'LA VIE EN ROUGE' OR, THE GENOME OF THE RED SEAWEED IRISH MOSS (Chondrus crispus)
An international consortium of scientist including researchers at the Centre for Genomic Regulation (CRG) in Barcelona has sequenced the genome of the common red seaweed, Irish moss (Chondrus crispus). With this work we now know much more about how red algae work, how they make their biomolecules, and the evolution of plants and algae. The results have been published this week in Proceedings of the National Academy of Sciences.

Walking on a rocky intertidal shore you will see a fascinating landscape often dominated by large algae of different sorts. It is a beautiful environment full of fantastic discoveries including the enigmatic seaweeds. Despite the absence of flowers, colour is not lacking among the algae; the normal colour of grass and herbs is here often replaced with more red and brown than green. The red colour is provided by the red seaweeds.

The red seaweeds are the evolutionary sister group to all green plants and algae and had common ancestor approximately 1,500 million years ago. Compared to the green plants we know very little of red algae, even though according to the secondary endosymbiosis theory, their photosynthetic machinery has been adopted by a majority of the phytoplankton, including diatoms and dinoflagellates.

To learn more about these enigmatic plants an international consortium has analyzed the genome of Chondrus crispus, or Irish moss. The consortium is led by the Station Biologique de Roscoff in Brittany, France, belonging to Le Centre national de la recherche scientifique (CNRS) and Université Pierre et Marie Curie (UPMC). The genome was sequenced and informatically annotated by the French National Sequencing Center, Genoscope. In Spain, the Centre for Genomic Regulation (CRG) has contributed with the comparative analysis of this new sequenced genome by comparing it with other genomes of plants and algae already sequenced.

Chondrus is an up to 20 cm typical red seaweed commonly found on rocky shores in the Northern Atlantic but also in all the European Atlantic shore and in the South of Spain. This species has historically been used as one way to make blancmange, a dessert that can be made by boiling Irish moss with milk and sugar. The compound that thickens the milk, carrageenan, is nowadays used in the food industry (E407) in products like ice-cream and pudding. Globally, red algae are used as food and as a source of thickeners and represent a value of over 2,000 million US dollars annually.

“What we found when analysing the genome was that the red seaweeds are very different to their green cousins: they have fewer genes than most of their green relatives, the genes are more compact and many genes are not found in the two groups”, explains Jonas Collén, principal investigator of the project. The sequencing of the genome has helped us to understand the evolution of plants. “One of the important questions we had in this project was to identify which genes of the red algae can be also found in other species. There are lineages that established symbiotic relationships with protozoa and it was thought that this relationship allowed them to get new genes”, adds Toni Gabaldón, group leader of the Comparative Genomics lab at the CRG.

The results of this research propose that the red algae went through a bottleneck in their evolution, loosing many of the genes and reducing their size. Today’s land plants and trees are green; without this bottleneck for the red algae maybe our trees and flowers would have been red...

The genome also helps us to understand how the red algae are related to other organisms, how they live in their environment and how they produce their biomolecules, such as carrageenans, and will greatly accelerate efforts to understand the biology of these fascinating organisms in the coming years.

The Chondrus consortium included laboratories from France, Germany, United Kingdom, Czech Republic, Spain, Egypt, Norway and Greece. The French Genome Center Genoscope provided major funding, informatics support and sequencing strategy.

Reference:
Genome structure and metabolic features in the red seaweed Chondrus crispus shed light on evolution of the Archaeplastida. Jonas Collén, Betina Porcel, Wilfrid Carré, Steven G. Ball, Cristian Chaparro, Thierry Tonon, Tristan Barbeyron, Gurvan Michel, Benjamin Noel, Klaus Valentin, Marek Elias, François Artiguenave, Alok Arun, Jean-Marc Aury, José F. Barbosa-Neto, John H. Bothwell, François-Yves Bouget, Loraine Brillet, Francisco Cabello-Hurtado, Salvador Capella-Gutiérrez, Bénédicte Charrier, Lionel Cladière, J. Mark Cock, Susana M. Coelho, Christophe Colleoni, Mirjam Czjzek, Corinne Da Silva, Ludovic Delage, France Denoeud, Philippe Deschamps, Simon M. Dittami, Toni Gabaldón, Claire M. M. Gachon, Agnès Groisillier, Cécile Hervé, Kamel Jabbari, Michael Katinka, Bernard Kloareg, Nathalie Kowalczyk, Karine Labadie, Catherine Leblanc, Pascal J. Lopez, Deirdre H. McLachlan, Laurence Meslet-Cladiere, Ahmed Moustafa, Zofia Nehr, Pi Nyvall Collén, Olivier Panaud, Frédéric Partensky, Julie Poulain, Stefan A. Rensing, Sylvie Rousvoal, Gaelle Samson, Aikaterini Symeonidi, Jean Weissenbach, Antonios Zambounis, Patrick Wincker and Catherine Boyen, Proceedings of the Natural Academy of Sciences (PNAS). Online published week of March 11, 2013.

Contact:
Laia Cendrós - Press Office – Centre for Genomic Regulation (CRG)