6 Genomics of Marine Algae
197
O. tauri is also being used as a model organism in the laboratory, allowing experimental investigation of prasinophyte biology in much the same way as
P. tricornutum is being used to study diatoms. O. tauri is attractive as a model
organism for several reasons. One of the most important of these is the simplicity of the O. tauri genome, in particular the fact that most genes are unique and
not part of redundant gene families. In this respect, O. tauri differs from more classical, land plant models such as Arabidopsis and, as a result, is attracting interest
as a system to investigate cellular processes of general relevance to the green lineage. Two other advantageous features are the short intergenic regions, which allow
promoter regions to be easily isolated and studied, and the fact that cell populations are haploid. This latter feature is a potential advantage for genetic approaches,
although at present it is not possible to go through the sexual cycle in the laboratory.
Several tools have been developed for O. tauri including clonal isolation of colonies
on plates, genetic transformation with reporter gene constructs, gene expression
monitoring under defined growth conditions and genome-scale microarray analysis.
These tools are currently being applied to understanding the relationship between
the mitotic cell cycle and the control of circadian rhythms in this alga (Moulager
et al. 2007).
As with the diatoms, therefore, there is extensive genome sequence information
available for the prasinophytes and a powerful model organism that with allow postgenomic analysis of gene function. Additional genome data will be available shortly
for a broad range of prasinophytes (Table 6.1) that have been isolated from diverse
environments (Rodríguez et al. 2005, Slapeta et al. 2006) and comparisons of these
genomes will provide new hypotheses for future investigations both in the field and
in the laboratory.
6.4.5.3 Other Microalgal Genome Projects
Coccolithophores are unicellular, haptophyte algae that tend to be found in nutrientpoor regions of the oceans. They can form large blooms that are seen as patches
of turquoise due to the reflection of light from the calcium carbonate coccoliths
that protect the outsides of the cells. These abundant organisms play an important
role in biogeochemical cycles, particularly in trapping carbon via the sinking of
cellular debris to ocean floor sediments following death. The genome of the coccolithophore Emiliania huxleyi has been sequenced (Table 6.1) and is currently being
analysed with the aim of improving our understanding of many features of the biology of these ecologically important organisms. Genome sequencing projects are also
planned for two species of haptophyte algae from the genus Phaeocystis (Table 6.1)
and EST sequences are also available for Prymnesium parvum (La Claire 2006).
Several recently initiated genome projects target key organisms from the various
groups that have been involved in primary or secondary plastid endosymbiosis events (Fig. 6.1), and a wealth of new information about these events will
soon be available. The glaucophytes are not marine algae but the current genome
project for one member of this group, Cyanophora paradoxa (http://www.biology.
uiowa.edu/cyanophora/cyanophora_home.htm), will constitute an important part
197
O. tauri is also being used as a model organism in the laboratory, allowing experimental investigation of prasinophyte biology in much the same way as
P. tricornutum is being used to study diatoms. O. tauri is attractive as a model
organism for several reasons. One of the most important of these is the simplicity of the O. tauri genome, in particular the fact that most genes are unique and
not part of redundant gene families. In this respect, O. tauri differs from more classical, land plant models such as Arabidopsis and, as a result, is attracting interest
as a system to investigate cellular processes of general relevance to the green lineage. Two other advantageous features are the short intergenic regions, which allow
promoter regions to be easily isolated and studied, and the fact that cell populations are haploid. This latter feature is a potential advantage for genetic approaches,
although at present it is not possible to go through the sexual cycle in the laboratory.
Several tools have been developed for O. tauri including clonal isolation of colonies
on plates, genetic transformation with reporter gene constructs, gene expression
monitoring under defined growth conditions and genome-scale microarray analysis.
These tools are currently being applied to understanding the relationship between
the mitotic cell cycle and the control of circadian rhythms in this alga (Moulager
et al. 2007).
As with the diatoms, therefore, there is extensive genome sequence information
available for the prasinophytes and a powerful model organism that with allow postgenomic analysis of gene function. Additional genome data will be available shortly
for a broad range of prasinophytes (Table 6.1) that have been isolated from diverse
environments (Rodríguez et al. 2005, Slapeta et al. 2006) and comparisons of these
genomes will provide new hypotheses for future investigations both in the field and
in the laboratory.
6.4.5.3 Other Microalgal Genome Projects
Coccolithophores are unicellular, haptophyte algae that tend to be found in nutrientpoor regions of the oceans. They can form large blooms that are seen as patches
of turquoise due to the reflection of light from the calcium carbonate coccoliths
that protect the outsides of the cells. These abundant organisms play an important
role in biogeochemical cycles, particularly in trapping carbon via the sinking of
cellular debris to ocean floor sediments following death. The genome of the coccolithophore Emiliania huxleyi has been sequenced (Table 6.1) and is currently being
analysed with the aim of improving our understanding of many features of the biology of these ecologically important organisms. Genome sequencing projects are also
planned for two species of haptophyte algae from the genus Phaeocystis (Table 6.1)
and EST sequences are also available for Prymnesium parvum (La Claire 2006).
Several recently initiated genome projects target key organisms from the various
groups that have been involved in primary or secondary plastid endosymbiosis events (Fig. 6.1), and a wealth of new information about these events will
soon be available. The glaucophytes are not marine algae but the current genome
project for one member of this group, Cyanophora paradoxa (http://www.biology.
uiowa.edu/cyanophora/cyanophora_home.htm), will constitute an important part