7 Genomic Approaches in Aquaculture and Fisheries
249
unravel useful information suitable to develop appropriate solutions. EST projects
can result not only in gene annotation, but also in the establishment of physical
linkage and comparative mapping, analysis of alternative splicing and gene duplication, and microarray development. The development of cDNA microarrays covering
genes from C. gigas and C. virginica exposed to Perkinsus and Vibrio allowed
the characterization of differentially expressed genes in a host-pathogen condition
(Jenny et al. 2006). Also within the framework of the MGE network, microarrays containing genes from oysters (C. gigas), mussels (Mytilus spp.) and clams
(Ruditapes spp.) are being developed.
In parallel, subtractive libraries provide some highly relevant information about
genes differentially expressed during host-parasite interactions. This technique
(Diatchenko et al. 1999) offers a powerful and reliable evaluation of both sides
in the pathogenic interaction, allowing a meticulous characterization of gene regulation either in the host or in the parasite. With the help of this technique, it has
been possible to identify sets of genes differentially expressed in clams exposed to
Vibrio (Gestal et al. 2007), in oysters exposed to Perkinsus (Tanguy et al. 2004) and
Vibrio (Jenny et al. 2006), and in Perkinsus exposed to clam hemocytes (Ascenso
et al. 2007). In addition to the techniques described above, which allow the gathering of consistent and abundant information on the characterization of host/parasite
transcriptomes, many other reliable tools may be accessed, such as pyrosequencing,
SAGE and MPSS, providing strong prospects in a near future.
7.6.4.6 Conclusions
Genomics, in combination with other techniques, can provide powerful approaches
and tools towards the understanding of host-parasite interactions and the control of diseases affecting bivalves. In addition to strain selection programs based
on host molecular markers, e.g. Pacific oyster selection programs to produce
Haplosporidium nelsoni resistant strains (Ford and Haskin 1987), there is currently
a worldwide effort towards the sequencing of host and pathogen genomes to understand defense and infection mechanisms, respectively. Even though important tools,
such as bivalve cell systems, massive high-throughput genomics and microarray
technology, are still missing, available data already provide important clues towards
the understanding of the immune system and physiological processes related to host
defense.
7.7 Genomic Variation, Stock Structure, Adaptation
and Traceability in Natural Fish Populations
7.7.1 The Major Issues
The diversity, structure, evolution and functioning of marine populations is determined by the environment in which they live and their individual biological characteristics. The oceanic environment is characterised by its three dimensions, spatial
continuity throughout a high-density medium and relatively moderate variation of
249
unravel useful information suitable to develop appropriate solutions. EST projects
can result not only in gene annotation, but also in the establishment of physical
linkage and comparative mapping, analysis of alternative splicing and gene duplication, and microarray development. The development of cDNA microarrays covering
genes from C. gigas and C. virginica exposed to Perkinsus and Vibrio allowed
the characterization of differentially expressed genes in a host-pathogen condition
(Jenny et al. 2006). Also within the framework of the MGE network, microarrays containing genes from oysters (C. gigas), mussels (Mytilus spp.) and clams
(Ruditapes spp.) are being developed.
In parallel, subtractive libraries provide some highly relevant information about
genes differentially expressed during host-parasite interactions. This technique
(Diatchenko et al. 1999) offers a powerful and reliable evaluation of both sides
in the pathogenic interaction, allowing a meticulous characterization of gene regulation either in the host or in the parasite. With the help of this technique, it has
been possible to identify sets of genes differentially expressed in clams exposed to
Vibrio (Gestal et al. 2007), in oysters exposed to Perkinsus (Tanguy et al. 2004) and
Vibrio (Jenny et al. 2006), and in Perkinsus exposed to clam hemocytes (Ascenso
et al. 2007). In addition to the techniques described above, which allow the gathering of consistent and abundant information on the characterization of host/parasite
transcriptomes, many other reliable tools may be accessed, such as pyrosequencing,
SAGE and MPSS, providing strong prospects in a near future.
7.6.4.6 Conclusions
Genomics, in combination with other techniques, can provide powerful approaches
and tools towards the understanding of host-parasite interactions and the control of diseases affecting bivalves. In addition to strain selection programs based
on host molecular markers, e.g. Pacific oyster selection programs to produce
Haplosporidium nelsoni resistant strains (Ford and Haskin 1987), there is currently
a worldwide effort towards the sequencing of host and pathogen genomes to understand defense and infection mechanisms, respectively. Even though important tools,
such as bivalve cell systems, massive high-throughput genomics and microarray
technology, are still missing, available data already provide important clues towards
the understanding of the immune system and physiological processes related to host
defense.
7.7 Genomic Variation, Stock Structure, Adaptation
and Traceability in Natural Fish Populations
7.7.1 The Major Issues
The diversity, structure, evolution and functioning of marine populations is determined by the environment in which they live and their individual biological characteristics. The oceanic environment is characterised by its three dimensions, spatial
continuity throughout a high-density medium and relatively moderate variation of