Extracts from Wallis Sponges Inhibit Vibrio harveyi Biofilm Formation.

Pathogenic bacteria and their biofilms are involved in many human and animal diseases and are a major public health problem with, among other things, the development of antibiotic resistance. These biofilms are known to induce chronic infections for which classical treatments using antibiotic therapy are often ineffective. Sponges are sessile filter-feeding marine organisms known for their dynamic symbiotic partnerships with diverse microorganisms and their production of numerous metabolites of interest. In this study, we investigated the antibiofilm efficacy of different extracts from sponges, isolated in Wallis, without biocidal activity. Out of the 47 tested extracts, from 28 different genera, 11 showed a strong activity against Vibrio harveyi biofilm formation. Moreover, one of these extracts also inhibited two quorum-sensing pathways of V. harveyi.

Impacts of ocean acidification and warming on post-larval growth and metabolism in two populations of the great scallop (Pecten maximus).

Ocean acidification and warming are key stressors for many marine organisms. Some organisms display physiological acclimatization or plasticity, but this may vary across species ranges, especially if populations are adapted to local climatic conditions. Understanding how acclimatization potential varies among populations is therefore important in predicting species responses to climate change. We carried out a common garden experiment to investigate how different populations of the economically important great scallop (Pecten maximus) from France and Norway responded to variation in temperature and PCO2 concentration. After acclimation, post-larval scallops (spat) were reared for 31 days at one of two temperatures (13°C or 19°C) under either ambient or elevated PCO2 (pH 8.0 and pH 7.7). We combined measures of proteomic, metabolic and phenotypic traits to produce an integrative picture of how physiological plasticity varies between the populations. The proteome of French spat showed significant sensitivity to environmental variation, with 12 metabolic, structural and stress-response proteins responding to temperature and/or PCO2. Principal component analysis revealed seven energy metabolism proteins in French spat that were consistent with countering ROS stress under elevated temperature. Oxygen uptake in French spat did not change under elevated temperature but increased under elevated PCO2. In contrast, Norwegian spat reduced oxygen uptake under both elevated temperature and PCO2. Metabolic plasticity allows French scallops to maintain greater energy availability for growth compared with Norwegian spat. However, increased physiological plasticity and growth in French spat may come at a cost, as they showed reduced survival compared with Norwegian scallops under elevated temperature.

The first use of LC-MS/MS proteomic approach in the brown mussel Perna perna after bacterial challenge: Searching for key proteins on immune response.

The brown mussel Perna perna is a valuable fishing resource, primarily in tropical and subtropical coastal regions. Because of their filter-feeding habits, mussels are directly exposed to bacteria in the water column. Escherichia coli (EC) and Salmonella enterica (SE) inhabit human guts and reach the marine environment through anthropogenic sources, such as sewage. Vibrio parahaemolyticus (VP) is indigenous to coastal ecosystems but can be harmful to shellfish. In this study, we aimed to assess the protein profile of the hepatopancreas of P. perna mussel challenged by introduced - E. coli and S. enterica - and indigenous marine bacteria - V. parahaemolyticus. Bacterial-challenge groups were compared with non-injected (NC) and injected control (IC) - that consisted in mussels not challenged and mussels injected with sterile PBS-NaCl, respectively. Through LC-MS/MS proteomic analysis, 3805 proteins were found in the hepatopancreas of P. perna. From the total, 597 were significantly different among conditions. Mussels injected with VP presented 343 proteins downregulated compared with all the other conditions, suggesting that VP suppresses their immune response. Particularly, 31 altered proteins - upregulated or downregulated - for one or more challenge groups (EC, SE, and VP) compared with controls (NC and IC) are discussed in detail in the paper. For the three tested bacteria, significantly different proteins were found to perform critical roles in immune response at all levels, namely: recognition and signal transduction; transcription; RNA processing; translation and protein processing; secretion; and humoral effectors. This is the first shotgun proteomic study in P. perna mussel, therefore providing an overview of the protein profile of the mussel hepatopancreas, focused on the immune response against bacteria. Hence, it is possible to understand the immune-bacteria relationship at molecular levels better. This knowledge can support the development of strategies and tools to be applied to coastal marine resource management and contribute to the sustainability of coastal systems.

Energy metabolism of juvenile scallops Nodipecten subnodosus under acute increased temperature and low oxygen availability.

High temperature increases energy demand in ectotherms, limiting their physiological capability to cope with hypoxic events. The present study aimed to assess the metabolic tolerance of juvenile Nodipecten subnodosus scallops to acute hyperthermia combined with moderate hypoxia. A previous study showed that juveniles exhibited a high upper temperature limit (32 °C), but the responses of juveniles to combined hyperthermia and low dissolved oxygen are unknown. Scallops were exposed to control conditions (treatment C: 22 °C, ∼7.1 mg O2 L-1 or PO2 156.9 mmHg), acute hyperthermia under normoxia (treatment T: 30 °C, ∼6.0 mg O2 L-1 or PO2 150.9 mmHg) or acute hyperthermia plus hypoxia (treatment TH: 30 °C, ∼2.5 mg O2 L-1 or PO2 62.5 mmHg) for 18 h. In T, juveniles exhibited an enhanced oxygen consumption, together with a decrease in adenylate energy charge (AEC) and arginine phosphate (ArgP), and with no changes in metabolic enzyme activity in the muscle. In TH, scallops maintained similar AEC and ArgP levels in muscle as those observed in T treatment. This response occurred along with the accumulation of inosine monophosphate and hypoxanthine. Besides, reduced citrate synthase and pyruvate kinase activities, enhanced hexokinase activity, and a higher octopine dehydrogenase/lactate dehydrogenase ratio in the mantle indicated the onset of anaerobiosis in TH. These responses indicate that juvenile scallops showed tissue-specific compensatory responses regarding their energy balance under moderate hypoxia at high temperatures. Our results give an insight into the tolerance limit of this species to combined hyperthermia and hypoxia in its northern limit of distribution.

Harsh intertidal environment enhances metabolism and immunity in oyster (Crassostrea gigas) spat.

The Pacific oyster Crassostrea gigas is established in the marine intertidal zone, experiencing rapid and highly dynamic environmental changes throughout the tidal cycle. Depending on the bathymetry, oysters face oxygen deprivation, lack of nutrients, and high changes in temperature during alternation of the cycles of emersion/immersion. Here we showed that intertidal oysters at a bathymetry level of 3 and 5 m delayed by ten days the onset of mortality associated with Pacific Oyster Mortality Syndrome (POMS) as compared to subtidal oysters. Intertidal oysters presented a lower growth but similar energetic reserves to subtidal oysters but induced proteomic changes indicative of a boost in metabolism, inflammation, and innate immunity that may have improved their resistance during infection with the Ostreid herpes virus. Our work highlights that intertidal harsh environmental conditions modify host-pathogen interaction and improve oyster health. This study opens new perspectives on oyster farming for mitigation strategies based on tidal height.

Physiological and comparative proteomic analyzes reveal immune defense response of the king scallop Pecten maximus in presence of paralytic shellfish toxin (PST) from Alexandrium minutum.

The king scallop, Pecten maximus is a highly valuable seafood in Europe. Over the last few years, its culture has been threatened by toxic microalgae during harmful algal blooms, inducing public health concerns. Indeed, phycotoxins accumulated in bivalves can be harmful for human, especially paralytic shellfish toxins (PST) synthesized by the microalgae Alexandrium minutum. Deleterious effects of these toxic algae on bivalves have also been reported. However, its impact on bivalves such as king scallop is far from being completely understood. This study combined ecophysiological and proteomic analyzes to investigate the early response of juvenile king scallops to a short term exposure to PST producing A. minutum. Our data showed that all along the 2-days exposure to A. minutum, king scallops exhibited transient lower filtration and respiration rates and accumulated PST. Significant inter-individual variability of toxin accumulation potential was observed among individuals. Furthermore, we found that ingestion of toxic algae, correlated to toxin accumulation was driven by two factors: 1/ the time it takes king scallop to recover from filtration inhibition and starts to filtrate again, 2/ the filtration level to which king scallop starts again to filtrate after inhibition. Furthermore, at the end of the 2-day exposure to A. minutum, proteomic analyzes revealed an increase of the killer cell lectin-like receptor B1, involved in adaptative immune response. Proteins involved in detoxification and in metabolism were found in lower amount in A. minutum exposed king scallops. Proteomic data also showed differential accumulation in several structure proteins such as ß-actin, paramyosin and filamin A, suggesting a remodeling of the mantle tissue when king scallops are subjected to an A. minutum exposure.

Author Correction: Proteinaceous secretion of bioadhesive produced during crawling and settlement of Crassostrea gigas larvae.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

Coupling caging and proteomics on the European flounder (Platichthys flesus) to assess the estuarine water quality at micro scale.

Estuaries are important areas highly vulnerable to anthropogenic pollutions. Therefore, the assessment of estuarine water quality is a major ecological issue. In this study, we sampled juveniles of the European flounder in the "pristine" Canche estuary, and caged them in Canche and in two polluted sites of the Seine estuary, Rouen and Fosse Nord. After one month, the metal and organic pollutants in these sites were assessed, and we evaluated several phenotypic indicators (condition index, RNA/DNA ratios and genotoxicity), and extracted the proteins in fish livers for analysis using a shotgun proteomics approach. The results showed strong modifications in the fish caged in both sites of the Seine estuary, as compared to those caged in Canche. In particular, many proteins involved in phase I and phase II detoxification reactions were accumulated in the liver of fish caged in the site showing the highest pollution, Rouen. In addition, we observed a general disruption of metabolism, in particular an increase in lipid synthesis and carbohydrate degradation in Rouen, and a decrease in the abundance of proteins associated to translational activity in Fosse Nord. At both sites, several stress proteins were decreased. The proteomic impact of the encagement by itself was also evaluated, by comparing the liver proteome of fish caged in Canche to that of fish stayed in natura during the same time. The results showed proteomic signatures of exposure to stressful conditions (particularly heat stress), most probably related to the micro-habitat in which the cages were placed. In conclusion, the caging technique is of great interest for ecotoxicological assessment of estuarine waters, but should consider that the results are representative of the micro-habitat around the cages, which does not necessarily represent the overall heterogeneity of the estuarine environment.

[The oyster Crassostrea gigas, a new model against cancer]. / Crassostrea gigas, une huître au service de la recherche sur le cancer.

The Warburg effect is one of the hallmarks of cancer cells in humans. It is a true metabolic reprogramming to aerobic glycolysis, allowing cancer cells to meet their particular energy needs for growth, proliferation, and resistance to apoptosis, depending on the microenvironment they encounter within the tumor. We have recently discovered that the Crassostrea gigas oyster can naturally reprogram its metabolism to the Warburg effect. Thus, the oyster becomes a new invertebrate model useful for cancer research. Due to its lifestyle, the oyster C. gigas has special abilities to adapt its metabolism to the extreme changes in the environment in which it is located. The oyster C. gigas is therefore a model of interest to study how the environment can control the Warburg effect under conditions that could not be explored in vertebrate model species.

In Silico Analysis of Pacific Oyster (Crassostrea gigas) Transcriptome over Developmental Stages Reveals Candidate Genes for Larval Settlement.

Following their planktonic phase, the larvae of benthic marine organisms must locate a suitable habitat to settle and metamorphose. For oysters, larval adhesion occurs at the pediveliger stage with the secretion of a proteinaceous bioadhesive produced by the foot, a specialized and ephemeral organ. Oyster bioadhesive is highly resistant to proteomic extraction and is only produced in very low quantities, which explains why it has been very little examined in larvae to date. In silico analysis of nucleic acid databases could help to identify genes of interest implicated in settlement. In this work, the publicly available transcriptome of Pacific oyster Crassostrea gigas over its developmental stages was mined to select genes highly expressed at the pediveliger stage. Our analysis revealed 59 sequences potentially implicated in adhesion of C. gigas larvae. Some related proteins contain conserved domains already described in other bioadhesives. We propose a hypothetic composition of C. gigas bioadhesive in which the protein constituent is probably composed of collagen and the von Willebrand Factor domain could play a role in adhesive cohesion. Genes coding for enzymes implicated in DOPA chemistry were also detected, indicating that this modification is also potentially present in the adhesive of pediveliger larvae.

Metal subcellular partitioning determines excretion pathways and sensitivity to cadmium toxicity in two marine fish species.

Subcellular cadmium (Cd) partitioning was investigated in the liver of two marine fish species, the European sea bass Dicentrarchus labrax and the Senegalese sole Solea senegalensis, dietary exposed to an environmentally realistic Cd dose for two months followed by a two-month depuration. The two species displayed different handling strategies during the depuration period. Cd was largely bound to detoxifying fractions such as heat stable proteins (HSP) including metallothioneins (MT) in sea bass, while Cd was more linked to sensitive fractions such as organelles in sole. Whole liver concentrations and subcellular partitioning were also determined for essential elements. The greatest impairment of essential metal homeostasis due to Cd exposure was found in sole. These elements followed the Cd partitioning pattern, suggesting that they are involved in antioxidant responses against Cd toxicity. Cd consumption diminished sole growth in terms of body weight, probably due to lipid storage impairment. The contrasting partitioning patterns showed by the two species might imply different pathways for Cd elimination from the liver. In sea bass, MT-bound Cd would be excreted through bile or released into blood, crossing the cell membrane via a protein transporter. In sole, MRG-bound Cd would be sequestered by organelles before being released into the blood via vesicular exocytosis. These distinct strategies in cellular Cd handling in the liver might account for differential sensitivity to Cd toxicity and differential Cd excretion pathways between the two marine fish species.

Proteinaceous secretion of bioadhesive produced during crawling and settlement of Crassostrea gigas larvae.

Bioadhesion of marine organisms has been intensively studied over the last decade because of their ability to attach in various wet environmental conditions and the potential this offers for biotechnology applications. Many marine mollusc species are characterized by a two-phase life history: pelagic larvae settle prior to metamorphosis to a benthic stage. The oyster Crassostrea gigas has been extensively studied for its economic and ecological importance. However, the bioadhesive produced by ready to settle larvae of this species has been little studied. The pediveliger stage of oysters is characterized by the genesis of a specific organ essential for adhesion, the foot. Our scanning electron microscopy and histology analysis revealed that in C. gigas the adhesive is produced by several foot glands. This adhesive is composed of numerous fibres of differing structure, suggesting differences in chemical composition and function. Fourier transformed infrared spectroscopy indicated a mainly proteinaceous composition. Proteomic analysis of footprints was able to identify 42 proteins, among which, one uncharacterized protein was selected on the basis of its pediveliger transcriptome specificity and then located by mRNA in situ hybridization, revealing its potential role during substrate exploration before oyster larva settlement.

Significance of metallothioneins in differential cadmium accumulation kinetics between two marine fish species.

Impacted marine environments lead to metal accumulation in edible marine fish, ultimately impairing human health. Nevertheless, metal accumulation is highly variable among marine fish species. In addition to ecological features, differences in bioaccumulation can be attributed to species-related physiological processes, which were investigated in two marine fish present in the Canary Current Large Marine Ecosystem (CCLME), where natural and anthropogenic metal exposure occurs. The European sea bass Dicentrarchus labrax and Senegalese sole Solea senegalensis were exposed for two months to two environmentally realistic dietary cadmium (Cd) doses before a depuration period. Organotropism (i.e., Cd repartition between organs) was studied in two storage compartments (the liver and muscle) and in an excretion vector (bile). To better understand the importance of physiological factors, the significance of hepatic metallothionein (MT) concentrations in accumulation and elimination kinetics in the two species was explored. Accumulation was faster in the sea bass muscle and liver, as inferred by earlier Cd increase and a higher accumulation rate. The elimination efficiency was also higher in the sea bass liver compared to sole, as highlighted by greater biliary excretion. In the liver, no induction of MT synthesis was attributed to metal exposure, challenging the relevance of using MT concentration as a biomarker of metal contamination. However, the basal MT pools were always greater in the liver of sea bass than in sole. This species-specific characteristic might have enhanced Cd biliary elimination and relocation to other organs such as muscle through the formation of more Cd/MT complexes. Thus, MT basal concentrations seem to play a key role in the variability observed in terms of metal concentrations in marine fish species.

Evolution of the plasma proteome of divers before and after a single SCUBA dive.

PURPOSE: Decompression sickness (DCS) is a poorly understood and complex systemic disease caused by inadequate desaturation following a reduction of ambient pressure. A previous proteomic study of ours showed that DCS occurrence but not diving was associated with changes in the plasma proteome in rats, including a dramatic decrease of abundance of the tetrameric form of Transthyretin (TTR). The present study aims to assess the impact on the human blood proteome of a dive inducing significant decompression stress but without inducing DCS symptoms. EXPERIMENTAL DESIGN: Twelve healthy male divers were subjected to a single dive at a depth of 18 m of sea water (msw) with a 47-min bottom time followed by a direct ascent to the surface at a rate of 9 msw/min. Venous blood was collected before the dive as well as 30 min and 2 h following the dive. The plasma proteomes from four individuals were then analyzed by using a two-dimensional electrophoresis-based proteomic strategy. RESULTS: No protein spot showed a significantly changed abundance (fdr< 0.1) between the tested times. CONCLUSION: These results strengthen the hypothesis according to which significant changes of the plasma proteome measurable with two-dimensional electrophoresis may only occur along with DCS symptoms.

Dataset of differentially accumulated proteins in Mucor strains representative of four species grown on synthetic potato dextrose agar medium and a cheese mimicking medium.

The data presented are associated with the "Proteomic analysis of the adaptative response of Mucor spp. to cheese environment" (Morin-Sardin et al., 2016) article [1]. Mucor metabolism is poorly documented in the literature and while morphology and growth behavior suggest potential adaptation to cheese for some strains, no adaptation markers to cheese environment have been identified for this genus. To establish the possible existence of metabolic functions related to cheese adaptation, we used a gel based 2-DE proteomic approach coupled to LC-MS/MS to analyze three strains from species known or proposed to have a positive or negative role in cheese production as well as a strain from a non-related cheese-species.

Proteomic responses of European flounder to temperature and hypoxia as interacting stressors: Differential sensitivities of populations.

In the context of global change, ectotherms are increasingly impacted by abiotic perturbations. Along the distribution area of a species, the populations at low latitudes are particularly exposed to temperature increase and hypoxic events. In this study, we have compared the proteomic responses in the liver of European flounder populations, by using 2-D electrophoresis. One southern peripheral population from Portugal vs two northern core populations from France, were reared in a common garden experiment. Most of the proteomic differences were observed between the two experimental conditions, a cold vs a warm and hypoxic conditions. Consistent differentiations between populations were observed in accumulation of proteins involved in the bioenergetics- and methionine-metabolisms, fatty acids transport, and amino-acid catabolism. The specific regulation of crucial enzymes like ATP-synthase and G6PDH, in the liver of the southern population, could be related to a possible local adaptation. This southern peripheral population is spatially distant from northern core populations and has experienced dissimilar ecological conditions; thus it may contain genotypes that confer resilience to climate changes.

Proteomic analysis of the adaptative response of Mucor spp. to cheese environment.

In the cheese industry context, Mucor species exhibit an ambivalent behavior as some species are essential "technological" organisms of some cheeses while others can be spoiling agents. Previously, we observed that cheese "technological" species exhibited higher optimal growth rates on cheese related matrices than on synthetic media. This growth pattern combined with morphological differences raise the question of their adaptation to cheese. In this study, using a comparative proteomic approach, we described the metabolic pathways of three Mucor strains considered as "technological" or "contaminant" in the cheese environment (M. lanceolatus UBOCC-A-109153, M. racemosus UBOCC-A-109155, M. circinelloides CBS 277-49) as well as a non-cheese related strain (M. endophyticus CBS 385-95). Overall, 15.8 to 19.0% of the proteomes showed a fold change ≥1.6 in Potato Dextrose Agar (PDA) versus Cheese Agar (CA), a cheese mimicking-medium. The 289 differentially expressed proteins identified by LC MS-MS analysis were mostly assigned to energy and amino-acid metabolisms in PDA whereas a higher diversity of biological processes was observed for cheese related strains in CA. Surprisingly, the vast majority (72.9%) of the over-accumulated proteins were different according to the considered medium and strain. These results strongly suggest that the observed better adaptative response of "technological" strains to cheese environment is mediated by species-specific proteins. BIOLOGICAL SIGNIFICANCE: The Mucor genus consists of a multitude of poorly known species. In the food context, few species are known for their positive role in the production of various food products, including cheese, while others are spoiling agents. The present study focused on the analysis of morphological and proteome differences of various Mucor spp. representative strains known as either positively (hereafter referred as "technological") or negatively (hereafter referred as "contaminant") associated with cheese or non-related to cheese (endophyte) on two different media, a synthetic medium and a cheese-mimicking medium. The main goal was to assess if adaptative traits of "technological" strains to the cheese environment could be identified. This work was based on observations we did in a recently published physiological study (Morin-Sardin et al., 2016). One of the important innovative aspects lies in the use for the first time of an extensive 2-DE approach to compare proteome variations for 4 strains on two different media. Results obtained offered an insight in the metabolic mechanisms associated with growth on a given medium and showed that adaptation to cheese environment is probably supported by species-specific proteins. The obtained data represent an essential step point for more targeted studies at the genomic and transcriptomic levels.

Effect of simulated air dive and decompression sickness on the plasma proteome of rats.

PURPOSE: Decompression sickness (DCS) is a poorly understood systemic disease caused by inadequate desaturation following a reduction in ambient pressure. Although recent studies highlight the importance of circulating factors, the available data are still puzzling. In this study, we aimed to identify proteins and biological pathways involved in the development of DCS in rats. EXPERIMENTAL DESIGN: Eighteen male Sprague-Dawley rats were subjected to a same simulated air dive to 1000 kPa absolute pressure and divided into two groups: no DCS or DCS. A third control group remained at atmospheric pressure. Venous blood was collected after hyperbaric exposure and the plasma proteomes from four individuals per group were analyzed by using a two-dimensional electrophoresis-based proteomic strategy. RESULTS: Quantitative analysis identified nine protein spots with abundances significantly changed (false discovery rate < 0.1) between the tested conditions. Three protein spots, identified as Apolipoprotein A1, Serine Protease Inhibitor A3K (Serpin A3K), and Alpha-1-antiproteinase, appeared increased in DCS animals but displayed only weak changes. By contrast, one protein spot identified as Transthyretin (TTR) dramatically decreased (i.e. quite disappeared) in animals displaying DCS symptoms. Before diving, TTR level was not different in DCS than nondiving group. CONCLUSION: These results may lead to the use of TTR as an early biomarker of DCS.

Non-additive effects of ocean acidification in combination with warming on the larval proteome of the Pacific oyster, Crassostrea gigas.

UNLABELLED: Increasing atmospheric carbon dioxide results in ocean acidification and warming, significantly impacting marine invertebrate larvae development. We investigated how ocean acidification in combination with warming affected D-veliger larvae of the Pacific oyster Crassostrea gigas. Larvae were reared for 40h under either control (pH8.1, 20 °C), acidified (pH7.9, 20 °C), warm (pH8.1, 22 °C) or warm acidified (pH7.9, 22 °C) conditions. Larvae in acidified conditions were significantly smaller than in the control, but warm acidified conditions mitigated negative effects on size, and increased calcification. A proteomic approach employing two-dimensional electrophoresis (2-DE) was used to quantify proteins and relate their abundance to phenotypic traits. In total 12 differentially abundant spots were identified by nano-liquid chromatography-tandem mass spectrometry. These proteins had roles in metabolism, intra- and extra-cellular matrix formations, stress response, and as molecular chaperones. Seven spots responded to reduced pH, four to increased temperature, and six to acidification and warming. Reduced abundance of proteins such as ATP synthase and GAPDH, and increased abundance of superoxide dismutase, occurred when both pH and temperature changes were imposed, suggesting altered metabolism and enhanced oxidative stress. These results identify key proteins that may be involved in the acclimation of C. gigas larvae to ocean acidification and warming. SIGNIFICANCE: Increasing atmospheric CO2 raises sea surface temperatures and results in ocean acidification, two climatic variables known to impact marine organisms. Larvae of calcifying species may be particularly at risk to such changing environmental conditions. The Pacific oyster Crassostrea gigas is ecologically and commercially important, and understanding its ability to acclimate to climate change will help to predict how aquaculture of this species is likely to be impacted. Modest, yet realistic changes in pH and/or temperature may be more informative of how populations will respond to contemporary climate change. We showed that concurrent acidification and warming mitigates the negative effects of pH alone on size of larvae, but proteomic analysis reveals altered patterns of metabolism and an increase in oxidative stress suggesting non-additive effects of the interaction between pH and temperature on protein abundance. Thus, even small changes in climate may influence development, with potential consequences later in life.

Deciphering the molecular adaptation of the king scallop (Pecten maximus) to heat stress using transcriptomics and proteomics.

BACKGROUND: The capacity of marine species to survive chronic heat stress underpins their ability to survive warming oceans as a result of climate change. In this study RNA-Seq and 2-DE proteomics were employed to decipher the molecular response of the sub-tidal bivalve Pecten maximus, to elevated temperatures. RESULTS: Individuals were maintained at three different temperatures (15, 21 and 25 °C) for 56 days, representing control conditions, maximum environmental temperature and extreme warming, with individuals sampled at seven time points. The scallops thrived at 21 °C, but suffered a reduction in condition at 25 °C. RNA-Seq analyses produced 26,064 assembled contigs, of which 531 were differentially expressed, with putative annotation assigned to 177 transcripts. The proteomic approach identified 24 differentially expressed proteins, with nine identified by mass spectrometry. Network analysis of these results indicated a pivotal role for GAPDH and AP-1 signalling pathways. Data also suggested a remodelling of the cell structure, as revealed by the differential expression of genes involved in the cytoskeleton and cell membrane and a reduction in DNA repair. They also indicated the diversion of energetic metabolism towards the mobilization of lipid energy reserves to fuel the increased metabolic rate at the higher temperature. CONCLUSIONS: This work provides preliminary insights into the response of P. maximus to chronic heat stress and provides a basis for future studies examining the tipping points and energetic trade-offs of scallop culture in warming oceans.