MUTATIONS RESPONSIBLE FOR ENVIRONMENTAL ADAPTATIONS
While my blog is rooted on Lake Malawi cichlids biodiversity, sometimes I find stories which are indirectly related to the issue of rapid radiation of Lake Malawi cichlids. As we may all know the puzzle in cichlid evolution is to solve the oring of this stunning biodiversity of Lake Malawi. Among the factors responsible for this puzzle are mate choice basing on the male breeding colour morphs. Today, the study in bacteria has managed to locate the mutations which are responsible for phenotypic changes due to environment. In simplistic sense, think of colour morphs in cichlids and water levels or environment or geographic locations in Lake Malawi, is it possible to indetify the mutations responsible?? Think of red tops (P. zebra), blue tops (P. zebra), blue black tops (P. zebra) and C. afra. Is it possible to locate the mutations responsible??
Now read on the story below:
==============================
Researchers for the first time have tracked the specific genetic mutations -- occurring over just a few generations -- that allow bacteria to respond to environmental changes, they report online in Nature today (November 4).
"We showed how evolution happens in real time," said Hubertus Beaumont, a biologist from Leiden University in the Netherlands and first author on the study.
Studies have shown bacteria and other organisms can switch back and forth between phenotypes to better survive in new environments. For instance, Beaumont said, many bacteria switch their surface antigens when invading a host, so they can avoid being attacked, and certain desert plants are programmed to germinate seeds at random time intervals, increasing their chances of encountering rain. "This bet-hedging strategy is very simple, but captures the essence of evolution." Beaumont said. "Natural selection in these uncertain environments causes an organism to evolve protective traits." Exactly how such phenotypic adaptability emerges, however, was unknown.
In order to observe how bet-hedging evolves, Beaumont and his colleague Paul Rainey at Massey University in New Zealand observed Pseudomonas fluorescens, a common rod-shaped bacterium, in a new type of environment. They already knew that the bacteria grow well in a test tube that's shaken manually or in an incubator that allows oxygen to circulate in the culture. So instead of shaking the test tube, a condition to which the bacteria are well-adapted, the researchers watched the bacteria grow in non-shaken test tubes.
As expected, some of the bacteria adapted to the novel environment, forming colonies with an advantageous "wrinkly" morphology as opposed to the ancestral bacteria, which grew smoothly. The team identified these new colony types in the test tube and transferred them to fresh tubes, repeating this process 15 times to select for the new variations. Eventually, the bacteria evolved the ability to rapidly switch their phenotypes between the "wrinkly" and "smooth" cell-types to prepare themselves to cope with the different environments.
"I find these results really intriguing," said Martin Ackermann, an environmental microbiologist at Eidgenössische Technische Hochschule Zurich (or ETH Zurich) in Switzerland who was not involved in the research. "It is amazing to see that phenotypic switching can evolve so rapidly, in the course of a just a few rounds of selection. As far as I know, this has not been observed before."
Beaumont and Rainey then sequenced the evolved bacterial genome and found all the mutations that had arisen and that might have contributed to this new trait. The team identified nine mutations distinguishing bet-hedgers from their ancestors. They pinpointed one specific mutation as the one which allows the phenotype to switch back and forth between different morphologies, while the other mutations, they found, were essential for growing the new type of bacteria.
"It's yet another beautiful study at multiple levels from Paul Rainey's team," said Richard Lenski, a microbial ecologist at Michigan State University who didn't participate in the research, in an email. "This is a neat demonstration that the evolution of bet-hedging was contingent on other mutations that had occurred earlier in the lineage." These earlier changes improved the fitness of the bacteria at each stage.
"The results thus suggest that phenotypic switching is a strategy that can readily evolve," and may capture the earliest evolutionary solutions to life in fluctuating environments, Ackerman wrote in an email.
Wednesday, November 4, 2009
Friday, October 23, 2009
Malawi at the root of humankind 6 MYA
Malawi could be the cradle of humankind-researcher
KARONGA, Malawi (Reuters) - The latest discovery of pre-historic tools and remains of hominids in Malawi's remote northern district of Karonga provides further proof that the area could be the cradle of humankind, a leading German researcher said.
Professor Friedemann Schrenk of the Goethe University in Frankfurt told Reuters that two students working on the excavation site last month had discovered prehistoric tools and a tooth of an hominid.
"This latest discovery of prehistoric tools and remains of hominids provides additional proof to the theory that the Great Rift Valley of Africa and perhaps the excavation site near Karonga can be considered the cradle of humankind," Schrenk said.
A hominid is a member of a family of primates which includes humans and their prehistoric ancestors.
The discovery was at Malema excavation site, 10 km (6 miles) from Karonga.
The site also contains some of the earliest dinosaurs which lived between 100 million and 140 million years ago and early hominids believed to have lived between a million and 6 million years ago.
He is leading a team of researchers from Europe and Africa to establish an African center for interdisciplinary studies on mammal and hominid evolution in the southern African nation.
Karonga is about 615 km (380 miles) north of the capital Lilongwe and is near the border with Tanzania.
KARONGA, Malawi (Reuters) - The latest discovery of pre-historic tools and remains of hominids in Malawi's remote northern district of Karonga provides further proof that the area could be the cradle of humankind, a leading German researcher said.
Professor Friedemann Schrenk of the Goethe University in Frankfurt told Reuters that two students working on the excavation site last month had discovered prehistoric tools and a tooth of an hominid.
"This latest discovery of prehistoric tools and remains of hominids provides additional proof to the theory that the Great Rift Valley of Africa and perhaps the excavation site near Karonga can be considered the cradle of humankind," Schrenk said.
A hominid is a member of a family of primates which includes humans and their prehistoric ancestors.
The discovery was at Malema excavation site, 10 km (6 miles) from Karonga.
The site also contains some of the earliest dinosaurs which lived between 100 million and 140 million years ago and early hominids believed to have lived between a million and 6 million years ago.
He is leading a team of researchers from Europe and Africa to establish an African center for interdisciplinary studies on mammal and hominid evolution in the southern African nation.
Karonga is about 615 km (380 miles) north of the capital Lilongwe and is near the border with Tanzania.
Wednesday, October 14, 2009
Pheromones may not initiate sexual attraction and mating
This story was taken from science magazine on as is basis, but found it interesting as I am working on mate choice of Lake Malawi cichlids as well. The role of chemical cues in cichlid mate choice has already being suggested but their relationship with the pheromeones (hydrocarbones) is yet to be told. The following study in drosophila has worked on such untouched components.
======= =========== ======== ========== ====== ========
Pheromones may not initiate sexual attraction and mating, as commonly believed, new research suggests. Instead, the chemical signals may help flies distinguish between different genders and species while choosing a mate, researchers report in this week's issue of Nature.
This is the first time a study has deciphered the chemical dialogue happening between flies as they mate," said Nicolas Gompel, a geneticist at the Institut de Biologie du Developpement de Marseille-Luminy in France, who was not involved with the research but wrote an accompanying commentary on the paper. "The research challenges the common belief that pheromones are essential to initiate courtship... and suggests that instead, [they] play a significant role in mate identification and selection."
Scientists have long understood that pheromones, hydrocarbons produced by an animal or insect that trigger reactions in another individual, play a role in mating. But they've been unable to identify the role of individual pheromones because the hydrocarbons are often secreted as blends, comprised of up to 30 molecules, and function in conjunction with other signals. In order to study individual pheromones, Jean-Christophe Billeter from the University of Toronto at Mississauga and his colleagues genetically engineered adult Drosophila melanogaster without oenocytes, cells that secret hydrocarbons. The oenocyte-less flies were "blank slates," said Joel Levine, a geneticist from the University of Toronto and coauthor of the study, allowing the team to imprint one pheromone at a time.
Because pheromones have been generally believed to stimulate mating, Billeter and his colleagues expected that flies lacking hydrocarbons would be sexually unappealing to males. To their surprise, quite the opposite happened: wild-type males were hyperattracted to oenocyte-less flies. The wild-type males also ignored gender, choosing to mate with both unscented males and females over other wild-types. These results led the researchers to conclude that pheromones may not stimulate mating, but may instead act to slow down male mating attempts to allow the female to assess her partner's suitability. They also concluded that hydrocarbons help flies distinguish between sexes.
Billeter and his colleagues then tested the effect of individual pheromones on mate selection and copulation attempts. Researchers treated unscented D. melanogaster with wild-type levels of cVA, a hydrocarbon males are known to coat on females to deter further mating attempts. As expected, cVA effectively created a "chemical chastity belt," said Gompel.
Researchers then treated unscented flies with 7,11-heptacosadiene (7,11-HD), a pheromone thought to act as an aphrodisiac for flies. Although 7,11-HD alone did not stimulate additional mating attempts, when applied over cVA, it helped diminish the inhibiting effect of the compound, allowing females to broadcast their mating availability. The findings suggested that mating doesn't depend on just one pheromone relaying a message of availability, but instead on a complex mixture of attractive and aversive signals.
7,11-HD also seemed to act as a species barrier in mating. Unscented D. melanogaster females treated with the hydrocarbon attracted males of the same species, but deterred D. simulans and D. yakuba males.
"It's neat that one hydrocarbon (7, 11-HD) acts both as an aphrodisiac to males of D. melanogaster and also as a key compound causing males of other closely related species in the genus to reject her," said Tristram Wyatt, an evolutionary biologist at the University of Oxford. "It's surprising at first sight, but perhaps it's another example of evolution resulting in simple solutions, two effects for one."
Billeter's study isn't the first time that the pheromone-less flies have been shown to be hyperattractive. Fabrice Savarit from the Universite Paris Sud and colleagues reported similar results in 1999. "One of the main differences between our study and Billeter's is his team was able to cleanly get rid of oenocytes," said Matthew Cobb, an evolutionary neurobiologist at the University of Manchester in England and coauthor of the 1999 study. "We produced pheromone-less flies in a roundabout way by overexpressing the UAS-tra transgene. Billeter's methodology is much more precise and reproducible." Billeter's study was also able to produce pheromone-less male flies, something Cobb's team failed to do.
Wyatt agreed, noting that the "blank canvas" flies will be invaluable "in further researching the neural circuits involved in sex and species recognition in these flies."
Cobb also noted that while hydrocarbons excreted by oenocytes may not initiate mating in flies, other pheromones might. In their 1999 study, Savarit and his colleagues noticed there was still a small amount of pheromones on their supposedly hydrocarbon-less female flies. Cobb noticed a similar trend in Billeter's data. "It seems even after they wiped out all the oenocytes in flies, there is a tiny -- we're talking less than 10 millivolts -- but significant amount of hydrocarbons still present," he said. "These might be ancestral pheromones, or not, but either way it is very intriguing."
======= =========== ======== ========== ====== ========
Pheromones may not initiate sexual attraction and mating, as commonly believed, new research suggests. Instead, the chemical signals may help flies distinguish between different genders and species while choosing a mate, researchers report in this week's issue of Nature.
This is the first time a study has deciphered the chemical dialogue happening between flies as they mate," said Nicolas Gompel, a geneticist at the Institut de Biologie du Developpement de Marseille-Luminy in France, who was not involved with the research but wrote an accompanying commentary on the paper. "The research challenges the common belief that pheromones are essential to initiate courtship... and suggests that instead, [they] play a significant role in mate identification and selection."
Scientists have long understood that pheromones, hydrocarbons produced by an animal or insect that trigger reactions in another individual, play a role in mating. But they've been unable to identify the role of individual pheromones because the hydrocarbons are often secreted as blends, comprised of up to 30 molecules, and function in conjunction with other signals. In order to study individual pheromones, Jean-Christophe Billeter from the University of Toronto at Mississauga and his colleagues genetically engineered adult Drosophila melanogaster without oenocytes, cells that secret hydrocarbons. The oenocyte-less flies were "blank slates," said Joel Levine, a geneticist from the University of Toronto and coauthor of the study, allowing the team to imprint one pheromone at a time.
Because pheromones have been generally believed to stimulate mating, Billeter and his colleagues expected that flies lacking hydrocarbons would be sexually unappealing to males. To their surprise, quite the opposite happened: wild-type males were hyperattracted to oenocyte-less flies. The wild-type males also ignored gender, choosing to mate with both unscented males and females over other wild-types. These results led the researchers to conclude that pheromones may not stimulate mating, but may instead act to slow down male mating attempts to allow the female to assess her partner's suitability. They also concluded that hydrocarbons help flies distinguish between sexes.
Billeter and his colleagues then tested the effect of individual pheromones on mate selection and copulation attempts. Researchers treated unscented D. melanogaster with wild-type levels of cVA, a hydrocarbon males are known to coat on females to deter further mating attempts. As expected, cVA effectively created a "chemical chastity belt," said Gompel.
Researchers then treated unscented flies with 7,11-heptacosadiene (7,11-HD), a pheromone thought to act as an aphrodisiac for flies. Although 7,11-HD alone did not stimulate additional mating attempts, when applied over cVA, it helped diminish the inhibiting effect of the compound, allowing females to broadcast their mating availability. The findings suggested that mating doesn't depend on just one pheromone relaying a message of availability, but instead on a complex mixture of attractive and aversive signals.
7,11-HD also seemed to act as a species barrier in mating. Unscented D. melanogaster females treated with the hydrocarbon attracted males of the same species, but deterred D. simulans and D. yakuba males.
"It's neat that one hydrocarbon (7, 11-HD) acts both as an aphrodisiac to males of D. melanogaster and also as a key compound causing males of other closely related species in the genus to reject her," said Tristram Wyatt, an evolutionary biologist at the University of Oxford. "It's surprising at first sight, but perhaps it's another example of evolution resulting in simple solutions, two effects for one."
Billeter's study isn't the first time that the pheromone-less flies have been shown to be hyperattractive. Fabrice Savarit from the Universite Paris Sud and colleagues reported similar results in 1999. "One of the main differences between our study and Billeter's is his team was able to cleanly get rid of oenocytes," said Matthew Cobb, an evolutionary neurobiologist at the University of Manchester in England and coauthor of the 1999 study. "We produced pheromone-less flies in a roundabout way by overexpressing the UAS-tra transgene. Billeter's methodology is much more precise and reproducible." Billeter's study was also able to produce pheromone-less male flies, something Cobb's team failed to do.
Wyatt agreed, noting that the "blank canvas" flies will be invaluable "in further researching the neural circuits involved in sex and species recognition in these flies."
Cobb also noted that while hydrocarbons excreted by oenocytes may not initiate mating in flies, other pheromones might. In their 1999 study, Savarit and his colleagues noticed there was still a small amount of pheromones on their supposedly hydrocarbon-less female flies. Cobb noticed a similar trend in Billeter's data. "It seems even after they wiped out all the oenocytes in flies, there is a tiny -- we're talking less than 10 millivolts -- but significant amount of hydrocarbons still present," he said. "These might be ancestral pheromones, or not, but either way it is very intriguing."
Subscribe to:
Posts (Atom)
