Controlling algal blooms

February 20, 2006

Diatoms, highly successful photosynthetic plankton responsible for 40% of the net primary production in the oceans, undergo seasonal population explosions called phytoplankton blooms that attract billions of krill, copepods, and other grazing predators. As a defense, wounded diatoms release aldehyde compounds that minimize future diatom casualties by compromising the hatching success of grazers. But these diatom-derived aldehydes can also kill diatoms.

In a new study, Assaf Vardi, Chris Bowler, and their colleagues investigated the possibility that the contrasting effects of aldehydes reflect their role as "infochemicals" that trigger different responses attuned to changing conditions in the diatoms' habitat. The authors found that different concentrations of the aldehyde decadienal produce different diatom responses. At low doses, aldehydes induce resistance to the compound's toxic effects. High aldehyde concentrations, on the other hand, trigger cell death, which may lead to termination of a bloom. Thus, diatom-derived aldehydes regulate the population dynamics of both diatoms and their predators.

Treated cells succumbed to decadienal in a time- and dose-dependent manner, with significant increases in fatalities above a specific threshold. Below this threshold, cells survived, but underwent cell cycle arrest. Monitoring nitric oxide levels with a nitric oxide-sensitive fluorescent dye and time-lapse imaging revealed that both diatom species experienced similar bursts of nitric oxide production about five minutes after decadienal treatment. To clarify nitric oxide's role in cell death, the authors stimulated nitric oxide production without using decadienal by using molecules called nitric oxide donors and found that the number of dying cells increased along with the levels of nitric oxide.

Interestingly, nitric oxide production levels varied among the diatoms. Some cells showed rapid increases in nitric oxide production while their neighbors showed delayed responses, suggesting that the signal to produce nitric oxide was propagating through the diatom population. Healthy cells sensed the level of stressed cells in their midst by detecting the wounded cells' aldehyde-generated signal. Cells pretreated with a lower dose of decadienal before receiving a higher dose had far better survival and growth rates than cells treated with only a single high dose. These results suggest that lower decadienal doses may immunize cells, stimulating resistance to normally lethal aldehyde concentrations. This induced resistance may provide diatoms who escape grazing predators with a better chance of surviving the toxic aldehydes released by the dying diatoms.

Altogether, these results suggest that decadienal-like aldehydes not only affect the reproductive capacity of grazers but also act as infochemicals that monitor stress levels in diatom populations. During phytoplankton blooms, this stress surveillance system can induce resistance or death. The authors propose that this differential response, regulated by the sophisticated use of intracellular calcium and nitric oxide signals, may determine the fitness and succession of phytoplankton communities.
-end-
Citation: Vardi A, Formiggini F, Casotti R, de Martino A, Ribalet F, et al. (2006) A stress surveillance system based on calcium and nitric oxide in marine diatoms. PLoS Biol 4(3): e60.

CONTACT:
Chris Bowler
CNRS FRE2910/Ecole Normale Superiore
46 rue d'Ulm
Paris, France 75230 Cedex 05
+33-1-44-32-35-25
cbowler@biologie.ens.fr

Please mention the open-access journal PLoS BIOLOGY (www.plosbiology.org) as the source for these articles and provide a link to the freely-available text.

All works published in PLoS Biology are open access. Everything is immediately available--to read, download, redistribute, include in databases, and otherwise use--without cost to anyone, anywhere, subject only to the condition that the original authorship and source are properly attributed. Copyright is retained by the authors. The Public Library of Science uses the Creative Commons Attribution License.

PLOS

Related Cell Death Articles from Brightsurf:

Cell death in porpoises caused by environmental pollutants
Environmental pollutants threaten the health of marine mammals. This study established a novel cell-based assay using the fibroblasts of a finless porpoise stranded along the coast of the Seto Inland Sea, Japan, to better understand the cytotoxicity and the impacts of environmental pollutants on the porpoise population.

Gold nanoparticles to save neurons from cell death
An international research team coordinated by Istituto Italiano di Tecnologia in Lecce (Italy) has developed gold nanoparticles able to reduce the cell death of neurons exposed to overexcitement.

New light shone on inflammatory cell death regulator
Australian researchers have made significant advances in understanding the inflammatory cell death regulatory protein MLKL and its role in disease.

Silicones may lead to cell death
Silicone molecules from breast implants can initiate processes in human cells that lead to cell death.

New players in the programmed cell death mechanism
Skoltech researchers have identified a set of proteins that are important in the process of apoptosis, or programmed cell death.

Tumors hijack the cell death pathway to live
Cancer cells avoid an immune system attack after radiation by commandeering a cell signaling pathway that helps dying cells avoid triggering an immune response, a new study led by UTSW scientists suggests.

How trans fats assist cell death
Tohoku University researchers in Japan have uncovered a molecular link between some trans fats and a variety of disorders, including cardiovascular and neurodegenerative diseases.

Bacteria can 'outsmart' programmed cell death
To be able to multiply, bacteria that cause diarrhoea block mediators of programmed cell death, a new study in 'Nature Microbiology' shows.

Cell death or cancer growth: A question of cohesion
Activation of CD95, a receptor found on all cancer cells, triggers programmed cell death -- or does the opposite, namely stimulates cancer cell growth.

Cell death blocker prevents healthy cells from dying
Researchers have discovered a proof-of-concept drug that can prevent healthy cells from dying in the laboratory.

Read More: Cell Death News and Cell Death Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.