Brainy genes, not brawn, key to success on mussel beachOctober 10, 2008It's hard being a mussel: you have to worry about hungry starfish and even hungrier humans, not to mention an environment that can change your body temperature 50 degrees Fahrenheit in just a few hours. "It's one of the most variable habitats on Earth," said USC biologist Andrew Gracey. "Mussels can spend part of the day bathed in cool Pacific seawater and the other part baked under the California sun." Gracey led the first real-time molecular sampling of mussels in their natural habitat, the results of which appear online Oct. 9 in the journal Current Biology. The researchers found that the hardy mollusks alternate between expressing genes associated with eating and genes associated with growing. Scientists have thought that mussels survive their harsh home on the rocks by just being tough, but this study suggests a more sophisticated strategy. "They spend part of the day respiring, and doing metabolic processes, and then the other part of the day switching to cell division," Gracey explained. Because their environment is so unpredictable-at low tide mussels could scorch on a sunny day and get soaked on a stormy one-these regular cycles were unexpected. "To be honest, I first thought they'd be wasting their time to be constantly switching on this gene and switching off that gene," Gracey said. The scientists also found that as the environment became harsher-like higher up the rocks-the oscillations in gene expression became more pronounced. Mussels use genes to weather the heat In addition to cyclic expression, the study found that mussels use two sets of genes to respond to heat stress-sometimes reacting to temperature changes in seconds. "Day-in, day-out, they switch on a particular set of genes associated with routine heat stress, but when the day got very hot we saw this other battery of genes dealing with really extreme temperatures," Gracey said. The first set of genes triggers the formation of chaperones that prevent proteins from unraveling, while the second set creates proteins that shepherd damaged material away. This could have implications for climate change and how a key species like mussels-fundamental to the ecology of inter-tidal rocky zones-would adapt to a hotter world. In addition, there are implications for understanding sudden summer mortality syndrome, a mysterious die-off that can devastate oyster farms, and which is believed to be linked to a stress event like heat. Gene oscillation as survival strategy Expressing genes in waves appears to be a survival strategy, one that has been seen in lab experiments involving yeast. "There are certain physiological processes that are fairly incompatible, like respiration and cell division," Gracey explained. Respiration creates free radicals, and if an organism undergoes cell division at the same time, those free radicals could damage DNA. (This is partly why antioxidants in green tea and pomegranates are popular these days, since they remove free radicals.) By keeping respiration and cell division separate, mussels can decrease the chances of such cell damage-an advantage in such extreme conditions. What controls the cycles? In humans, the circadian rhythm is also a cycle that involves waves of gene expression, but unlike the mussel cycles, it has consistent intervals regulated by light. "Periods are typically constant, and typically they're following something related to a 24-hour cycle," Gracey noted. "Our data doesn't conform to that." It's not yet clear what is driving the cycles in mussels. It could be temperature, how much time is spent out of the water, or the opportunity to feed-but it's hard to pin down a single variable. (A new grant from the National Science Foundation will help Gracey and colleagues tackle that question through lab simulations.) Study methods The scientists collected genetic material every three to four hours over three days, sampling mussel beds just south of the Monterey Bay Aquarium in California. They also installed "robo-mussels"-chips sealed in silicon-to record body temperature. Back in the lab, the DNA was sequenced and bound to 10,000 points on a "gene chip," or DNA microarray. They then extracted RNA-the messenger that commands expression of a certain gene-from the samples at the 20 successive time points. RNA from two consecutive points was then converted to DNA, which was labeled with two different dyes. These two types of DNA were then allowed to bind with different points on the microarray, which correspond to different points on the mussel genome. Thanks to the dyes, the scientists could then observe which sample from which time point bound relatively more to a specific part of the mussel genome. When this was determined, the functions of those genes that were expressed more at that point in time could be inferred based on their similarity to genes in public databases. University of Southern California |
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| Related Mussel Current Events and Mussel News Articles New American Chemical Society podcast: Tiny sea creature and a new medical adhesive Scientists questing after a long-sought new medical adhesive describe copying the natural glue secreted by a tiny sea creature called the sandcastle worm in the latest episode in the American Chemical Society's (ACS) award-winning podcast series, "Global Challenges/Chemistry Solutions." NOAA Announces an Experimental Harmful Algal Bloom Forecast Bulletin for Lake Erie Predicting harmful algal blooms, or HABs, in the Great Lakes is now a reality as NOAA announces an experimental HAB forecast system in Lake Erie. The invasive green mussel may inspire new forms of wet adhesion The green mussel is known for being a notoriously invasive fouling species, but scientists have just discovered that it also has a very powerful form of adhesion in its foot, according to a recent article in the Journal of Biological Chemistry. Round Goby invade Great Lakes Canadian scientists uncover alarming invasion of round goby into Great Lakes tributaries: impact on endangered fishes likely to be serious. Zebra mussels hang on while quagga mussels take over The zebra mussels that have wreaked ecological havoc on the Great Lakes are harder to find these days - not because they are dying off, but because they are being replaced by a cousin, the quagga mussel. But zebra mussels still dominate in fast-moving streams and rivers. NOAA Report Calls Flame Retardants Concern to U.S. Coastal Ecosystems NOAA scientists, in a first-of-its-kind report issued today, state that Polybrominated Diphenyl Ethers (PBDEs), chemicals commonly used in commercial goods as flame retardants since the 1970s, are found in all United States coastal waters and the Great Lakes, with elevated levels near urban and industrial centers. Cause of mussel poisoning identified The origin of the neurotoxin azaspiracid has finally been identified after a search for more than a decade. The Prestige oil spill caused changes in the cell structure of mussels The oil spill from the Prestige petroleum oil tanker in 2002 caused serious damage to the ecosystems in the Bay of Biscay. A PhD thesis at the University of the Basque Country (UPV/EHU) has studied the consequences of this spill for the mussels inhabiting this northern coast of the Iberian peninsula. Biological invasions increasing due to freshwater impoundments, says CU-Boulder study The growing number of dams and other impoundments is increasing the number of invasive species and the speed at which they spread, putting natural lakes at risk, says a study led by the University of Colorado at Boulder. New Ballast Treatment Could Help Shield Lake Superior from Deadly Fish Disease A Michigan Technological University professor has developed a new water treatment that could help keep a deadly fish disease out of Lake Superior. More Mussel Current Events and Mussel News Articles |
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