Genoma de alga marrom revela como a vida superior surgiu na Terra

domingo, junho 13, 2010

How Did Higher Life Evolve? Brown Algal Genome Opens New Door to Understanding Multicellularity and Photosynthesis

ScienceDaily (June 4, 2010) — With the world's first complete sequencing of a brown algal genome, an international research team has made a big leap towards understanding the evolution of two key prerequisites for higher life on Earth -- multicellularity and photosynthesis. As reported in the journalNature, about 100 scientists and technicians, during a five-year research project, successfully decoded all hereditary information -- commonly known as the "genome" -- on Ectocarpus siliculosus, an up to 20 cm large brown seaweed, which occurs mainly along coastlines in temperate latitudes. They have analyzed approximately 214 million base pairs and assigned these to about 16,000 genes. The biologists, Dr. Klaus Valentin and Dr. Bank Beszteri of the Alfred Wegener Institute for Polar and Marine Research in the Helmholtz Association have been involved in this global project since the planning phase in 2005.

Ectocarpus siliculosus (here growing on Zostera) occurs mainly along coastlines in temperate latitudes. (Credit: Photo by Akira Peters, Station Biologique Roscoff)

The sequencing of the brown algal genome is also a milestone in the efforts to reconstruct the evolution of photosynthesis. "We now know that oxygen-producing photosynthesis was „invented" before about 3.8 billion years ago, by cyanobacteria, sometimes erroneously called 'blue-green algae'," says Valentin about the elemental capability of plants to convert sunlight into biologically usable energy, whilst releasing oxygen. "Green and red algae have developed this ability after their ancestors scavenged living cyanobacteria, and thus more or less captured photosynthesis, to the benefit of both sides, since this symbiosis resulted in tremendous competitive advantages in the primordial ocean."

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The Ectocarpus genome and the independent evolution of multicellularity in brown algae

J. Mark Cock, Lieven Sterck, Pierre Rouzé, Delphine Scornet, Andrew E. Allen, Grigoris Amoutzias, Veronique Anthouard, François Artiguenave, Jean-Marc Aury, Jonathan H. Badger, Bank Beszteri, Kenny Billiau, Eric Bonnet, John H. Bothwell, Chris Bowler, Catherine Boyen, Colin Brownlee, Carl J. Carrano, Bénédicte Charrier, Ga Youn Cho, Susana M. Coelho, Jonas Collén, Erwan Corre, Corinne Da Silva,
Ludovic Delage et al.



Corresponding author

Nature 465, 617–621 (03 June 2010) doi:10.1038/nature09016Received 09 November 2009 Accepted 15 March 2010

Brown algae (Phaeophyceae) are complex photosynthetic organisms with a very different evolutionary history to green plants, to which they are only distantly related1. These seaweeds are the dominant species in rocky coastal ecosystems and they exhibit many interesting adaptations to these, often harsh, environments. Brown algae are also one of only a small number of eukaryotic lineages that have evolved complex multicellularity (Fig. 1). We report the 214 million base pair (Mbp) genome sequence of the filamentous seaweed Ectocarpus siliculosus (Dillwyn) Lyngbye, a model organism for brown algae2, 3, 4,5, closely related to the kelps6, 7 (Fig. 1). Genome features such as the presence of an extended set of light-harvesting and pigment biosynthesis genes and new metabolic processes such as halide metabolism help explain the ability of this organism to cope with the highly variable tidal environment. The evolution of multicellularity in this lineage is correlated with the presence of a rich array of signal transduction genes. Of particular interest is the presence of a family of receptor kinases, as the independent evolution of related molecules has been linked with the emergence of multicellularity in both the animal and green plant lineages. The Ectocarpusgenome sequence represents an important step towards developing this organism as a model species, providing the possibility to combine genomic and genetic2 approaches to explore these and other4, 5 aspects of brown algal biology further.

Subject terms: Evolution  Developmental biology