Green Alga Genome Project Catalogs Carbon Capture Machinery; Opportunities for Improving Efficiencies of Biofuels Production
The genome analysis of the single-celled alga Chlamydomonas reinhardtii has uncovered hundreds of genes that are uniquely associated with carbon dioxide capture and generation of biomass. Among the 15,000-plus genes revealed in the study are those that encode the structure and function of the specialized organelle that houses the photosynthetic apparatus, the chloroplast, which is responsible for converting light to chemical energy.
The project, led by the US Department of Energy Joint Genome Institute (DOE JGI); the University of California, Los Angeles; and the Carnegie Institution, and including contributions from more than 100 international collaborators, is featured in the 12 October edition of the journal Science.
The Chlamy genome is like a green time capsule that affords a view into the complex core machinery that gave rise to today’s energy-capturing and oxygen-producing chloroplasts. DOE JGI’s particular interest in Chlamy centers on its keen ability to efficiently capture and convert sunlight into energy, and its role in managing the global pool of carbon— Daniel Rokhsar, DOE JGI Computational Biology Program head and project co-leader
The sequence analysis presents a comprehensive set of genes required for these capabilities. Rokhsar said that with these data now publicly available, new strategies for biology-based solar energy capture, carbon assimilation, and detoxification of soils by employing algae to remove heavy metal contaminants will begin to surface. The analysis will also shed light on the capabilities of related algae that can produce biodiesel and biocrude as alternatives to fossil fuels.
The results will also help researchers figure out the construction of chloroplasts, which house the machinery inside plant and algal cells that serves as “solar panels,” absorbing sunlight and coupling carbon dioxide and water to produce the starting materials, sugars, that fuel all other metabolic processes. These pathways, described in the DNA sequence, represent opportunities for improving efficiencies for this conversion process and ultimately biofuels production.
The published analysis of approximately 120 million units of DNA sequence generated by DOE JGI showed that Chlamy shares nearly 7,000 genes with other organisms; more than a third of these are shared by both humans and flowering plants, which helps support the argument for their common ancestry. Many of these genes are normally associated with animals, such as those that describe the circuitry for flagella, enabling this alga to swim. Others have affinity with the earth’s early photosynthetic organisms, cyanobacteria, dating far back into Precambrian times, more than three billion years ago, when biodiversity began its explosive proliferation.
Although Chlamydomonas is a plant, there are clear similarities between this photosynthetic organism and animals that would surprise the average person on the street. Just 20 years ago, no one would have guessed that an alga would have retained many of the functions we associate with humans and would be useful for developing a basic understanding of certain human diseases.—Arthur Grossman, Carnegie Institution, project co-leader
This resource may inform possible therapeutic strategies for human diseases associated with the fine hair structures of the cilia and flagella—for instance, the neurological movement disorder dyskinesia; polycystic kidney disease (PKD); and some forms of liver, respiratory and retinal degeneration disease.
Co-leaders on the project in addition to Rokshar and Grossman were DOE JGI Computational Scientist Simon Prochnik and Sabeeha Merchant of UCLA.
Other DOE JGI authors on the Chlamy Science paper include Astrid Terry, Asaf Salamov, Erika Lindquist, Harris Shapiro, Susan Lucas; Jane Grimwood and Jeremy Schmutz at the Stanford Human Genome Center; and the Chlamydomonas Annotation Team led by Igor Grigoriev and including Peter Brokstein, Inna Dubchak, David Goodstein, Leila Hornick, Wayne Huang, Jinal Jhaveri, Yigong Lou, Diego Martinez, Abby Ngau, Bobby Otillar, Alexander Poliakov, Aaron Porter, Lukasz Szajkowski, Gregory Werner, and Kemin Zhou.
Sabeeha S. Merchant, et. al. “The Chlamydomonas Genome Reveals the Evolution of Key Animal and Plant Functions” Science 12 October 2007: Vol. 318. no. 5848, pp. 245 - 250 DOI:10.1126/science.1143609