An international team of biologists led by Indiana University's David M. Kehoe has identified both the enzyme and molecular mechanism critical for controlling a chameleon-like process that allows one of the world's most abundant ocean phytoplankton, once known as blue-green algae, to maximize light harvesting for photosynthesis.
Responsible for contributing about 20 percent of the total oxygen production on the planet, the cyanobacteria Synechococcus uses its own unique form of a sophisticated response called chromatic acclimation to fine tune the absorption properties of its photosynthetic antenna complexes to the predominant ambient light color. The researchers identified and characterized an enzyme, MpeZ, that plays a pivotal role in the mechanism that allows two different water-soluble proteins in Synechococcus -- phycoerythrin I and II -- to alter their pigmentation in order to maximize photon capture for photosynthesis.
Scientists want to understand how cyanobacteria optimize their photosynthetic activities in different light conditions to gain a better appreciation of how human activities affect the phytoplankton's ability to produce oxygen and uptake the greenhouse gas carbon dioxide, which they consume in order to grow. Science and industry also use the pigment-protein complex phycoerythrin for fluorescent imaging and as fluorescent markers in biotechnology and health care applications.
"We now have the ability to attach a novel chromophore, part of a molecule responsible for its color, to phycoerythrin, which provides a new chromophore-protein combination that absorbs and fluoresces at a wavelength that is not currently commercially available," said Kehoe, a professor in the IU Bloomington College of Arts and Sciences' Department of Biology. "Our results suggest that this new chromoprotein is brighter and more stable than most on the market today."
Kehoe also noted IU has begun the process of filing a patent on the invention.
The team found that the gene encoding the MpeZ enzyme is activated in blue light. Once produced, MpeZ then binds to antenna proteins containing pigments that normally catch green light and attaches an alternative chromophore that allows the antennae to capture blue light. The specific mechanism, called type IV chromatic acclimation, involves replacing three molecules of the green light-absorbing chromophore with an equal number of blue light-absorbing chromophore. This color-shifting is reversible and is controlled by the ratio of blue to green light in the environment.
"These 'chromatic adapters' are true chameleons that can efficiently live in green coastal waters as well as in blue offshore waters by modifying their pigmentation," Kehoe said. "Synechococcus cells maintained in blue light harvest preferentially blue light, while cells grown in green light harvest more green."
"A phycoerythrin-specific bilin lyase-isomerase controls blue-green chromatic acclimation in marine Synechococcus" was published online in the Early Edition of Proceedings of the National Academy of Sciences. Co-authors with Kehoe, also affiliated with IU Bloomington's Indiana Molecular Biology Institute, were IU Ph.D. student Animesh Shukla; Avijit Biswas and Wendy M. Schluchter of the University of New Orleans; Nicolas Blot of Université Pierre et Marie Curie - Paris 06, the Centre National de la Recherche Scientifique and Clermont Université in France; Frederic Partensky and Laurence Garczarek of Université Pierre et Marie Curie - Paris 06 and the Centre National de la Recherche Scientifique; IU Bloomington Department of Chemistry METACyt Biochemical Analysis Center mass spectrometry facility manager and assistant scientist Jonathan A. Karty and assistant scientist Loubna A. Hammad; and former IU biology graduate student Andrian Gutu, now of Harvard University.
Indiana University: http://newsinfo.iu.edu
This press release was posted to serve as a topic for discussion. Please comment below. We try our best to only post press releases that are associated with peer reviewed scientific literature. Critical discussions of the research are appreciated. If you need help finding a link to the original article, please contact us on twitter or via e-mail.
A major international study finds that killings among chimpanzees result from normal competition, not human interference.
Clownfish travel hundreds of kilometres, but it is the larvae rather than the adults that migrate
U.S. government researchers working with divers and sonar equipment have located the wrecks of what they dubbed "forgotten ghost ships" in waters just outside San Francisco's Golden Gate strait.
"It's spooky," a Clearwater, Fla., fisherman said, comparing the toxic algae bloom to "boiled red Georgia clay"
Physicist Danielle Bassett has been awarded a MacArthur Fellowship based on her work studying the human brain. She talks with Melissa Block about the advances it may lead to.
A team of researchers are using multispectral imaging to uncover hidden text on a 1491 Martellus map, one of the most important maps in history. Lead researcher Chet Van Duzer thinks the discoveries will allow historians and scholars to see just how the map influenced cartography in its time.
Genetic evidence from ancient humans and modern people suggests that travelers from northern Eurasia moved south several thousand years ago. They stuck around to have kids with early European farmers.
Kissing bugs, which can spread Chagas disease, turned up positive for human blood meals in caves in Guatemala and Belize
Epilepsy can be very disruptive and debilitating, but can it also spur creativity? If treatments suppress comedic inspiration and this directly affects your job, is it worth it?
Rising temperatures and a more acidic ocean may spell trouble for the Chesapeake Bay's iconic crabs, oysters and fish