms of the disease appeared, reached maximum concentrations during the moribund phase and the mortality peak. The structure of the bacterial community associated with oyster flesh changed in favour of bacterial genera previously associated with oyster mortality including Vibrio, Arcobacter, Psychrobium, and Psychrilyobacter. During the oyster mortality episode, releases of OsHV-1 and opportunistic bacteria were observed, in succession, in the water surrounding the oyster lanterns. These releases may favour the spread of disease within oyster farms and potentially impact other marine species, thereby reducing marine biodiversity in shellfish farming areas.
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http://dx.doi.org/10.1016/j.marenvres.2020.105251DOI Listing
March 2021

Contribution of Viral Genomic Diversity to Oyster Susceptibility in the Pacific Oyster Mortality Syndrome.

Front Microbiol 2020 10;11:1579. Epub 2020 Jul 10.

IHPE, Université de Montpellier, CNRS, Ifremer, Université de Perpignan Via Domitia, Montpellier, France.

Juvenile Pacific oysters () are subjected to recurrent episodes of mass mortalities that constitute a threat for the oyster industry. This mortality syndrome named "Pacific Oyster Mortality Syndrome" (POMS) is a polymicrobial disease whose pathogenesis is initiated by a primary infection by a variant of an Ostreid herpes virus named OsHV-1 μVar. The characterization of the OsHV-1 genome during different disease outbreaks occurring in different geographic areas has revealed the existence of a genomic diversity for OsHV-1 μVar. However, the biological significance of this diversity is still poorly understood. To go further in understanding the consequences of OsHV-1 diversity on POMS, we challenged five biparental families of oysters to two different infectious environments on the French coasts (Atlantic and Mediterranean). We observed that the susceptibility to POMS can be different among families within the same environment but also for the same family between the two environments. Viral diversity analysis revealed that Atlantic and Mediterranean POMS are caused by two distinct viral populations. Moreover, we observed that different oyster families are infected by distinct viral populations within a same infectious environment. Altogether these results suggest that the co-evolutionary processes at play between OsHV-1 μVar and oyster populations have selected a viral diversity that could facilitate the infection process and the transmission in oyster populations. These new data must be taken into account in the development of novel selective breeding programs better adapted to the oyster culture environment.
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http://dx.doi.org/10.3389/fmicb.2020.01579DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7381293PMC
July 2020

Microbiota Composition and Evenness Predict Survival Rate of Oysters Confronted to Pacific Oyster Mortality Syndrome.

Front Microbiol 2020 27;11:311. Epub 2020 Feb 27.

IHPE, Univ. Montpellier, CNRS, Ifremer, Univ. Perpignan Via Domitia, Perpignan, France.

Pacific Oyster Mortality Syndrome (POMS) affects oysters worldwide and causes important economic losses. Disease dynamic was recently deciphered and revealed a multiple and progressive infection caused by the OsHV-1 μVar, triggering an immunosuppression followed by microbiota destabilization and bacteraemia by opportunistic bacterial pathogens. However, it remains unknown if microbiota might participate to protect oysters against POMS, and if microbiota characteristics might be predictive of oyster mortalities. To tackle this issue, we transferred full-sib progenies of resistant and susceptible oyster families from hatchery to the field during a period in favor of POMS. After 5 days of transplantation, oysters from each family were either sampled for individual microbiota analyses using 16S rRNA gene-metabarcoding or transferred into facilities to record their survival using controlled condition. As expected, all oysters from susceptible families died, and all oysters from the resistant family survived. Quantification of OsHV-1 and bacteria showed that 5 days of transplantation were long enough to contaminate oysters by POMS, but not for entering the pathogenesis process. Thus, it was possible to compare microbiota characteristics between resistant and susceptible oysters families at the early steps of infection. Strikingly, we found that microbiota evenness and abundances of Cyanobacteria (Subsection III, family I), Mycoplasmataceae, Rhodobacteraceae, and Rhodospirillaceae were significantly different between resistant and susceptible oyster families. We concluded that these microbiota characteristics might predict oyster mortalities.
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http://dx.doi.org/10.3389/fmicb.2020.00311DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7056673PMC
February 2020

A Sustained Immune Response Supports Long-Term Antiviral Immune Priming in the Pacific Oyster, Crassostrea gigas.

mBio 2020 03 10;11(2). Epub 2020 Mar 10.

IHPE, University of Montpellier, CNRS, Ifremer, University of Perpignan Via Domitia, Montpellier, France

Over the last decade, innate immune priming has been evidenced in many invertebrate phyla. If mechanistic models have been proposed, molecular studies aiming to substantiate these models have remained scarce. We reveal here the transcriptional signature associated with immune priming in the oyster Oysters were fully protected against Ostreid herpesvirus 1 (OsHV-1), a major oyster pathogen, after priming with poly(I·C), which mimics viral double-stranded RNA. Global analysis through RNA sequencing of oyster and viral genes after immune priming and viral infection revealed that poly(I·C) induces a strong antiviral response that impairs OsHV-1 replication. Protection is based on a sustained upregulation of immune genes, notably genes involved in the interferon pathway and apoptosis, which control subsequent viral infection. This persistent antiviral alert state remains active over 4 months and supports antiviral protection in the long term. This acquired resistance mechanism reinforces the molecular foundations of the sustained response model of immune priming. It further opens the way to applications (pseudovaccination) to cope with a recurrent disease that causes dramatic economic losses in the shellfish farming industry worldwide. In the last decade, important discoveries have shown that resistance to reinfection can be achieved without a functional adaptive immune system, introducing the concept of innate immune memory in invertebrates. However, this field has been constrained by the limited number of molecular mechanisms evidenced to support these phenomena. Taking advantage of an invertebrate species, the Pacific oyster (), in which we evidenced one of the longest and most effective periods of protection against viral infection observed in an invertebrate, we provide the first comprehensive transcriptomic analysis of antiviral innate immune priming. We show that priming with poly(I·C) induced a massive upregulation of immune-related genes, which control subsequent viral infection, and it was maintained for over 4 months after priming. This acquired resistant mechanism reinforces the molecular foundations of the sustained response model of immune priming. It opens the way to pseudovaccination to prevent the recurrent diseases that currently afflict economically or ecologically important invertebrates.
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http://dx.doi.org/10.1128/mBio.02777-19DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7064767PMC
March 2020

Differential basal expression of immune genes confers Crassostrea gigas resistance to Pacific oyster mortality syndrome.

BMC Genomics 2020 Jan 20;21(1):63. Epub 2020 Jan 20.

IHPE, Université de Montpellier, CNRS, Ifremer, Université de Perpignan Via Domitia, Place E. Bataillon, CC080, 34095, Montpellier, France.

Background: As a major threat to the oyster industry, Pacific Oyster Mortality Syndrome (POMS) is a polymicrobial disease affecting the main oyster species farmed across the world. POMS affects oyster juveniles and became panzootic this last decade, but POMS resistance in some oyster genotypes has emerged. While we know some genetic loci associated with resistance, the underlying mechanisms remained uncharacterized. So, we developed a comparative transcriptomic approach using basal gene expression profiles between different oyster biparental families with contrasted phenotypes when confronted to POMS (resistant or susceptible).

Results: We showed that POMS resistant oysters show differential expression of genes involved in stress responses, protein modifications, maintenance of DNA integrity and repair, and immune and antiviral pathways. We found similarities and clear differences among different molecular pathways in the different resistant families. These results suggest that the resistance process is polygenic and partially varies according to the oyster genotype.

Conclusions: We found differences in basal expression levels of genes related to TLR-NFκB, JAK-STAT and STING-RLR pathways. These differences could explain the best antiviral response, as well as the robustness of resistant oysters when confronted to POMS. As some of these genes represent valuable candidates for selective breeding, we propose future studies should further examine their function.
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http://dx.doi.org/10.1186/s12864-020-6471-xDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6971885PMC
January 2020

Immune-suppression by OsHV-1 viral infection causes fatal bacteraemia in Pacific oysters.

Nat Commun 2018 10 11;9(1):4215. Epub 2018 Oct 11.

IHPE, Université de Montpellier, CNRS, Ifremer, Université de Perpignan Via Domitia, Place E. Bataillon, 34095, Montpellier, France.

Infectious diseases are mostly explored using reductionist approaches despite repeated evidence showing them to be strongly influenced by numerous interacting host and environmental factors. Many diseases with a complex aetiology therefore remain misunderstood. By developing a holistic approach to tackle the complexity of interactions, we decipher the complex intra-host interactions underlying Pacific oyster mortality syndrome affecting juveniles of Crassostrea gigas, the main oyster species exploited worldwide. Using experimental infections reproducing the natural route of infection and combining thorough molecular analyses of oyster families with contrasted susceptibilities, we demonstrate that the disease is caused by multiple infection with an initial and necessary step of infection of oyster haemocytes by the Ostreid herpesvirus OsHV-1 µVar. Viral replication leads to the host entering an immune-compromised state, evolving towards subsequent bacteraemia by opportunistic bacteria. We propose the application of our integrative approach to decipher other multifactorial diseases that affect non-model species worldwide.
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http://dx.doi.org/10.1038/s41467-018-06659-3DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6182001PMC
October 2018

Inefficient immune response is associated with microbial permissiveness in juvenile oysters affected by mass mortalities on field.

Fish Shellfish Immunol 2018 Jun 19;77:156-163. Epub 2018 Mar 19.

IHPE, Université de Montpellier, CNRS, Ifremer, Université de Perpignan, Via Domitia, France.

Since 2008, juvenile Crassostrea gigas oysters have suffered from massive mortalities in European farming areas. This disease of complex etiology is still incompletely understood. Triggered by an elevated seawater temperature, it has been associated to infections by a herpes virus named OsHV-1 as well as pathogenic vibrios of the Splendidus clade. Ruling out the complexity of the disease, most of our current knowledge has been acquired in controlled experiments. Among the many unsolved questions, it is still ignored what role immunity plays in the capacity oysters have to survive an infectious episode. Here we show that juvenile oysters susceptible to the disease mount an inefficient immune response associated with microbial permissiveness and death. We found that, in contrast to resistant adult oysters having survived an earlier episode of mortality, susceptible juvenile oysters never exposed to infectious episodes died by more than 90% in a field experiment. Susceptible oysters were heavily colonized by OsHV-1 herpes virus as well as bacteria including vibrios potentially pathogenic for oysters, which proliferated in oyster flesh and body fluids during the mortality event. Nonetheless, susceptible oysters were found to sense microbes as indicated by an overexpression of immune receptors and immune signaling pathways. However, they did not express important immune effectors involved in antimicrobial immunity and apoptosis and showed repressed expression of genes involved in ROS and metal homeostasis. This contrasted with resistant oysters, which expressed those important effectors, controlled bacterial and viral colonization and showed 100% survival to the mortality event. Altogether, our results demonstrate that the immune response mounted by susceptible oysters lacks some important immune functions and fails in controlling microbial proliferation. This study opens the way to more holistic studies on the "mass mortality syndrome", which are now required to decipher the sequence of events leading to oyster mortalities and determine the relative weight of pathogens, oyster genetics and oyster-associated microbiota in the disease.
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http://dx.doi.org/10.1016/j.fsi.2018.03.027DOI Listing
June 2018

Response of the pearl oyster Pinctada margaritifera to cadmium and chromium: Identification of molecular biomarkers.

Mar Pollut Bull 2017 May 18;118(1-2):420-426. Epub 2017 Mar 18.

Ifremer, UMR 241 EIO, UPF-ILM-IRD, Labex Corail, BP 49, 98719 Taravao, Tahiti, French Polynesia. Electronic address:

This study was designed to identify in the pearl oyster Pinctada margaritifera, used as a bio-accumulator, molecular biomarkers for the presence of heavy metals in the lagoon environment. Pearl oysters were exposed to 2 concentrations (1 and 10μgL) of cadmium (Cd) and chromium (Cr) compared to a control. Twelve target genes encoding proteins potentially involved in the response to heavy metal contamination with antioxidant, detoxification or apoptosis activities were selected. P. margaritifera accumulated Cd but not Cr, and mortality was related to the amount of Cd accumulated in tissues. In response to Cd-Cr contamination, metallothionein (MT) was significantly up-regulated by Cd-Cr at both concentrations, while 7 others (SOD, CAT, GPX, GSTO, GSTM, CASP, MDR) were down-regulated. Based on the development of these molecular tools, we propose that the pearl oyster, P. margaritifera, could be used as a sentinel species for heavy metal contamination in the lagoons of tropical ecosystems.
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http://dx.doi.org/10.1016/j.marpolbul.2017.03.012DOI Listing
May 2017

An updated assessment of spp. that associate with common scleractinian corals from Moorea (French Polynesia) reveals high diversity among background symbionts and a novel finding of clade B.

PeerJ 2017 5;5:e2856. Epub 2017 Jan 5.

PSL CRIOBE USR3278 CNRS-EPHE-UPVD, Labex CORAIL, Papetoai, Moorea, French Polynesia; Current affiliation:  UMR250/9220 ENTROPIE IRD-CNRS-UR, Labex CORAIL, Promenade Roger-Laroque, Noumea cedex, New Caledonia, France.

The adaptative bleaching hypothesis (ABH) states that, depending on the symbiotic flexibility of coral hosts (i.e., the ability of corals to "switch" or "shuffle" their algal symbionts), coral bleaching can lead to a change in the composition of their associated community and, thus, contribute to the coral's overall survival. In order to determine the flexibility of corals, molecular tools are required to provide accurate species delineations and to detect low levels of coral-associated . Here, we used highly sensitive quantitative (real-time) PCR (qPCR) technology to analyse five common coral species from Moorea (French Polynesia), previously screened using only traditional molecular methods, to assess the presence of low-abundance (background) spp. Similar to other studies, each coral species exhibited a strong specificity to a particular clade, irrespective of the environment. In addition, however, each of the five species harboured at least one additional clade, among clades A-D, at background levels. Unexpectedly, and for the first time in French Polynesia, clade B was detected as a coral symbiont. These results increase the number of known coral- associations from corals found in French Polynesia, and likely indicate an underestimation of the ability of the corals in this region to associate with and/or "shuffle" different clades. Altogether our data suggest that corals from French Polynesia may favor a trade-off between optimizing symbioses with a specific clade(s), maintaining associations with particular background clades that may play a role in the ability of corals to respond to environmental change.
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http://dx.doi.org/10.7717/peerj.2856DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5289445PMC
January 2017

Bacterial community characterization of water and intestine of the shrimp Litopenaeus stylirostris in a biofloc system.

BMC Microbiol 2016 07 19;16(1):157. Epub 2016 Jul 19.

Ifremer, UMR 241 EIO, UPF-ILM-IRD, Labex Corail, B.P. 7004, 98719, Taravao, Tahiti, French Polynesia.

Background: Biofloc technology (BFT), a rearing method with little or no water exchange, is gaining popularity in aquaculture. In the water column, such systems develop conglomerates of microbes, algae and protozoa, together with detritus and dead organic particles. The intensive microbial community presents in these systems can be used as a pond water quality treatment system, and the microbial protein can serve as a feed additive. The current problem with BFT is the difficulty of controlling its bacterial community composition for both optimal water quality and optimal shrimp health. The main objective of the present study was to investigate microbial diversity of samples obtained from different culture environments (Biofloc technology and clear seawater) as well as from the intestines of shrimp reared in both environments through high-throughput sequencing technology.

Results: Analyses of the bacterial community identified in water from BFT and "clear seawater" (CW) systems (control) containing the shrimp Litopenaeus stylirostris revealed large differences in the frequency distribution of operational taxonomic units (OTUs). Four out of the five most dominant bacterial communities were different in both culture methods. Bacteria found in great abundance in BFT have two principal characteristics: the need for an organic substrate or nitrogen sources to grow and the capacity to attach to surfaces and co-aggregate. A correlation was found between bacteria groups and physicochemical and biological parameters measured in rearing tanks. Moreover, rearing-water bacterial communities influenced the microbiota of shrimp. Indeed, the biofloc environment modified the shrimp intestine microbiota, as the low level (27 %) of similarity between intestinal bacterial communities from the two treatments.

Conclusion: This study provides the first information describing the complex biofloc microbial community, which can help to understand the environment-microbiota-host relationship in this rearing system.
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http://dx.doi.org/10.1186/s12866-016-0770-zDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4952143PMC
July 2016

Antimicrobial peptides in marine invertebrate health and disease.

Philos Trans R Soc Lond B Biol Sci 2016 05;371(1695)

CNRS, Université de Montpellier, Interactions Hôtes-Pathogènes-Environnements (IHPE, UMR5244), Place Eugène Bataillon, 34090 Montpellier cedex, France Ifremer, Université de Montpellier, Interactions Hôtes-Pathogènes-Environnements (IHPE, UMR5244), Place Eugène Bataillon, 34090 Montpellier cedex, France UPVD, Université de Montpellier, Interactions Hôtes-Pathogènes-Environnements (IHPE, UMR5244), Place Eugène Bataillon, 34090 Montpellier cedex, France Université de Montpellier, Interactions Hôtes-Pathogènes-Environnements (IHPE, UMR5244), Place Eugène Bataillon, 34090 Montpellier cedex, France.

Aquaculture contributes more than one-third of the animal protein from marine sources worldwide. A significant proportion of aquaculture products are derived from marine protostomes that are commonly referred to as 'marine invertebrates'. Among them, penaeid shrimp (Ecdysozosoa, Arthropoda) and bivalve molluscs (Lophotrochozoa, Mollusca) are economically important. Mass rearing of arthropods and molluscs causes problems with pathogens in aquatic ecosystems that are exploited by humans. Remarkably, species of corals (Cnidaria) living in non-exploited ecosystems also suffer from devastating infectious diseases that display intriguing similarities with those affecting farmed animals. Infectious diseases affecting wild and farmed animals that are present in marine environments are predicted to increase in the future. This paper summarizes the role of the main pathogens and their interaction with host immunity, with a specific focus on antimicrobial peptides (AMPs) and pathogen resistance against AMPs. We provide a detailed review of penaeid shrimp AMPs and their role at the interface between the host and its resident/pathogenic microbiota. We also briefly describe the relevance of marine invertebrate AMPs in an applied context.This article is part of the themed issue 'Evolutionary ecology of arthropod antimicrobial peptides'.
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http://dx.doi.org/10.1098/rstb.2015.0300DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4874397PMC
May 2016

Yes, it turns: experimental evidence of pearl rotation during its formation.

R Soc Open Sci 2015 Jul 15;2(7):150144. Epub 2015 Jul 15.

Ifremer , UMR 241 EIO, UPF-ILM-IRD, Labex Corail , BP 7004, 98719 Taravao, French Polynesia.

Cultured pearls are human creations formed by inserting a nucleus and a small piece of mantle tissue into a living shelled mollusc, usually a pearl oyster. Although many pearl observations intuitively suggest a possible rotation of the nucleated pearl inside the oyster, no experimental demonstration of such a movement has ever been done. This can be explained by the difficulty of observation of such a phenomenon in the tissues of a living animal. To investigate this question of pearl rotation, a magnetometer system was specifically engineered to register magnetic field variations with magnetic sensors from movements of a magnetic nucleus inserted in the pearl oyster. We demonstrated that a continuous movement of the nucleus inside the oyster starts after a minimum of 40 days post-grafting and continues until the pearl harvest. We measured a mean angular speed of 1.27° min(-1) calculated for four different oysters. Rotation variability was observed among oysters and may be correlated to pearl shape and defects. Nature's ability to generate so amazingly complex structures like a pearl has delivered one of its secrets.
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http://dx.doi.org/10.1098/rsos.150144DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4632584PMC
July 2015

Effect of temperature, food availability, and estradiol injection on gametogenesis and gender in the pearl oyster Pinctada margaritifera.

J Exp Zool A Ecol Genet Physiol 2016 Jan 20;325(1):13-24. Epub 2015 Oct 20.

Ifremer, UMR 241 Ecosystèmes Insulaires Océaniens (EIO), Labex CORAIL, Centre du Pacifique, Taravao, Tahiti, French Polynesia.

The black-lip pearl oyster Pinctada margaritifera is a protandrous hermaphrodite species. Its economic value has led to the development of controlled hatchery reproduction techniques, although many aspects remain to be optimized. In order to understand reproductive mechanisms and their controlling factors, two independent experiments were designed to test hypotheses of gametogenesis and sex ratio control by environmental and hormonal factors. In one, pearl oysters were exposed under controlled conditions at different combinations of temperature (24 and 28°C) and food level (10,000 and 40,000 cells mL(-1) ); whereas in the other, pearl oysters were conditioned under natural conditions into the lagoon and subjected to successive 17β-estradiol injections (100 μg per injection). Gametogenesis and sex ratio were assessed by histology for each treatment. In parallel, mRNA expressions of nine marker genes of the sexual pathway (pmarg-foxl2, pmarg-c43476, pmarg-c45042, pmarg-c19309, pmarg-c54338, pmarg-vit6, pmarg-zglp1, pmarg-dmrt, and pmarg-fem1-like) were investigated. Maximum maturation was observed in the treatment combining the highest temperature (28°C) and the highest microalgae concentration (40,000 cells mL(-1) ), where the female sex tended to be maintained. Injection of 17β-estradiol induced a significant increase of undetermined stage proportion 2 weeks after the final injection. These results suggest that gametogenesis and gender in adult pearl oysters can be controlled by environmental factors and estrogens. While there were no significant effects on relative gene expression, the 3-gene-pair expression ratio model of the sexual pathway of P. margaritifera, suggest a probable dominance of genetic sex determinism without excluding a mixed sex determination mode (genetic + environmental). J. Exp. Zool. 325A:13-24, 2016. © 2015 Wiley Periodicals, Inc.
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http://dx.doi.org/10.1002/jez.1992DOI Listing
January 2016

Identification of genes associated with shell color in the black-lipped pearl oyster, Pinctada margaritifera.

BMC Genomics 2015 Aug 1;16:568. Epub 2015 Aug 1.

Laboratoire d'Excellence "CORAIL", USR 3278 CNRS-CRIOBE- EPHE, Perpignan, France, Papetoai, Moorea, French Polynesia.

Background: Color polymorphism in the nacre of pteriomorphian bivalves is of great interest for the pearl culture industry. The nacreous layer of the Polynesian black-lipped pearl oyster Pinctada margaritifera exhibits a large array of color variation among individuals including reflections of blue, green, yellow and pink in all possible gradients. Although the heritability of nacre color variation patterns has been demonstrated by experimental crossing, little is known about the genes involved in these patterns. In this study, we identify a set of genes differentially expressed among extreme color phenotypes of P. margaritifera using a suppressive and subtractive hybridization (SSH) method comparing black phenotypes with full and half albino individuals.

Results: Out of the 358 and 346 expressed sequence tags (ESTs) obtained by conducting two SSH libraries respectively, the expression patterns of 37 genes were tested with a real-time quantitative PCR (RT-qPCR) approach by pooling five individuals of each phenotype. The expression of 11 genes was subsequently estimated for each individual in order to detect inter-individual variation. Our results suggest that the color of the nacre is partially under the influence of genes involved in the biomineralization of the calcitic layer. A few genes involved in the formation of the aragonite tablets of the nacre layer and in the biosynthesis chain of melanin also showed differential expression patterns. Finally, high variability in gene expression levels were observed within the black phenotypes.

Conclusions: Our results revealed that three main genetic processes were involved in color polymorphisms: the biomineralization of the nacreous and calcitic layers and the synthesis of pigments such as melanin, suggesting that color polymorphism takes place at different levels in the shell structure. The high variability of gene expression found within black phenotypes suggests that the present work should serve as a basis for future studies exploring more thoroughly the expression patterns of candidate genes within black phenotypes with different dominant iridescent colors.
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http://dx.doi.org/10.1186/s12864-015-1776-xDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4521380PMC
August 2015

Use of Natural Antimicrobial Peptides and Bacterial Biopolymers for Cultured Pearl Production.

Mar Drugs 2015 Jun 11;13(6):3732-44. Epub 2015 Jun 11.

AiMB. 17 Rue d'Ouessant, 29280 Plouzané, France.

Cultured pearls are the product of grafting and rearing of Pinctada margaritifera pearl oysters in their natural environment. Nucleus rejections and oyster mortality appear to result from bacterial infections or from an inappropriate grafting practice. To reduce the impact of bacterial infections, synthetic antibiotics have been applied during the grafting practice. However, the use of such antibiotics presents a number of problems associated with their incomplete biodegradability, limited efficacy in some cases, and an increased risk of selecting for antimicrobial resistant bacteria. We investigated the application of a marine antimicrobial peptide, tachyplesin, which is present in the Japanese horseshoe crab Tachypleus tridentatus, in combination with two marine bacterial exopolymers as alternative treatment agents. In field studies, the combination treatment resulted in a significant reduction in graft failures vs. untreated controls. The combination of tachyplesin (73 mg/L) with two bacterial exopolysaccharides (0.5% w/w) acting as filming agents, reduces graft-associated bacterial contamination. The survival data were similar to that reported for antibiotic treatments. These data suggest that non-antibiotic treatments of pearl oysters may provide an effective means of improving oyster survival following grafting procedures.
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http://dx.doi.org/10.3390/md13063732DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4483653PMC
June 2015

Rearing effect of biofloc on antioxidant and antimicrobial transcriptional response in Litopenaeus stylirostris shrimp facing an experimental sub-lethal hydrogen peroxide stress.

Fish Shellfish Immunol 2015 Aug 4;45(2):933-9. Epub 2015 Jun 4.

Ifremer, Centre Océanologique du Pacifique, Unité de recherche Resources Marines, B.P 7004, 98719, Taravao, French Polynesia; Ifremer, UMR 5244 IHPE, UPVD, CNRS, Université de Montpellier, F-34095, Montpellier, France.

This study compares the antioxidant and antimicrobial transcriptional expression of blue shrimps reared according to two different systems, BioFloc Technology (BFT) and Clear sea Water (CW) and their differential responses when facing an experimental sublethal hydrogen peroxide stress. After 30 days of rearing, juvenile shrimps were exposed to H2O2 stress at a concentration of 30 ppm during 6 h. The oxidative stress caused by H2O2 was examined in the digestive glands of the shrimp, in which antioxidant enzyme (AOE) and antimicrobial peptide (AMP) gene expression were analysed by quantitative real-time PCR. Results showed that rearing conditions did not affect the expression of genes encoding AOEs or AMPs. However, H2O2 stress induced a differential response in expression between shrimps from the two rearing treatments (BFT and CW). Comparative analysis of the expression profiles indicates that catalase transcripts were significantly upregulated by H2O2 stress for BFT shrimps while no change was observed for CW shrimps. In contrast, H2O2 caused down-regulation of superoxide dismutase and glutathione transferase transcripts and of the three AMP transcripts studied (penaeidin 2 and 3, and crustin) for CW shrimps, while no effect was observed on BFT shrimp transcript levels. These results suggested that BFT shrimps maintained antioxidant and AMP responses after stress and therefore can effectively protect their cells against oxidative stress, while CW shrimp immune competence seems to decrease after stress.
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http://dx.doi.org/10.1016/j.fsi.2015.05.041DOI Listing
August 2015

Molecular signatures discriminating the male and the female sexual pathways in the pearl oyster Pinctada margaritifera.

PLoS One 2015 27;10(3):e0122819. Epub 2015 Mar 27.

Ifremer, UMR 241 Ecosystèmes Insulaires Océaniens (EIO), Labex Corail, Centre du Pacifique, BP 7004, 98719 Taravao, Tahiti, French Polynesia.

The genomics of economically important marine bivalves is studied to provide better understanding of the molecular mechanisms underlying their different reproductive strategies. The recently available gonad transcriptome of the black-lip pearl oyster Pinctada margaritifera is a novel and powerful resource to study these mechanisms in marine mollusks displaying hermaphroditic features. In this study, RNAseq quantification data of the P. margaritifera gonad transcriptome were analyzed to identify candidate genes in histologically-characterized gonad samples to provide molecular signatures of the female and male sexual pathway in this pearl oyster. Based on the RNAseq data set, stringent expression analysis identified 1,937 contigs that were differentially expressed between the gonad histological categories. From the hierarchical clustering analysis, a new reproduction model is proposed, based on a dual histo-molecular analytical approach. Nine candidate genes were identified as markers of the sexual pathway: 7 for the female pathway and 2 for the male one. Their mRNA levels were assayed by real-time PCR on a new set of gonadic samples. A clustering method revealed four principal expression patterns based on the relative gene expression ratio. A multivariate regression tree realized on these new samples and validated on the previously analyzed RNAseq samples showed that the sexual pathway of P. margaritifera can be predicted by a 3-gene-pair expression ratio model of 4 different genes: pmarg-43476, pmarg-foxl2, pmarg-54338 and pmarg-fem1-like. This 3-gene-pair expression ratio model strongly suggests only the implication of pmarg-foxl2 and pmarg-fem1-like in the sex inversion of P. margaritifera. This work provides the first histo-molecular model of P. margaritifera reproduction and a gene expression signature of its sexual pathway discriminating the male and female pathways. These represent useful tools for understanding and studying sex inversion, sex differentiation and sex determinism in this species and other related species for aquaculture purposes such as genetic selection programs.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0122819PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4376701PMC
February 2016

Temperature and food influence shell growth and mantle gene expression of shell matrix proteins in the pearl oyster Pinctada margaritifera.

PLoS One 2014 14;9(8):e103944. Epub 2014 Aug 14.

Ifremer, UMR 241 « Ecosystèmes Insulaires Océaniens », Labex Corail, Centre du Pacifique, Taravao, Tahiti, Polynésie Française.

In this study, we analyzed the combined effect of microalgal concentration and temperature on the shell growth of the bivalve Pinctada margaritifera and the molecular mechanisms underlying this biomineralization process. Shell growth was measured after two months of rearing in experimental conditions, using calcein staining of the calcified structures. Molecular mechanisms were studied though the expression of 11 genes encoding proteins implicated in the biomineralization process, which was assessed in the mantle. We showed that shell growth is influenced by both microalgal concentration and temperature, and that these environmental factors also regulate the expression of most of the genes studied. Gene expression measurement of shell matrix protein thereby appears to be an appropriate indicator for the evaluation of the biomineralization activity in the pearl oyster P. margaritifera under varying environmental conditions. This study provides valuable information on the molecular mechanisms of mollusk shell growth and its environmental control.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0103944PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4133174PMC
April 2015

Gonad transcriptome analysis of pearl oyster Pinctada margaritifera: identification of potential sex differentiation and sex determining genes.

BMC Genomics 2014 Jun 18;15:491. Epub 2014 Jun 18.

Ifremer, UMR 241 EIO, Labex CORAIL, BP 7004, 98719 Taravao, Tahiti, Polynésie Française.

Background: Black pearl farming is based on culture of the blacklip pearl oyster Pinctada margaritifera (Mollusca, lophotrochozoa), a protandrous hermaphrodite species. At first maturation, all individuals are males. The female sex appears progressively from two years old, which represents a limitation for broodstock conditioning for aquaculture production. In marine mollusks displaying hermaphroditic features, data on sexual determinism and differentiation, including the molecular sex determining cascade, are scarce. To increase genomic resources and identify the molecular mechanisms whereby gene expression may act in the sexual dimorphism of P. margaritifera, we performed gonad transcriptome analysis.

Results: The gonad transcriptome of P. margaritifera was sequenced from several gonadic samples of males and females at different development stages, using a Next-Generation-Sequencing method and RNAseq technology. After Illumina sequencing, assembly and annotation, we obtained 70,147 contigs of which 62.2% shared homologies with existing protein sequences, and 9% showed functional annotation with Gene Ontology terms. Differential expression analysis identified 1,993 differentially expressed contigs between the different categories of gonads. Clustering methods of samples revealed that the sex explained most of the variation in gonad gene expression. K-means clustering of differentially expressed contigs showed 815 and 574 contigs were more expressed in male and female gonads, respectively. The analysis of these contigs revealed the presence of known specific genes coding for proteins involved in sex determinism and/or differentiation, such as dmrt and fem-1 like for males, or foxl2 and vitellogenin for females. The specific gene expression profiles of pmarg-fem1-like, pmarg-dmrt and pmarg-foxl2 in different reproductive stages (undetermined, sexual inversion and regression) suggest that these three genes are potentially involved in the sperm-oocyte switch in P. margaritifera.

Conclusions: The study provides a new transcriptomic tool to study reproduction in hermaphroditic marine mollusks. It identifies sex differentiation and potential sex determining genes in P. margaritifera, a protandrous hermaphrodite species.
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http://dx.doi.org/10.1186/1471-2164-15-491DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4082630PMC
June 2014

Functional divergence in shrimp anti-lipopolysaccharide factors (ALFs): from recognition of cell wall components to antimicrobial activity.

PLoS One 2013 4;8(7):e67937. Epub 2013 Jul 4.

Ecologie des Systèmes Marins Côtiers, UMR5119, Centre National de la Recherche Scientifique, Institut de la Recherche pour le Développement, Université Montpellier 1, Montpellier, France.

Antilipopolysaccharide factors (ALFs) have been described as highly cationic polypeptides with a broad spectrum of potent antimicrobial activities. In addition, ALFs have been shown to recognize LPS, a major component of the Gram-negative bacteria cell wall, through conserved amino acid residues exposed in the four-stranded β-sheet of their three dimensional structure. In penaeid shrimp, ALFs form a diverse family of antimicrobial peptides composed by three main variants, classified as ALF Groups A to C. Here, we identified a novel group of ALFs in shrimp (Group D ALFs), which corresponds to anionic polypeptides in which many residues of the LPS binding site are lacking. Both Group B (cationic) and Group D (anionic) shrimp ALFs were produced in a heterologous expression system. Group D ALFs were found to have impaired LPS-binding activities and only limited antimicrobial activity compared to Group B ALFs. Interestingly, all four ALF groups were shown to be simultaneously expressed in an individual shrimp and to follow different patterns of gene expression in response to a microbial infection. Group B was by far the more expressed of the ALF genes. From our results, nucleotide sequence variations in shrimp ALFs result in functional divergence, with significant differences in LPS-binding and antimicrobial activities. To our knowledge, this is the first functional characterization of the sequence diversity found in the ALF family.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0067937PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3701609PMC
February 2014

Different secretory repertoires control the biomineralization processes of prism and nacre deposition of the pearl oyster shell.

Proc Natl Acad Sci U S A 2012 Dec 3;109(51):20986-91. Epub 2012 Dec 3.

Ifremer, Centre Ifremer du Pacifique, Unité Mixte de Recherche 241 Ecosystèmes Insulaires Océaniens, Tahiti, 98719 Taravao, French Polynesia.

Mollusca evolutionary success can be attributed partly to their efficiency to sustain and protect their soft body with an external biomineralized structure, the shell. Current knowledge of the protein set responsible for the formation of the shell microstructural polymorphism and unique properties remains largely patchy. In Pinctada margaritifera and Pinctada maxima, we identified 80 shell matrix proteins, among which 66 are entirely unique. This is the only description of the whole "biomineralization toolkit" of the matrices that, at least in part, is thought to regulate the formation of the prismatic and nacreous shell layers in the pearl oysters. We unambiguously demonstrate that prisms and nacre are assembled from very different protein repertoires. This suggests that these layers do not derive from each other.
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http://dx.doi.org/10.1073/pnas.1210552109DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3529032PMC
December 2012

Expression, tissue localization and synergy of antimicrobial peptides and proteins in the immune response of the oyster Crassostrea gigas.

Dev Comp Immunol 2012 Jul 31;37(3-4):363-70. Epub 2012 Jan 31.

Ifremer, UMR5119 Écologie des Systèmes Marins Côtiers, Place Eugène Bataillon, 34095 Montpellier Cedex 5, France.

Diverse families of antimicrobial peptides and proteins have been described in oysters. We investigated here how antimicrobials are involved in the immune response against a pathogenic strain of Vibrio splendidus. Oyster antimicrobials were shown to display a wide variety of expression profiles in hemocyte populations and tissues. Oyster defensins are constitutively expressed in specific tissues such as mantle (Cg-Defm) or hemocytes (Cg-Defhs), while Cg-BPI is inducible and Cg-Prp appears down-regulated in hemocytes upon infection. The migratory behavior of hemocytes that express the different antimicrobials was found to be involved in the oyster response to a pathogenic Vibrio infection. Indeed, it contributes to colocalize several antimicrobials that were shown here to have synergistic activities. We propose that such a synergy, which was evidenced both within and between families of antimicrobials, might compensate for the low concentration of antimicrobials in oyster tissues.
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http://dx.doi.org/10.1016/j.dci.2012.01.004DOI Listing
July 2012

Characterization of MRNP34, a novel methionine-rich nacre protein from the pearl oysters.

Amino Acids 2012 May 18;42(5):2009-17. Epub 2011 May 18.

Ifremer, LBQP, Centre Océanologique du Pacifique, Taravao, French Polynesia.

Nacre of the Pinctada pearl oyster shells is composed of 98% CaCO3 and 2% organic matrix. The relationship between the organic matrix and the mechanism of nacre formation currently constitutes the main focus regarding the biomineralization process. In this study, we isolated a new nacre matrix protein in P. margaritifera and P. maxima, we called Pmarg- and Pmax-MRNP34 (methionine-rich nacre protein). MRNP34 is a secreted hydrophobic protein, which is remarkably rich in methionine, and which is specifically localised in mineralizing the epithelium cells of the mantle and in the nacre matrix. The structure of this protein is drastically different from those of the other nacre proteins already described. This unusual methionine-rich protein is a new member in the growing list of low complexity domain containing proteins that are associated with biocalcifications. These observations offer new insights to the molecular mechanisms of biomineralization.
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http://dx.doi.org/10.1007/s00726-011-0932-0DOI Listing
May 2012

Transcriptome and proteome analysis of Pinctada margaritifera calcifying mantle and shell: focus on biomineralization.

BMC Genomics 2010 Nov 1;11:613. Epub 2010 Nov 1.

Ifremer - Laboratoire de Biotechnologie et de Qualité de Perle, Centre Océanologique du Pacifique - BP 7004, 98719 Taravao, French Polynesia.

Background: The shell of the pearl-producing bivalve Pinctada margaritifera is composed of an organic cell-free matrix that plays a key role in the dynamic process of biologically-controlled biomineralization. In order to increase genomic resources and identify shell matrix proteins implicated in biomineralization in P. margaritifera, high-throughput Expressed Sequence Tag (EST) pyrosequencing was undertaken on the calcifying mantle, combined with a proteomic analysis of the shell.

Results: We report the functional analysis of 276 738 sequences, leading to the constitution of an unprecedented catalog of 82 P. margaritifera biomineralization-related mantle protein sequences. Components of the current "chitin-silk fibroin gel-acidic macromolecule" model of biomineralization processes were found, in particular a homolog of a biomineralization protein (Pif-177) recently discovered in P. fucata. Among these sequences, we could show the localization of two other biomineralization protein transcripts, pmarg-aspein and pmarg-pearlin, in two distinct areas of the outer mantle epithelium, suggesting their implication in calcite and aragonite formation. Finally, by combining the EST approach with a proteomic mass spectrometry analysis of proteins isolated from the P. margaritifera shell organic matrix, we demonstrated the presence of 30 sequences containing almost all of the shell proteins that have been previously described from shell matrix protein analyses of the Pinctada genus. The integration of these two methods allowed the global composition of biomineralizing tissue and calcified structures to be examined in tandem for the first time.

Conclusions: This EST study made on the calcifying tissue of P. margaritifera is the first description of pyrosequencing on a pearl-producing bivalve species. Our results provide direct evidence that our EST data set covers most of the diversity of the matrix protein of P. margaritifera shell, but also that the mantle transcripts encode proteins present in P. margaritifera shell, hence demonstrating their implication in shell formation. Combining transcriptomic and proteomic approaches is therefore a powerful way to identify proteins involved in biomineralization. Data generated in this study supply the most comprehensive list of biomineralization-related sequences presently available among protostomian species, and represent a major breakthrough in the field of molluskan biomineralization.
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http://dx.doi.org/10.1186/1471-2164-11-613DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3091754PMC
November 2010

Molecular diversity of antimicrobial effectors in the oyster Crassostrea gigas.

BMC Evol Biol 2010 Jan 25;10:23. Epub 2010 Jan 25.

Ifremer, CNRS, Université de Montpellier II, IRD, UMR 5119 Ecosystèmes Lagunaires, Place Eugène Bataillon, CC80, 34095 Montpellier, France.

Background: To gain insight into the molecular diversity of antimicrobial peptides and proteins in the oyster Crassostrea gigas, we characterized and compared the sequence polymorphism of the antimicrobial peptides (AMPs), Cg-Defensins (Cg-Defs) and Cg-Proline Rich peptide (Cg-Prp), and of the bactericidal permeability increasing protein, Cg-BPI. For that, we analyzed genomic and transcript sequences obtained by specific PCR amplification and in silico searches.

Results: High diversification among the three antimicrobial effectors was evidenced by this polymorphism survey. On the basis of sequence phylogenies, each AMP aggregates into clearly defined groups of variants and is the product of a multigenic family displaying a variety of gene structures. In contrast, Cg-bpi forms a single group and is encoded by a single gene copy. Moreover, we identified for both AMPs several genetic mechanisms of diversification such as recombination, parallel mutations leading to phylogenetic homoplasy and indel events. In addition, the non synonymous to synonymous substitutions ratio by codon (dN/dS) revealed several negatively and positively selected sites for both AMPs, suggesting that directional selection pressures have shaped their sequence variations.

Conclusions: This study shows for the first time in a mollusc that antimicrobial peptides and proteins have been subject to distinct patterns of diversification and we evidence the existence of different evolutionary routes leading to such sequence variability.
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http://dx.doi.org/10.1186/1471-2148-10-23DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2823732PMC
January 2010

Generation and analysis of a 29,745 unique Expressed Sequence Tags from the Pacific oyster (Crassostrea gigas) assembled into a publicly accessible database: the GigasDatabase.

BMC Genomics 2009 Jul 29;10:341. Epub 2009 Jul 29.

UMR M100 Ifremer-Université de Caen Basse-Normandie Physiologie et Ecophysiologie des Mollusques Marins, Centre de Brest, B,P, 70, 29280 Plouzané/IBFA, IFR ICORE 146, Esplanade de la Paix, 14032 Caen Cedex, France.

Background: Although bivalves are among the most-studied marine organisms because of their ecological role and economic importance, very little information is available on the genome sequences of oyster species. This report documents three large-scale cDNA sequencing projects for the Pacific oyster Crassostrea gigas initiated to provide a large number of expressed sequence tags that were subsequently compiled in a publicly accessible database. This resource allowed for the identification of a large number of transcripts and provides valuable information for ongoing investigations of tissue-specific and stimulus-dependant gene expression patterns. These data are crucial for constructing comprehensive DNA microarrays, identifying single nucleotide polymorphisms and microsatellites in coding regions, and for identifying genes when the entire genome sequence of C. gigas becomes available.

Description: In the present paper, we report the production of 40,845 high-quality ESTs that identify 29,745 unique transcribed sequences consisting of 7,940 contigs and 21,805 singletons. All of these new sequences, together with existing public sequence data, have been compiled into a publicly-available Website http://public-contigbrowser.sigenae.org:9090/Crassostrea_gigas/index.html. Approximately 43% of the unique ESTs had significant matches against the SwissProt database and 27% were annotated using Gene Ontology terms. In addition, we identified a total of 208 in silico microsatellites from the ESTs, with 173 having sufficient flanking sequence for primer design. We also identified a total of 7,530 putative in silico, single-nucleotide polymorphisms using existing and newly-generated EST resources for the Pacific oyster.

Conclusion: A publicly-available database has been populated with 29,745 unique sequences for the Pacific oyster Crassostrea gigas. The database provides many tools to search cleaned and assembled ESTs. The user may input and submit several filters, such as protein or nucleotide hits, to select and download relevant elements. This database constitutes one of the most developed genomic resources accessible among Lophotrochozoans, an orphan clade of bilateral animals. These data will accelerate the development of both genomics and genetics in a commercially-important species with the highest annual, commercial production of any aquatic organism.
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http://dx.doi.org/10.1186/1471-2164-10-341DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2907693PMC
July 2009

NMR structure of rALF-Pm3, an anti-lipopolysaccharide factor from shrimp: model of the possible lipid A-binding site.

Biopolymers 2009 Mar;91(3):207-20

CNRS UMR5048, INSERM, U554, Université Montpellier 1 et 2, Centre de Biochimie Structurale, 29 rue de Navacelles, 34090 Montpellier, Cedex 9, France.

The anti-lipopolysaccharide factor ALF-Pm3 is a 98-residue protein identified in hemocytes from the black tiger shrimp Penaeus monodon. It was expressed in Pichia pastoris from the constitutive glyceraldehyde-3-phosphate dehydrogenase promoter as a folded and (15)N uniformly labeled rALF-Pm3 protein. Its 3D structure was established by NMR and consists of three alpha-helices packed against a four-stranded beta-sheet. The C(34)-C(55) disulfide bond was shown to be essential for the structure stability. By using surface plasmon resonance, we demonstrated that rALF-Pm3 binds to LPS, lipid A and to OM-174, a soluble analogue of lipid A. Biophysical studies of rALF-Pm3/LPS and rALF-Pm3/OM-174 complexes indicated rather high molecular sized aggregates, which prevented us to experimentally determine by NMR the binding mode of these lipids to rALF-Pm3. However, on the basis of striking structural similarities to the FhuA/LPS complex, we designed an original model of the possible lipid A-binding site of ALF-Pm3. Such a binding site, located on the ALF-Pm3 beta-sheet and involving seven charged residues, is well conserved in ALF-L from Limulus polyphemus and in ALF-T from Tachypleus tridentatus. In addition, our model is in agreement with experiments showing that beta-hairpin synthetic peptides corresponding to ALF-L beta-sheet bind to LPS. Delineating lipid A-binding site of ALFs will help go further in the de novo design of new antibacterial or LPS-neutralizing drugs.
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http://dx.doi.org/10.1002/bip.21119DOI Listing
March 2009

Oyster hemocytes express a proline-rich peptide displaying synergistic antimicrobial activity with a defensin.

Mol Immunol 2009 Feb 28;46(4):516-22. Epub 2008 Oct 28.

Ifremer, CNRS, Université de Montpellier II, UMR 5119 "Ecosystèmes Lagunaires", Place Eugène Bataillon, CC80, 34095 Montpellier Cedex 5, France.

A cDNA sequence that encodes a 61-amino acid polypeptide precursor with homologies to proline-rich antimicrobial peptides (AMPs) was identified in the oyster Crassostrea gigas. After release of a hydrophobic signal peptide, the resulting 37-amino acid peptide, Cg-Prp, is composed of an acidic region and a cationic proline-rich region. To evaluate the biological properties of Cg-Prp, multiple proline-rich peptides corresponding to putative processing of the full-length Cg-Prp were synthesized. A limited antimicrobial activity was observed for two of them, which also showed strong synergistic antimicrobial activity with Cg-Def, a defensin from C. gigas. To our knowledge, this is the first evidence of synergy between a defensin and another AMP in an invertebrate. By in situ hybridization, the expression of Cg-prp was found to be restricted to hemocytes and induced following bacterial challenge. Cg-prp transcripts were also detected in hemocytes infiltrating mantle, where Cg-Def is expressed. Additionally, by immunocytochemistry, we showed that Cg-Prp or one of its variants is present in some hemocytes together with defensins. In conclusion, we described here the first proline-rich AMP from mollusk. From our study, it is likely to provide a first line of defense against bacterial invasion by acting through synergy with defensins.
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http://dx.doi.org/10.1016/j.molimm.2008.07.021DOI Listing
February 2009

A relationship between antimicrobial peptide gene expression and capacity of a selected shrimp line to survive a Vibrio infection.

Mol Immunol 2008 Jul 19;45(12):3438-45. Epub 2008 May 19.

Ifremer, CNRS, Université de Montpellier II, UMR 5119 Ecosystèmes Lagunaires, Place Eugène Bataillon, CC80, 34095 Montpellier Cedex 5, France.

Understanding of antimicrobial defence mechanisms of penaeid shrimp should help in the design of efficient strategies for the management and disease control in aquaculture. In this study, we have specifically analysed the expression in circulating hemocytes of antimicrobial peptides (AMPs) encoding genes, such as PEN2 and PEN3, ALF, crustin, lysozyme and a putative cysteine-rich peptide. We evidenced a relationship between the level of expression of some AMPs and the successful response of the shrimp, Litopenaeus stylirostris, to circumvent a pathogenic Vibrio penaeicida infection. Additionally, significant differences in some AMP transcript amounts are evidenced between control, non-selected shrimp line and the third generation breeding of shrimp selected for their survival to natural V. penaeicida infections. On the basis of these results, it will now be of great interest to determine if these AMPs are directly involved in the resistance of shrimp to infection or if they only reflect other acquired defence mechanisms which can confer a resistance.
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http://dx.doi.org/10.1016/j.molimm.2008.04.002DOI Listing
July 2008

Rapid accumulation of an interleukin 17 homolog transcript in Crassostrea gigas hemocytes following bacterial exposure.

Dev Comp Immunol 2008 18;32(9):1099-104. Epub 2008 Mar 18.

School of Aquatic and Fisheries Science, University of Washington-Seattle, Box 355020, 1122 NE Boat Street, Seattle, WA 98105, USA.

Interleukin-17 (IL-17) gene models have been found in the sequenced genomes of Strongylocentrotus purpuratus and Caenorhabditis elegans. However, there have been no published reports on the empirical cloning and characterization of any interleukin cDNAs in invertebrates. From a Pacific oyster (Crassostrea gigas) hemocyte cDNA library, two clones were obtained that encoded a protein similar to vertebrate IL-17s. The putative oyster IL-17 homolog (CgIL-17) was 27% identical to rainbow trout IL-17D, 21% to human IL-17D and 24% to an IL-17D-like gene model obtained from the annotation of the sea urchin genome. IL-17s from the oyster, sea urchin, trout and human, contained conserved cysteine residues found in all forms of IL-17 in mammals. Injection of bacteria into C. gigas oysters produced a large and rapid elevation in CgIL-17 transcript abundance in hemocytes, suggesting that this is a very early response gene to pathogens that may be responsible for the stimulation of other immune genes in the oyster.
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http://dx.doi.org/10.1016/j.dci.2008.02.006DOI Listing
July 2008