Red algae in general are interesting to industrials as a source of polysaccharides (large molecules, see web site: http://www.sb-roscoff.fr/UMR7139/en/structure.html ) which are used in the food industry as gelling agents in for example, ice-cream and puddings.
There are many other reasons which make them fascinating to study. As the brown algae, this group is yet quite unknown. It is therefore interesting to study these seaweeds’ development, functions and interactions with their environment.
Because of the importance of the studies done the red alga, Chondrus crispus, we chose to present to you this example:
Chondrus crispus
Chondrus crispus
photography taken from the web site of the Functional Genetic team, part of the Algal Genetic group in the Station Biologique de Roscoff at:
http://www.sb-roscoff.fr/UMR7139/en/geno-rech.html
Chondrus crispus is a red alga which is commonly called the “Irish moss” and can be found along the Atlantic coasts of Europe and the northern east coast of the United States, as well as in the Northern Pacific Ocean.
It is being studied more specifically as an interesting potential genetic model organism for the red macro algae. It is in fact easily cultivated in the laboratory, and proteins, RNAs, polysaccharides and other biomolecules are easily extracted.
Developing this model will enable to acquire a lot of genetic data and therefore more tools to understand more specific aspects of the red algae’s biology like:
• their response to stress and the stress signal transduction.
• The interactions of this alga with other organisms which includes defence towards pathogens and epiphytes.
• The identification of genes that code for the cell wall of the alga and more especially for the carraghenans which are important commercial polysaccharides found in red algae.
Like for Ectocarpus siliculosus, scientists would be very interested in having Chondrus crispus complete genome sequence (see genomics) in order to identify genes (see genetics) involved in different phenomena more easily. The demand for the sequencing of the genome has been made to the Genoscope in Evry in March 2006.
Scientists are, at the moment, trying to define the alga’s characteristics as precisely as possible to define the strain to be sequenced. They are making studies to make sure DNA, RNA and proteins can be extracted from the seaweed and to be sure they’re able to go through its life history.
Transcriptomics are being used to see what genes are expressed in different conditions of stress: high light, high temperature, osmotic choc and nitrogen limitation. Algae are exposed to one stress at the time in the laboratory. Then, thanks to cDNA microarrays, scientists can tell which specific genes are expressed in each case. This high-throughput technique has the advantage of being totally impartial; scientists have no idea of what they can get as a result. This is important as the organism is quite unknown, therefore, looking only at some specific gene’s expression would not be as conclusive. In this way new proteins important for stress responses can be identified.
Result of a microarray experiment
credit: Jonas Collen
This picture shows the result of a microarray experiment. The cDNAs representing the level of mRNAs in the normal condition are marked with green fluorescent probes and the mRNAs of the stressed organism are marked with red fluorescent probes. The dots which are a mix of the two colours represent genes that are expressed in both conditions. (for further explaination, go to microarrays)
Here the stressed organisms are protoplasts which means their cell wall have been removed completely, which is, of course a very stressful condition for the organisms.
Functional genomics can also be used to identify a transcript of a molecule that has previously been identified as important by a physiological approach like it has been done in the context of the study of red algae’s defence towards a pathogen, for example.
The Functional Genetic team which is a part of the Marine plants and biomolecules group in the Station Biologique de Roscoff is working on this alga. Jonas Collen and Catherine Boyen are organizing an international consortium of 38 laboratories and companies in 23 countries on Chondrus crispus to support and coordinate a possible sequencing of the genome like there is one already on Ectocarpus siliculosus.
Once the genomics and transcriptomics solid bases will be formed, scientists will be able to use the background knowledge to look into more specific research questions.
By going out on the inter-tidal zone and studying the seaweed when it is under natural environmental stress: for example, at low tide when there is a lot of sunshine, and comparing which genes are expressed at that time to the results obtained from the laboratory experiments, scientists will be able to tell which is the most stressful element in the seaweed’s environment. For example, it might be possible to say that high temperature is more stressful than desiccation.
Being able to say what is actually limiting the growth of seaweed in a specific situation is possible with the functional genomic approach. This could possibly be interesting in terms of applications as far as aquaculture, for example, to limit the input of fertilizers which also have ecological repercussions.
More fundamentally, the great amount of knowledge which is being generated by high throughput analysis will enable to go towards the understanding of why species grow in specific places but also towards the general understanding of these organism’s inner mechanisms.
copyright: http://www.ifremer.fr/aquaculture/fr/algues/macroalgues.htm
For further explanation, go to: http://www.sb-roscoff.fr/UMR7139/en/genomics.html
If you want to see more pictures and see how different this alga can look from place to place, go to: http://www.algaebase.org/speciesdetail.lasso?species_id=19519
More information about algae in general, go to:
www.seaweed.ie
