IHPE – Transversal Holobiont

TRANSVERSAL CHALLENGE
« Dynamics of the holobiont and fitness »
Head Eve TOULZA & Caroline MONTAGNANI

Abstract
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ABSTRACT
The concept of holobiont has extended our vision of organisms to the whole (microbial) community living in association with them. These metaorganisms, considered as communities of species, would thus be the true unit of evolution. In this context, the hologenome is defıned as the sum of the genetic information of the host and its symbiotic microorganisms. The hologenome theory of evolution proposes that the object of natural selection is not the individual organism, but the holobiont, i.e. the organism together with its associated microbial communities.
This concept has gained more and more attention for many issues on the functioning, homeostasis or evolution of living organisms. These questions, however, remain open in many taxonomic groups. The goal of this research axis, is to develop collaborative projects to study the extent of these concepts in different model species. The various invertebrates studied in the IHPE laboratory indeed give us today the unique opportunity to explore the impact of the nature and dynamics of the microbiota on their health status and survival as well as their adaptive capabilities (defense against parasites or opportunistic pathogens, resistance to environmental variations).
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The concept of holobiont has extended the notion of organism to all internal and surface microbial communities associated with it. These organisms would then be considered as communities of species, metaorganisms that would be the true unity of evolution resulting from the interaction of their own genome with that of their microbiota. Thus, the hologenome theory defined for the first time in corals by Eugene Rosenberg, considers the holobiont and its hologenome (all interacting genomic entities) as the target of natural selection.
The significance of this concept has become more and more important as the studies showing the impact of the microbial compartment on the fitness of the host and its role in many physiological functions, from reproduction to development, operation of epithelial barriers, immunity, etc. have accumulated. Disruptions of this association could affect the adaptive capabilities and therefore the fitness of the species assemblage.
Another new interesting aspect highlighted by this theory is that of the interaction between a slow evolving macroorganism and a labile microbial community that can change and adapt quickly (microbiota) and from new selective traits may emerge thus influencing the adaptability of this species. In stressful environmental conditions, the symbiotic community can change quickly and this plasticity may play an important role both in the acclimatization and evolution of organisms.
This concept has gained more and more attention for many issues on the functioning, homeostasis or evolution of living organisms. These questions, however, remain open in many taxonomic groups. The goal of this research axis, is to develop collaborative projects to study the extent of these concepts in different model species. The various invertebrates studied in the IHPE laboratory indeed give us the opportunity today to explore the impact of the nature and dynamics of the microbiota on their health status and survival as well as their adaptive capabilities (defense against parasites or opportunistic pathogens, resistance to environmental variations).
In most of these models, it will be necessary to first carry out an inventory of species composing the microbiota, characterize their specificity, and determine their stability over generations. We would then discuss their dynamics in response to environmental stresses, biotic or abiotic. Integrative approaches associating field sampling, controlled environment experiments and high-throughput molecular analysis methods, both at the taxonomic and functional levels (barcoding, metagenomics metatranscriptomics) should allow us to determine the importance of the microbiota in the functioning of these interactions in the light of major ecological crises affecting recurrently some of our models of interest facing global changes.
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FIGURES
HOLOBIONTE-fig1
Holobiont exploration in IHPE invertebrate models (c)IHPE-Montagnani-Toulza-2015
 HOLOBIONTE-fig2
A metagenome (c)http:/armbrustlab.ocean.washington.eduseastar
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CONTACTS
Eve TOULZA (2EIHP team), eve.toulza@univ-perp.fr
Caroline MONTAGNANI (MIMM team), cmontan@ifremer.fr