Study of Diseases and the Immune System of Bivalves Using Molecular Biology and Genomics

Abstract

Environmental chemico-physical factors, pathogens, and biological interactions constantly affect organism physiology and behavior. Invertebrates, including bivalve mollusks do not possess acquired immunity. Their defense mechanisms rely on an innate, non-adaptive immune system employing circulating cells and a large variety of molecular effectors. The mechanisms underlying host defense depend on the presence of functional proteins in appropriate quantities, within a crucial time window. These proteins are encoded by genes whose transcription is tightly coordinated by complex programs of gene expression. Currently available advanced techniques allow the evaluation of this gene expression, expanding our understanding of the behavior and function of cells and tissues under varying conditions. In particular, DNA microarray technology enables measurement of a large predetermined set of known genes or sequences. Expressed sequence tag sequencing from redundant, normalized, subtractive hybridization libraries is a robust method for sampling the protein encoding genes that are expressed within a tissue. The elimination of microorganisms by defense cells is a dynamic process that involves integrating synthesis of granule proteins during differentiation, migration onto sites of infection, phagocytosis and killing of microorganisms, modulation of their effector cells, and finally apoptosis. Understanding how this complex biological process is regulated can best be addressed using a systems biology approach to the study of organisms and populations in order to more effectively decipher the continuous challenge between two genomes, i.e., evolving host-pathogen interactions.

Keywords:

• bivalve
• diseases
• contaminants
• stress
• immune defense
• gene expression
• genomic approach

ACKNOWLEDGMENTS

This work has been carried out within the project “AQUAFUNC” (EU-SSA-022685), with financial support from the Commission of the European Communities. Philippe Roch (Centre National de la Recherche Scientique, CNRS) was partially supported by the Université de Montpellier 2 and the Institut Français pour la Recherche et l'Exploitation de la Mer (IFREMER). Paola Venier acknowledges FOOD-CT-2005-007103 funding and, in part, the Co.Ri.La. Research programme 2004-06. B. Novoa and A. Figueras acknowledge funding from an EC project UE (022685) and from EU Integrated Project FOOD-CT-2005-007103, project AGL2003-02454 from the Ministerio de Ciencia y Tecnología (Spain), project PGIDIT06PXIC402124A4, funded by the Xunta de Galicia. C. Gestal thanks the Spanish Ministerio de Educación y Ciencia for her post-doctoral Ramon y Cajal contract. This review was prepared in the context of the EU project Aquafunc.