Transcriptomic analysis of the control of chemosynthetic symbionts in Bathymodiolus thermophilus in natural and experimental populations

Deep-sea bathymodiolin mussels harbor chemosynthetic endosymbiotic bacteria in their gills. Bathymodiolus thermophilus, the species that colonize hydrothermal vents of the East Pacific Rise (EPR), harbor a single thiotrophic symbiont that accounts for a large part of the metabolic requirements of the symbiosis. Previous studies have aimed to characterize this symbiosis in term of symbiont phylogeny, tissue localization, and global metabolism but so far only a few studies have been dedicated to identify the molecular mechanisms involved in the maintenance of the symbiotic relationship by the host. In this study we applied transcriptomic approaches to investigate the specific genes and/or metabolic networks involved in the maintenance of the symbiosis in relation to symbiont contents in field population of B. thermophilus but also in experimental populations using mussels placed in cages and translocated in sulfur-free areas followed by a re-exposure to diffuse venting in their original mussel bed. We identified complex patterns of genes showing a regulation in their expression in relation to their symbiont content and/or the depuration effect associated to the lack of sulfide. Genes whose expression was positively correlated to symbiont content included a number of membrane-associated proteins, adhesion proteins, and interestingly, a important number of recognition proteins and apoptotic factors. We showed that the pattern of apoptosis in the gills differed between mussels relative to their symbiont content. Apoptosis in gills of mussels with highest and lowest symbiont content was then checked by TUNEL positive staining. In musssels with high symbiont content, we noticed numerous apoptotic cells compared to mussels harboring a low symbiont content. To validate our results, the expression of several genes involved in the stimulation or inhibition of apoptosis including antiapoptotic proteins such as Bcl2, Necrosis factor kappa B, Defender against apoptotic cell death and inhibitor of apoptosis protein (IAP), were analyzed by Real Time PCR. Our preliminary results suggest that mussel hosts might actively control their bacterial symbiont population through apoptotic processes.

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First Name: 
Hayat
Last Name: 
GUEZI
Telephone: 
00336 35 11 21 08
Affiliation: 
CNRS, UMR 7144, Adaptation et Diversité en Milieu Marin, Station Biologique de Roscoff, 29682 Roscoff, France/ UPMC Université Paris 06, Station Biologique de Roscoff, 29682 Roscoff, France
First Name: 
Arnaud
Last Name: 
TANGUY
Affiliation: 
CNRS, UMR 7144, Adaptation et Diversité en Milieu Marin, Station Biologique de Roscoff, 29682 Roscoff, France/ UPMC Université Paris 06, Station Biologique de Roscoff, 29682 Roscoff, France
First Name: 
Isabelle
Last Name: 
BOUTET
Affiliation: 
CNRS, UMR 7144, Adaptation et Diversité en Milieu Marin, Station Biologique de Roscoff, 29682 Roscoff, France/ UPMC Université Paris 06, Station Biologique de Roscoff, 29682 Roscoff, France
First Name: 
Eiichi
Last Name: 
Shoguchi
Affiliation: 
Okinawa Institute of Science and Technology Promotion Corporation (OIST), 1919-1, Tancha, Onna-Son, Kunigami, Okinawa 904-0412, Japan
First Name: 
Noriyuki
Last Name: 
SATOH
Affiliation: 
Okinawa Institute of Science and Technology Promotion Corporation (OIST), 1919-1, Tancha, Onna-Son, Kunigami, Okinawa 904-0412, Japan
First Name: 
François Henry
Last Name: 
LALLIER
Affiliation: 
CNRS, UMR 7144, Adaptation et Diversité en Milieu Marin, Station Biologique de Roscoff, 29680 Roscoff, France / UPMC Université Paris 06, Station Biologique de Roscoff, 29680 Roscoff, France
Choose keywords that are most applicable to your abstract. (Three maximum.): 
Distribution and abundance
Trophic relations (including symbiosis)
Abstract ID: 
CBE5-159