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M.S. Clark et al.
whatever measure is taken, is a snapshot at that particular point in time and reflects
a particular set of environmental variables. Interpretation of such data does require
an extensive background knowledge of the organism. For example events such as
spawning or the effects of seasonal temperature variations (thermal history) and production of season-specific proteins (cf. antifreezes in winter) (Buckley et al. 2001,
Tomanek 2002, Enevoldsen et al. 2003, Jin and DeVries 2006) can significantly
alter gene expression patterns and will obviously bias any profiling work. This variation in gene expression according to organism history and environmental signals is
termed plasticity and represents a range or expression window in which genes (and
as a consequence species) can operate effectively and adapt.
This is another area where studies are largely confined to the individual gene level
and even so, such data is limited, but it is emerging that this plasticity of response
is highly gene dependant. In a comprehensive molecular study into how thermal
history influences muscle development in fish, two temperature responsive genes
were identified; Myogenin and FoxK1 (Fernandes et al. 2006, 2007), but at least
an equal number of genes studied were unaffected by heat treatment (Mackenzie
2006). Most of the work on plasticity, to date, has concentrated on terrestrial species,
as these generally experience far wider temperature ranges than marine species
(cf. Deere and Chown 2006) or the standard model eukaryote, yeast (Stern et al.
2007). But, given predicted increased seawater temperatures under climate change
senarios, this is clearly an emerging area of importance in the marine domain (Peck
et al. 2009). This understanding of which genes are more “adaptable” will progress
as analyses are scaled up to the genomic level using gene chips and new sequencing
technologies.
3.4.4 Adaptation to Extreme Environments
The section on Population Genomics has presented several examples of where DNA
polymorphisms effect gene expression (Section 3.3.4) and hence imply adaptation and specialisation. However, nowhere is adaptation observed as strongly, as
in extreme environments. These require far more large-scale genomic changes to
adapt to what is often a very hostile environment. This is an area, not just of academic inquiry, but also of potential commercial interest, with investigations ranging
from characterisation of novel proteins to identifying enzyme variants that work
“better” under different circumstances that could be used in, for example, food processing or detergent production (Clark et al. 2004, Peck et al. 2005). Whilst many
types of extreme environments exist, this section will concentrate on adaptations to
two of the most commonly described natural environments: hydrothermal vents and
the Polar regions. The aim is to provide an overview of research into two opposite
extremes: the hot and the cold, followed by the relatively “new” challenge of anthropomorphic change (toxicology/pollution). Adaptations to hydrothermal vents and
the Polar regions have taken place over thousands/millions of years, whilst organisms have had to adjust/adapt to pollutants over periods of only tens to hundreds of
years.
M.S. Clark et al.
whatever measure is taken, is a snapshot at that particular point in time and reflects
a particular set of environmental variables. Interpretation of such data does require
an extensive background knowledge of the organism. For example events such as
spawning or the effects of seasonal temperature variations (thermal history) and production of season-specific proteins (cf. antifreezes in winter) (Buckley et al. 2001,
Tomanek 2002, Enevoldsen et al. 2003, Jin and DeVries 2006) can significantly
alter gene expression patterns and will obviously bias any profiling work. This variation in gene expression according to organism history and environmental signals is
termed plasticity and represents a range or expression window in which genes (and
as a consequence species) can operate effectively and adapt.
This is another area where studies are largely confined to the individual gene level
and even so, such data is limited, but it is emerging that this plasticity of response
is highly gene dependant. In a comprehensive molecular study into how thermal
history influences muscle development in fish, two temperature responsive genes
were identified; Myogenin and FoxK1 (Fernandes et al. 2006, 2007), but at least
an equal number of genes studied were unaffected by heat treatment (Mackenzie
2006). Most of the work on plasticity, to date, has concentrated on terrestrial species,
as these generally experience far wider temperature ranges than marine species
(cf. Deere and Chown 2006) or the standard model eukaryote, yeast (Stern et al.
2007). But, given predicted increased seawater temperatures under climate change
senarios, this is clearly an emerging area of importance in the marine domain (Peck
et al. 2009). This understanding of which genes are more “adaptable” will progress
as analyses are scaled up to the genomic level using gene chips and new sequencing
technologies.
3.4.4 Adaptation to Extreme Environments
The section on Population Genomics has presented several examples of where DNA
polymorphisms effect gene expression (Section 3.3.4) and hence imply adaptation and specialisation. However, nowhere is adaptation observed as strongly, as
in extreme environments. These require far more large-scale genomic changes to
adapt to what is often a very hostile environment. This is an area, not just of academic inquiry, but also of potential commercial interest, with investigations ranging
from characterisation of novel proteins to identifying enzyme variants that work
“better” under different circumstances that could be used in, for example, food processing or detergent production (Clark et al. 2004, Peck et al. 2005). Whilst many
types of extreme environments exist, this section will concentrate on adaptations to
two of the most commonly described natural environments: hydrothermal vents and
the Polar regions. The aim is to provide an overview of research into two opposite
extremes: the hot and the cold, followed by the relatively “new” challenge of anthropomorphic change (toxicology/pollution). Adaptations to hydrothermal vents and
the Polar regions have taken place over thousands/millions of years, whilst organisms have had to adjust/adapt to pollutants over periods of only tens to hundreds of
years.