Palo Alto, CA Although scientists have been able to sequence the genomes of many organisms, they still lack a context for associating the proteins encoded in genes with specific biological processes. To better understand the genetics underlying plant physiology and ecologyespecially in regard to photosynthesisa team of researchers including Carnegie's Arthur Grossman identified a list of proteins encoded in the genomes of plants and green algae, but not in the genomes of organisms that don't generate energy through photosynthesis. Their work will be published June 17 in the Journal of Biological Chemistry.
Using advanced computational tools to analyze the genomes of 28 different plants and photosynthetic organisms, Grossman and his colleagues at the University of California in Los Angeles and the Joint Genome Institute of the Department of Energy were able to identify 597 proteins encoded on plant and green algal genomes, but that are not present in non-photosynthetic organisms. They call this suite of proteins the GreenCut.
Interestingly, of the 597 GreenCut proteins, 286 have known functions, while the remaining 311 have not been associated with a specific biological process and are called "unknowns."
The majority of the GreenCut proteins, 52 percent, have been localized in a cellular organelle called the chloroplast--the compartment where photosynthesis takes place. It is widely accepted that chloroplasts originated from photosynthetic, single-celled bacteria called cyanobacteria, which were engulfed by a more complex, non-photosynthetic cell more than 1.5 billion years ago. While the relationship between the two organisms was originally symbiotic, over evolutionary time the cyanobacterium transferred most of its genetic information to the nucleus of the host organism, losing its ability to live independent of its partner.
"This genetically-reduced cyanobacterium, which is now termed a chloroplast, has maintained
|Contact: Arthur Grossman |