The mussel Bathymodiolus azoricus as a model to study inflammation and innate immune responses in deep-sea vent animals

With the aim of understanding innate immunity, in animals physiologically programed to endure deep-sea vent conditions, we carried out a series of experiments to elucidate the mechanisms underlying responses to infections, wound and long-term acclimatization, in the vent mussel Bathymodiolus azoricus. Evolutionary conserved invertebrate factors were characterized, including phagocytosis, signaling reactions and immune gene expression profiling. Additionally, a full transcriptome sequence analysis, from vent mussel gill tissues, was performed, prompting the identification of a large numbers of novel sequences from both the mussel transcriptome and the metatranscriptome from its associated microbial community in gill tissues. Results from the transcriptome pointed at the presence an unprecedented number of putative immune-related genes which may fall into one the immune recognition, signal transduction, transcription or effector molecule, functional categories. Their physical counterpart was confirmed by semi-quantitative Reverse Transcription-PCR, and quantitative PCR, setting thus the grounds, for more in-depth studies that revealed distinct gene expression profiles showing a great potential to address unique molecular relationships under which the regulation of gene transcription may be affected by environmental factors, including microbes and by the presence of endosymbiont bacteria. Along with this, we set out to investigate the intrinsic modulation of gene expression in B. azoricus, in the presence of their endosymbiont bacteria, in ex-vivo incubation experiments, using gill tissue segments. Experiments indicated that ex-vivo exposure to endosymbiont bacteria have comparable effect on the expression of immune genes, as in control experiments performed with sea water, provided that hemolymph is present in the incubations, whereas Vibrio bacteria have noticeably an up-regulation effect on the same immune genes and this up-regulation effect appeared to be also mediated by humoral factors present in the hemolymph. The newly discovered, transcriptome-derived genes were also studied in live animals and their expression compared in responses to Vibrio infections, wound reactions and hyperbaric stimulations. Results indicated that immune genes are differentially expressed, corroborating evidence supporting immune discriminatory recognition capacities in the deep-sea vent mussels, in view of infections with different Vibrio strains. Furthermore, several analyses demonstrated that immune genes, as well as infections, clustered in discrete groups in accordance with the patterns observed in gene expression changes induced by bacterial pathogens. Our analyses also showed that genes encoding putative immune recognition and signaling molecules corresponded to the most noticeable examples in their comparison of differential gene expression results, supporting thus in vitro experimental systems to study distinct gene expression profiles and bringing further evidence supporting the role of gills as a bona fide immune responsive tissue. Interestingly, cross-talk between signaling pathways may occur in Bathymodiolus azoricus individuals subjected to Vibrio infections, wound responses, and hyperbaric stimulations, i.e. same immune or pro-inflammatory signaling molecules may serve different signaling pathways whether they are conspicuously more expressed or not during such experiments. Cleary, the activation of signaling pathways involved in Vibrio infections was distinct from that of wound and hyperbaric reactions and thus conferring the animal model presented here with the physiological versatility to cope with deep-sea hydrothermal vent environments.

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First Name: 
Raul
Last Name: 
Bettencourt
Telephone: 
+351292200449
Affiliation: 
IMAR-Center, University of the Azores, Portugal
First Name: 
Inês
Last Name: 
Barros
Affiliation: 
IMAR-Center, University of the Azores, Portugal
First Name: 
Eva
Last Name: 
Martins
Affiliation: 
IMAR-Center, University of the Azores, Portugal
First Name: 
Teresa
Last Name: 
Cerqueira
Affiliation: 
IMAR-Center, University of the Azores, Portugal
First Name: 
Inês
Last Name: 
Martins
Affiliation: 
IMAR-Center, University of the Azores, Portugal
First Name: 
Ricardo
Last Name: 
Santos
Affiliation: 
Department of Oceanography and Fisheries, University of the Azores, Portugal
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Ecological Interactions
Physiology
Microbiology
Abstract ID: 
CBE5-184
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