Washington DC (SPX) May 12, 2011
Scientists have discovered that marine diatoms, tiny phytoplankton abundant in the sea, have an animal-like urea cycle, and that this cycle enables the diatoms to efficiently use carbon and nitrogen from their environment.
The researchers, from the J. Craig Venter Institute (JCVI) and other institutions, published their findings in this week's issue of the journal Nature.
The team, led by lead author Andrew Allen from JCVI and co-author Chris Bowler, Institute of Biology, Ecole Normale Superieure, Paris, believes that the cycle could be a reason for the domination of diatoms in marine environments, especially after upwelling events--the upward movement of nutrient rich waters from the deep ocean to the surface.
In response to ocean upwelling, diatoms are able to quickly recover from prolonged periods of nutrient deprivation and rapidly proliferate.
"This study provides fascinating insights into how diatoms have evolved to become the dominant primary producers in many ocean regions," says David Garrison, program director in the National Science Foundation's (NSF) Division of Ocean Sciences, which funded the research along with NSF's Division of Molecular and Cellular Biosciences.
Diatoms have unique cell walls made of silica. They are key organisms for understanding the environmental health of marine ecosystems, and are responsible for much of the carbon and oxygen production in the ocean.
Diatom photosynthesis in ocean environments is also responsible for about one fifth of the oxygen in the atmosphere.
In previous research, Allen, Bowler and colleagues sequenced the genome of the first pennate diatom, Phaeodactylum tricornutum.
In that research, they developed new methods for determining the origin of diatom genes. They also looked at nutrient metabolism in diatoms, beginning with iron metabolism.
Building on that work, Allen and colleagues explored the evolutionary history of diatoms, specifically P. tricornutum, and cellular mechanisms for nutrient utilization in the environment, leading to the finding that diatoms have a functional urea cycle.
This was a stunning discovery, says Allen, because it was thought that the urea cycle originated with the metazoan (animal) branch of life.
There it has played an important role in facilitating a wide range of physiological innovations in vertebrates.
For example, urea synthesis enables rapid control of minerals and salts in the blood in animals such as sharks, skates, rays and bony fish, and ammonia detoxification associated with water retention in amphibians and mammals.
The latter was likely a prerequisite for life on land, and subsequently enabled the biochemical pathways necessary for processing a high-protein diet.
Allen and others have now shown that the urea cycle originated hundreds of millions of years before the appearance of metazoans.
The team used RNA interference techniques to partially silence a key urea cycle enzyme in diatoms.
Paper co-author Alisdair Fernie of the Max-Planck Institute of Molecular Plant Physiology evaluated the metabolite profile of diatoms with and without an impaired urea cycle.
Then Allen analyzed the data and found that urea cycle metabolites are critical for cellular recycling of carbon and nitrogen.
The metabolites are also important for facilitating the rapid onset of exponential growth characteristic of diatom recovery from nutrient starvation.
"It appears that the animal urea cycle, critical for cellular export of carbon and nitrogen wastes, was co-opted from an ancestral pathway that originally evolved as a nitrogen and carbon recycling and recovery mechanism," says Allen.
"This is a very interesting finding we didn't expect to see, and essentially changes the way we view diatoms relative to animals and plants."
The work also suggests that diatoms have followed a fundamentally different evolutionary path from plants--the dominant oxygen producers in terrestrial environments, green algae, and other closely related organisms.
Rather, prior to evolutionary acquisition of photosynthetic machinery, the ancestors of diatoms were possibly more closely related to the ancestors of animals than to plants.
This relatedness has resulted in diatoms and animals sharing some similar biochemical pathways such as the urea cycle.
Although it appears that animals and diatoms ultimately use the urea cycle for different purposes, they are evolutionarily linked in a way that animals and plants are not.
Along with Allen, Bowler, Fernie and other colleagues from JCVI, Ecole Normale Superieure, and Max-Planck Institute, Germany, researchers from the Biology Centre ASCR, the Institute of Parasitology and University of South Bohemia, Czech Republic; the University Federal de Vicosa, Brazil; and the Institute of Hydrobiology, Chinese Academy of Sciences, China, contributed to this work. The research was also funded by the JCVI, the European Commission on Diatomics Project, the Agence Nationale de la Recherche in France, and the Czech Science Foundation.
Share This Article With Planet Earth
Ecole Normale Superieure
Water News - Science, Technology and Politics
Darkness Stifles Reproduction of Surface-Dwelling Fish
Raleigh NC (SPX) May 12, 2011
Fish accustomed to living near the light of the water's surface become proverbial "fish out of water" when they move to dark environments like those found in caves, according to a study from North Carolina State University. In research published this week in Biology Letters, a Royal Society scientific journal, NC State post-doctoral researcher Rudiger Riesch and colleagues found that Atlan ... read more
New setbacks at Japan nuclear plant|
Nuclear stigma adds to Japan's pain
Japan decides on TEPCO compensation scheme: media
Spain scrambles tents, food for refugees of deadly quake
Lessening the Dangers of Radiation
Silver cycle: New evidence for natural synthesis of silver nanoparticles
NIST super-stable laser shines in minivan experiment
Russia says fire put out near radioactive facility
Darfur forum to seek $1.4 billion in water aid: UN
Climate Record Suggesting Severe Tropical Droughts as Northern Temperatures Rise
Israel exploiting Jordan Valley: rights group
Iran expert alarmed by 'critical' Caspian Sea pollution
States set rules on exploiting Arctic wealth
Antarctic icebergs help the ocean take up carbon dioxide
Change is the order of the day in the Arctic
Arctic countries seek cooperation as ice melts
Japan recalls tea over radiation fears
Drought tolerance in crops: Shutting down the plant's growth inhibition under mild stress
New Strategy Aims to Reduce Agricultural Ammonia
'Liquid smoke' from rice shows potential health benefits
Italian volcano eruption forces airport closure
Spanish seismologist had predicted a quake "shortly"
New cities near Istanbul to counter quake threat
5.1 quake kills eight, topples buildings in Spain
Burkina Faso ruling party says opposition aiming for coup
Chinese army gives rocket launchers, weapons to Sierra Leone
Disaster-hit Japan will not cut aid to Africa: spokesman
Diehard pro-Gbagbo militia begin to disarm
Indian brides told to put down their mobile phones
Super-healing researcher follows intuition
No nuts for 'Nutcracker Man'
Why the eye is better than a camera at capturing contrast and faint detail simultaneously
|The content herein, unless otherwise known to be public domain, are Copyright 1995-2010 - SpaceDaily. AFP and UPI Wire Stories are copyright Agence France-Presse and United Press International. ESA Portal Reports are copyright European Space Agency. All NASA sourced material is public domain. Additional copyrights may apply in whole or part to other bona fide parties. Advertising does not imply endorsement,agreement or approval of any opinions, statements or information provided by SpaceDaily on any Web page published or hosted by SpaceDaily. Privacy Statement|