Mutualism: Fungus Found That Needs Bacteria In Cytoplasm To Reproduce
ScienceDaily (Apr. 6, 2007) — Endosymbiotic relationships--in which one organism lives within another--are striking examples of mutualism, and can often significantly shape the biology of the participant species.
In new findings that highlight the extent to which a host organism can become dependent on its internal symbiont, researchers have identified a case in which the reproduction of a fungus has become dependent on bacteria that live within its cytoplasm. The findings, which appear online in the journal Current Biology on April 5th, are reported by Laila Partida and Christian Hertweck from the Leibniz Institute for Natural Product Research and Infection Biology in Jena, Germany.
The particular partnership under study is the symbiosis of the fungus Rhizopus microsporus and Burkholderia bacteria that live within its cells. The two species effectively team up to break down young rice plants for their nutrients, causing a plant disease known as rice seedling blight. Past work from the research group had revealed that the Burkholderia bacteria play a critical role in the virulence of the fungus against rice seedlings: The bacteria produce a plant poison known as rhizoxin, which has been shown to be the causative agent in rice seedling blight.
The researchers now report a second, striking benefit conferred on the fungus by its intracellular symbiont. When the bacteria are eliminated from the fungus with antibiotic treatment, the fungal cells are no longer able to form spores, suggesting that the bacterial symbiont is in fact required for this mode of fungal reproduction. Spore formation in fungi is a universal process that allows the rapid distribution of fungal cells. The new findings appear to represent the first known case in which spore formation--also known as vegetative reproduction--depends on the presence of another organism.
The researchers found that when both organisms were brought together to re-establish the symbiosis, sporulation was restored in the fungus.
In collaboration with researchers at the Leibniz Institute for Age Research, Jena, the team also made progress in understanding how the endosymbiotic bacteria influence reproduction by their host. Using a laser gun to introduce Burkholderia that had been specially labeled with a marker known as green fluorescent protein, the researchers were able to detect the bacteria within both mycelium--the vegetative portion of the fungus--and fungal spores.
On the basis of their findings, the authors conclude that the symbiont-dependent spore formation they observe is a means to maintain the symbiosis between the two species. Although the fungus has lost control over its reproduction, the endofungal bacteria in return provide a highly potent toxin for defending the habitat and accessing nutrients from decaying plants.
Partida-Martinez et al.: "Endosymbiont-Dependent Host Reproduction Maintains Bacterial-Fungal Mutualism." Publishing in Current Biology 17, 1--5, May 1, 2007. DOI 10.1016/j.cub.2007.03.039.
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Adapted from materials provided by Cell Press, via EurekAlert!, a service of AAAS.
Sunday, June 29, 2008
Fungi Respond To Climate Change
ScienceDaily (Apr. 25, 2007) — Climate change is dramatically altering the growing patterns of mushrooms, toadstools and other fungi, new research has found.
There are around 18,000 different species of fungi in the UK -- three times as many as all plants put together. They provide vital ecosystem services for the welfare of native trees and other plants, and are the natural recyclers of the planet, but until now their response to global climate change has not been examined.
A team from Cardiff University’s School of Biosciences working on a project led by Royal Holloway, University of London and with the Natural Environment Research Council Centre for Ecology and Hydrology studied more than 52,000 fungal fruiting records from nearly 1,400 localities collected in southern England between 1950 - 2005.
The study found that fungi are fruiting significantly earlier and for a longer period than ever before. In the 1950s fungi fruited over a period of around 33 days but this has more than doubled to nearly 75 days in the current decade.
Professor Lynne Boddy, Cardiff School of Biosciences said: "The increase in the overall fruiting period is dramatic, and much higher than equivalent spring data reported for plants, insects or birds."
The study found that the alteration in fungal fruiting mirrors changes in British temperatures that have occurred since 1975. The increase in late summer temperatures and autumnal rains has caused early season species to fruit earlier and late season species to continue to fruit later. Furthermore, climate warming seems to have caused significant numbers of species to begin fruiting in spring as well as autumn, suggesting increases in decay rates in forests.
--------------------------------------------------------------------------------
Adapted from materials provided by Cardiff University.
ScienceDaily (Apr. 25, 2007) — Climate change is dramatically altering the growing patterns of mushrooms, toadstools and other fungi, new research has found.
There are around 18,000 different species of fungi in the UK -- three times as many as all plants put together. They provide vital ecosystem services for the welfare of native trees and other plants, and are the natural recyclers of the planet, but until now their response to global climate change has not been examined.
A team from Cardiff University’s School of Biosciences working on a project led by Royal Holloway, University of London and with the Natural Environment Research Council Centre for Ecology and Hydrology studied more than 52,000 fungal fruiting records from nearly 1,400 localities collected in southern England between 1950 - 2005.
The study found that fungi are fruiting significantly earlier and for a longer period than ever before. In the 1950s fungi fruited over a period of around 33 days but this has more than doubled to nearly 75 days in the current decade.
Professor Lynne Boddy, Cardiff School of Biosciences said: "The increase in the overall fruiting period is dramatic, and much higher than equivalent spring data reported for plants, insects or birds."
The study found that the alteration in fungal fruiting mirrors changes in British temperatures that have occurred since 1975. The increase in late summer temperatures and autumnal rains has caused early season species to fruit earlier and late season species to continue to fruit later. Furthermore, climate warming seems to have caused significant numbers of species to begin fruiting in spring as well as autumn, suggesting increases in decay rates in forests.
--------------------------------------------------------------------------------
Adapted from materials provided by Cardiff University.
Secrets Of Cooperation Between Trees And Fungi Revealed
Secrets Of Cooperation Between Trees And Fungi Revealed
ScienceDaily (Mar. 6, 2008) — Plants gained their ancestral toehold on dry land with considerable help from their fungal friends. Now, millennia later, that partnership is being exploited as a strategy to bolster biomass production for next generation biofuels. The genetic mechanism of this kind of symbiosis, which contributes to the delicate ecological balance in healthy forests, also provides insights into plant health that may enable more efficient carbon sequestration and enhanced phytoremediation, using plants to clean up environmental contaminants.
These prospects stem from the genome analysis of the symbiotic fungus Laccaria bicolor, generated by the U.S. Department of Energy Joint Genome Institute (DOE JGI) and collaborators from INRA, the National Institute for Agricultural Research in Nancy, France, and published March 6 in the journal Nature. This international team effort also involved contributions from 16 institutions, including Oak Ridge National Laboratory; Ghent University, Belgium; Lund University, Sweden; Goettingen University, Germany; CNRS-Aix-Marseille University, France; Nancy University, France; and the University of Alabama, Huntsville.
In a manner of speaking, trees are the lungs of the earth. They draw CO2 from the atmosphere and convert it into sugars, which then become a source of energy. In the process they breathe O2 back into the atmosphere. This "green" production of biomass -- trees account for 90% of the planet's land-based biomass -- is a major influence on the health of our planet.
Trees' ability to generate large amounts of biomass or store carbon is underpinned by their interactions with soil microbes known as mycorrhizal fungi, which excel at procuring necessary, but scarce, nutrients such as phosphate and nitrogen. Most of these nutrients are transferred to the growing tree. When Laccaria bicolor establishes a partnership with plant roots, a mycorrhizal root is created. The fungus within the root is protected from competition with other soil microbes and gains preferential access to carbohydrates within the plant. Thus, the mutualistic relationship is established.
"Forests around the world rely on the partnership between plant roots and soil fungi and the environment they create, the rhizosphere," said Eddy Rubin, DOE JGI Director. "The Laccaria genome represents a valuable resource, the first of a series of tree community genomics projects to have passed through our production sequencing line. These community resources promise to advance a systems approach to forest genomics."
Rubin indicates that by using DNA sequence to survey the forest ecosystem, from the plants to symbiotic and pathogenic fungi, researchers can ultimately optimize the conditions under which a biomass plantation would thrive. "We now have the opportunity to gain fundamental insights into plant development and growth as related to their intimate interaction which symbiotic fungi. These insights will lead to bolstered biomass productivity and improved forests."
Laccaria bicolor occurs frequently in the birch, fir, and pine forests of North America and is a common symbiont of Populus, the poplar tree whose genome was determined by the JGI in 2006 The analysis of the 65-million-base Laccaria genome, the largest fungal genome sequenced to date, yielded 20,000 predicted protein-encoding genes, almost as many as in the human genome. In sifting through these data, researchers have discovered many unexpected features, including an arsenal of small secreted proteins (SSPs), several of which are only expressed in tissues associated with symbiosis. The most prominent SSP accumulates in the extending hyphae, the tips of the fungus that colonize the roots of the host plant.
"We believe that the proteins specific to this host/fungus interface play a decisive role in the establishment of symbiosis," said Francis Martin, the Nature study's lead author. This genome exploration led Martin and his CNRS-Marseille University and DOE JGI colleagues to the unexpected observation that the genome of Laccaria lacks the enzymes involved in degradation of the carbohydrate polymers of plant cell walls but maintains the ability to degrade non-plant cell walls, which may account for Laccaria's protective capacity. These observations point towards the dual life that mycorrhizal fungi like Laccaria possess, that is, the ability to grow in soil fending off pathogens and using decaying organic matter while serving as a custodian of living plant roots.
The genome, Martin said, shows a large number of new and expanded gene families compared with other fungi. Many of these families are involved in signaling and other processes that drive the complex transition between two distinct lifestyles of Laccaria: the benign saprotroph, able to use decaying matter of animal and bacterial origins, versus the symbiont, living in mutually profitable harmony with plant roots.
The team also discovered new classes of genes that may be candidates for the complex communication that must occur between the players in the host/plant subsoil arena during fungal development. They report that fungi play a critical role in plant nutrient use efficiency by translocating nutrients and water captured in soil pores inaccessible to roots of the host plant.
"The Laccaria genome sequence, its analysis, associated genomics, and bioinformatics tools provide an unprecedented opportunity to identify the key components of organism-environment interactions that modulate ecosystem responses to global change and increased nutrient input needed for faster growth, said Martin. "By examining and manipulating patterns of gene expression, we can identify the genetic control points that regulate plant growth and plant-mutualist response in an effort to better understand how these interactions control ecosystem function."
Mycorrhizae are critical elements of the terrestrial ecosystems, Martin said, since approximately 85 percent of all plant species, including trees, are dependent on such interactions to thrive. Mycorrhizae significantly improve photosynthetic carbon assimilation by plants.
"Host trees like Populus are able to harness this formidable web of mycorrhizal hyphae that permeates the soil and leaf litter and coax a relationship for their mutual nutritional benefit," said co-author DOE JGI and Oak Ridge National Laboratory researcher Jerry Tuskan. "This process is absolutely critical to the success of the interactions between the fungi and the roots of the host plant so that an equitable exchange of nutrients can be achieved." The DOE JGI and its collaborators have now embarked on characterizing several other poplar community symbionts that will provide a more comprehensive understanding of the biological community of the poplar forest. These include Glomus, a second plant symbiotic fungus, Melampsora, a leaf pathogen, and several plant endophytes, bacteria and fungi that live inside the poplar tree.
"DOE JGI's expanding portfolio of community genomes provides the researchers with a set of resources that can be used to map out the processes by which fungi colonize wood and soil litter. These fungi interact with living plants within their ecosystem in order to perform vital functions in the carbon and nitrogen cycles that are so fundamental to sustainable plant growth," said Tuskan.
The DOE JGI Laccaria effort was led by Igor Grigoriev. Other authors include Andrea Aerts, Erika Lindquist, Asaf Salamov, Harris Shapiro, Peter Brokstein, Chris Detter (Los Alamos National Laboratory), the DOE JGI Production Genomics Facility sequencing team led by Susan Lucas, and partners at the Stanford Human Genome Center, Jane Grimwood and Jeremy Schmutz.
--------------------------------------------------------------------------------
Adapted from materials provided by DOE/Joint Genome Institute.
ScienceDaily (Mar. 6, 2008) — Plants gained their ancestral toehold on dry land with considerable help from their fungal friends. Now, millennia later, that partnership is being exploited as a strategy to bolster biomass production for next generation biofuels. The genetic mechanism of this kind of symbiosis, which contributes to the delicate ecological balance in healthy forests, also provides insights into plant health that may enable more efficient carbon sequestration and enhanced phytoremediation, using plants to clean up environmental contaminants.
These prospects stem from the genome analysis of the symbiotic fungus Laccaria bicolor, generated by the U.S. Department of Energy Joint Genome Institute (DOE JGI) and collaborators from INRA, the National Institute for Agricultural Research in Nancy, France, and published March 6 in the journal Nature. This international team effort also involved contributions from 16 institutions, including Oak Ridge National Laboratory; Ghent University, Belgium; Lund University, Sweden; Goettingen University, Germany; CNRS-Aix-Marseille University, France; Nancy University, France; and the University of Alabama, Huntsville.
In a manner of speaking, trees are the lungs of the earth. They draw CO2 from the atmosphere and convert it into sugars, which then become a source of energy. In the process they breathe O2 back into the atmosphere. This "green" production of biomass -- trees account for 90% of the planet's land-based biomass -- is a major influence on the health of our planet.
Trees' ability to generate large amounts of biomass or store carbon is underpinned by their interactions with soil microbes known as mycorrhizal fungi, which excel at procuring necessary, but scarce, nutrients such as phosphate and nitrogen. Most of these nutrients are transferred to the growing tree. When Laccaria bicolor establishes a partnership with plant roots, a mycorrhizal root is created. The fungus within the root is protected from competition with other soil microbes and gains preferential access to carbohydrates within the plant. Thus, the mutualistic relationship is established.
"Forests around the world rely on the partnership between plant roots and soil fungi and the environment they create, the rhizosphere," said Eddy Rubin, DOE JGI Director. "The Laccaria genome represents a valuable resource, the first of a series of tree community genomics projects to have passed through our production sequencing line. These community resources promise to advance a systems approach to forest genomics."
Rubin indicates that by using DNA sequence to survey the forest ecosystem, from the plants to symbiotic and pathogenic fungi, researchers can ultimately optimize the conditions under which a biomass plantation would thrive. "We now have the opportunity to gain fundamental insights into plant development and growth as related to their intimate interaction which symbiotic fungi. These insights will lead to bolstered biomass productivity and improved forests."
Laccaria bicolor occurs frequently in the birch, fir, and pine forests of North America and is a common symbiont of Populus, the poplar tree whose genome was determined by the JGI in 2006 The analysis of the 65-million-base Laccaria genome, the largest fungal genome sequenced to date, yielded 20,000 predicted protein-encoding genes, almost as many as in the human genome. In sifting through these data, researchers have discovered many unexpected features, including an arsenal of small secreted proteins (SSPs), several of which are only expressed in tissues associated with symbiosis. The most prominent SSP accumulates in the extending hyphae, the tips of the fungus that colonize the roots of the host plant.
"We believe that the proteins specific to this host/fungus interface play a decisive role in the establishment of symbiosis," said Francis Martin, the Nature study's lead author. This genome exploration led Martin and his CNRS-Marseille University and DOE JGI colleagues to the unexpected observation that the genome of Laccaria lacks the enzymes involved in degradation of the carbohydrate polymers of plant cell walls but maintains the ability to degrade non-plant cell walls, which may account for Laccaria's protective capacity. These observations point towards the dual life that mycorrhizal fungi like Laccaria possess, that is, the ability to grow in soil fending off pathogens and using decaying organic matter while serving as a custodian of living plant roots.
The genome, Martin said, shows a large number of new and expanded gene families compared with other fungi. Many of these families are involved in signaling and other processes that drive the complex transition between two distinct lifestyles of Laccaria: the benign saprotroph, able to use decaying matter of animal and bacterial origins, versus the symbiont, living in mutually profitable harmony with plant roots.
The team also discovered new classes of genes that may be candidates for the complex communication that must occur between the players in the host/plant subsoil arena during fungal development. They report that fungi play a critical role in plant nutrient use efficiency by translocating nutrients and water captured in soil pores inaccessible to roots of the host plant.
"The Laccaria genome sequence, its analysis, associated genomics, and bioinformatics tools provide an unprecedented opportunity to identify the key components of organism-environment interactions that modulate ecosystem responses to global change and increased nutrient input needed for faster growth, said Martin. "By examining and manipulating patterns of gene expression, we can identify the genetic control points that regulate plant growth and plant-mutualist response in an effort to better understand how these interactions control ecosystem function."
Mycorrhizae are critical elements of the terrestrial ecosystems, Martin said, since approximately 85 percent of all plant species, including trees, are dependent on such interactions to thrive. Mycorrhizae significantly improve photosynthetic carbon assimilation by plants.
"Host trees like Populus are able to harness this formidable web of mycorrhizal hyphae that permeates the soil and leaf litter and coax a relationship for their mutual nutritional benefit," said co-author DOE JGI and Oak Ridge National Laboratory researcher Jerry Tuskan. "This process is absolutely critical to the success of the interactions between the fungi and the roots of the host plant so that an equitable exchange of nutrients can be achieved." The DOE JGI and its collaborators have now embarked on characterizing several other poplar community symbionts that will provide a more comprehensive understanding of the biological community of the poplar forest. These include Glomus, a second plant symbiotic fungus, Melampsora, a leaf pathogen, and several plant endophytes, bacteria and fungi that live inside the poplar tree.
"DOE JGI's expanding portfolio of community genomes provides the researchers with a set of resources that can be used to map out the processes by which fungi colonize wood and soil litter. These fungi interact with living plants within their ecosystem in order to perform vital functions in the carbon and nitrogen cycles that are so fundamental to sustainable plant growth," said Tuskan.
The DOE JGI Laccaria effort was led by Igor Grigoriev. Other authors include Andrea Aerts, Erika Lindquist, Asaf Salamov, Harris Shapiro, Peter Brokstein, Chris Detter (Los Alamos National Laboratory), the DOE JGI Production Genomics Facility sequencing team led by Susan Lucas, and partners at the Stanford Human Genome Center, Jane Grimwood and Jeremy Schmutz.
--------------------------------------------------------------------------------
Adapted from materials provided by DOE/Joint Genome Institute.
Self-fertility In Fungi: The Secrets Of 'DIY Reproduction'
Self-fertility In Fungi: The Secrets Of 'DIY Reproduction'
ScienceDaily (Aug. 17, 2007) — Research from The University of Nottingham sheds new light on a fascinating phenomenon of the natural world — the ability of some species to reproduce sexually without a partner.
Scientists have been trying to determine how individuals of a key fungus, Aspergillus nidulans, are able to have sex without the need for a partner.
In new findings published in the journal Current Biology on August 2, they reveal that the fungus has evolved to incorporate the two different sexes into the same individual.
This means that when sex occurs the fungus activates its internal sexual machinery and in essence 'mates with itself' to produce new offspring, rather than bypassing the sexual act.
This is a significant discovery as it helps scientists to understand how fungi reproduce in general. Fungi can cause health problems in humans and other serious animal and plant diseases, but are also useful as sources of pharmaceuticals and food products.
The long-term aim of the research is to be able to manipulate fungal sex to our own advantage, to prevent disease and help produce better strains for use in the food and biotech industries.
Dr Paul Dyer, of the School of Biology, was lead author of the study. He said: “When we think of sex in the animal world we normally associate it with males and females attracting each other and then coming together for the sexual act.”
“But things are different in the fungal and plant kingdoms, where a lot of species are 'self fertile'. This means that they are able to have sex to produce spores and seeds without the need for a compatible partner. Our findings show that Aspergillus nidulans provides a true example of 'DIY sex'.”
Self-fertilisation is thought to have developed in some plant and fungal species as a response to a scarcity of compatible mating partners. It also allows species to maintain a combination of genes — called a genotype — that is well adapted to surviving in a certain environment.
Aspergillus nidulans is often used as a model organism for scientists studying a wide range of subjects including basic genetic problems that are also applicable to humans, including recombination, DNA repair and cell metabolism.
The work was supported by a grant from the Biotechnology and Biological Sciences Research Council (BBSRC) and also involved researchers at Northern Illinois University and CNRS in France.
--------------------------------------------------------------------------------
Adapted from materials provided by University of Nottingham.
ScienceDaily (Aug. 17, 2007) — Research from The University of Nottingham sheds new light on a fascinating phenomenon of the natural world — the ability of some species to reproduce sexually without a partner.
Scientists have been trying to determine how individuals of a key fungus, Aspergillus nidulans, are able to have sex without the need for a partner.
In new findings published in the journal Current Biology on August 2, they reveal that the fungus has evolved to incorporate the two different sexes into the same individual.
This means that when sex occurs the fungus activates its internal sexual machinery and in essence 'mates with itself' to produce new offspring, rather than bypassing the sexual act.
This is a significant discovery as it helps scientists to understand how fungi reproduce in general. Fungi can cause health problems in humans and other serious animal and plant diseases, but are also useful as sources of pharmaceuticals and food products.
The long-term aim of the research is to be able to manipulate fungal sex to our own advantage, to prevent disease and help produce better strains for use in the food and biotech industries.
Dr Paul Dyer, of the School of Biology, was lead author of the study. He said: “When we think of sex in the animal world we normally associate it with males and females attracting each other and then coming together for the sexual act.”
“But things are different in the fungal and plant kingdoms, where a lot of species are 'self fertile'. This means that they are able to have sex to produce spores and seeds without the need for a compatible partner. Our findings show that Aspergillus nidulans provides a true example of 'DIY sex'.”
Self-fertilisation is thought to have developed in some plant and fungal species as a response to a scarcity of compatible mating partners. It also allows species to maintain a combination of genes — called a genotype — that is well adapted to surviving in a certain environment.
Aspergillus nidulans is often used as a model organism for scientists studying a wide range of subjects including basic genetic problems that are also applicable to humans, including recombination, DNA repair and cell metabolism.
The work was supported by a grant from the Biotechnology and Biological Sciences Research Council (BBSRC) and also involved researchers at Northern Illinois University and CNRS in France.
--------------------------------------------------------------------------------
Adapted from materials provided by University of Nottingham.
Evolution Of The Sexes: What A Fungus Can Tell Us
Evolution Of The Sexes: What A Fungus Can Tell Us
ScienceDaily (Jan. 10, 2008) — Fungi don't exactly come in boy and girl varieties, but they do have sex differences. In fact, a new finding from Duke University Medical Center shows that some of the earliest evolved forms of fungus contain clues to how the sexes evolved in higher animals, including that distant cousin of fungus, the human.
A team lead by Joseph Heitman, M.D. has isolated sex-determining genes from one of the oldest known types of fungi, Phycomyces blakesleeanus, findings which appear in the Jan. 10 issue of Nature.
Fungi do not have entire sex chromosomes, like the familiar X and Y chromosomes that determine sexual identity in humans. Instead, they have sex determining sequences of DNA called "mating-type loci."
Mating-type loci have been found in a number of higher-level fungal species, and exhibit an unusual amount of diversity. These differences occur even among similar fungal species leading scientists to wonder how they evolved.
Heitman's group hypothesized that the sex-determining arrangement found in one of earliest forms of fungi might reveal the ancestral structure of mating-type loci, serving as a sort of molecular fossil.
"Fungi are good model systems for the evolution of human sexual differentiation because the genetic sequences responsible for sex are smaller versions of chromosomal sex-determining regions in people," Heitman said.
To identify the mating-type loci in Phycomyces, the researchers used a computer search to compare known mating-type loci in the genomes of other fungal lineages and then genetic mapping. "We employed a usual-suspects approach, comparing proteins between fungal types before identifying a candidate that appeared related in all lineages," says Heitman.
Within this stretch of DNA, they were able to isolate two versions of a gene that regulates mating, which they dubbed sexM, (sex minus) and sexP (sex plus). Strains of fungi with opposite versions of the sex genes are able to mate with each other.
Both versions of the gene, sexM and sexP, encode for a single protein called a high mobility group (HMG)-domain protein that leads to sex differentiation through an unknown process. This protein is very similar to one encoded by the human Y chromosome, called SRY, that when turned on leads a developing fetus to exhibit male characteristics. Heitman said this similarity suggests that HMG-domain proteins may mark the evolutionary beginnings of sex determination in both fungi and humans.
Heitman's team proposes that sexM and sexP were once the same gene that went through a mutation process called inversion. The new versions then evolved into two separate sex genes. The same process is most likely responsible for the evolution of the male Y chromosome, Heitman suggests.
Heitman hopes to next identify the sex region in another fungus, Rhizopus oryzae in order to better understand how HMG-domain proteins control sex determination in fungi. Rhizopus' genes can be cultured and chemically altered in a way that Phycomyces' sex genes can not.
"Rhizopus can be used to understand the influences of certain genes in lesser studied fungi much in the way we use mice to understand genetic effects in humans," explained Alexander Idnurm, Ph.D., the primary author on the study and recently appointed assistant professor at the University of Missouri-Kansas City.
Another troubling mystery for Heitman is that certain younger fungal species lack HMG-domain proteins. He proposes that these proteins have been replaced with alternative transcription factors, which are proteins that turn genes on and off.
--------------------------------------------------------------------------------
Adapted from materials provided by Duke University Medical Center.
ScienceDaily (Jan. 10, 2008) — Fungi don't exactly come in boy and girl varieties, but they do have sex differences. In fact, a new finding from Duke University Medical Center shows that some of the earliest evolved forms of fungus contain clues to how the sexes evolved in higher animals, including that distant cousin of fungus, the human.
A team lead by Joseph Heitman, M.D. has isolated sex-determining genes from one of the oldest known types of fungi, Phycomyces blakesleeanus, findings which appear in the Jan. 10 issue of Nature.
Fungi do not have entire sex chromosomes, like the familiar X and Y chromosomes that determine sexual identity in humans. Instead, they have sex determining sequences of DNA called "mating-type loci."
Mating-type loci have been found in a number of higher-level fungal species, and exhibit an unusual amount of diversity. These differences occur even among similar fungal species leading scientists to wonder how they evolved.
Heitman's group hypothesized that the sex-determining arrangement found in one of earliest forms of fungi might reveal the ancestral structure of mating-type loci, serving as a sort of molecular fossil.
"Fungi are good model systems for the evolution of human sexual differentiation because the genetic sequences responsible for sex are smaller versions of chromosomal sex-determining regions in people," Heitman said.
To identify the mating-type loci in Phycomyces, the researchers used a computer search to compare known mating-type loci in the genomes of other fungal lineages and then genetic mapping. "We employed a usual-suspects approach, comparing proteins between fungal types before identifying a candidate that appeared related in all lineages," says Heitman.
Within this stretch of DNA, they were able to isolate two versions of a gene that regulates mating, which they dubbed sexM, (sex minus) and sexP (sex plus). Strains of fungi with opposite versions of the sex genes are able to mate with each other.
Both versions of the gene, sexM and sexP, encode for a single protein called a high mobility group (HMG)-domain protein that leads to sex differentiation through an unknown process. This protein is very similar to one encoded by the human Y chromosome, called SRY, that when turned on leads a developing fetus to exhibit male characteristics. Heitman said this similarity suggests that HMG-domain proteins may mark the evolutionary beginnings of sex determination in both fungi and humans.
Heitman's team proposes that sexM and sexP were once the same gene that went through a mutation process called inversion. The new versions then evolved into two separate sex genes. The same process is most likely responsible for the evolution of the male Y chromosome, Heitman suggests.
Heitman hopes to next identify the sex region in another fungus, Rhizopus oryzae in order to better understand how HMG-domain proteins control sex determination in fungi. Rhizopus' genes can be cultured and chemically altered in a way that Phycomyces' sex genes can not.
"Rhizopus can be used to understand the influences of certain genes in lesser studied fungi much in the way we use mice to understand genetic effects in humans," explained Alexander Idnurm, Ph.D., the primary author on the study and recently appointed assistant professor at the University of Missouri-Kansas City.
Another troubling mystery for Heitman is that certain younger fungal species lack HMG-domain proteins. He proposes that these proteins have been replaced with alternative transcription factors, which are proteins that turn genes on and off.
--------------------------------------------------------------------------------
Adapted from materials provided by Duke University Medical Center.
Fungi Can Tell Us About The Origin Of Sex Chromosomes
Fungi Can Tell Us About The Origin Of Sex Chromosomes
ScienceDaily (Mar. 18, 2008) — Fungi do not have sexes, just so-called mating types. A new study shows that there are great similarities between the parts of DNA that determine the sex of plants and animals and the parts of DNA that determine mating types in certain fungi. This makes fungi interesting as new model organisms in studies of the evolutionary development of sex chromosomes.
In the plant and animal kingdoms there are individuals of different sexes, that is, bearers of either many tiny sex cells (males) or a few large ones (females). In the third eukaryote kingdom (organisms with DNA gathered in the cell nucleus), the fungi kingdom, there are no sexes but rather a simpler and more primitive system of different so-called mating types. These are distinguished by different variants of a few specific genes.
There are many ways to determine sex. In humans it is done by sex chromosomes. It is thought that this sex difference arose in the plant and animal kingdom from the simpler system of mating types and that this happened several times independently of each other throughout evolution. The change is believed to have happened with the inhibition of a step in the copying process in DNA, which led to two separate chromosomes. These then developed further over a long period of time.
"In humans, sex chromosomes are believed to have developed over the last 300 million years from a common 'proto-sex chromosome,'" says Hanna Johannesson, who directed the study.
The new study shows for the first time that even though fungi do not have sexes, there are many similarities between the parts of the genome that determine sex in plants and animals and the parts of the genome that control mating types in certain fungi. The research group specifically studied a spore sac fungus (Neurospora tetrasperma) and can show that the similarities are great, regarding both present-day structure and the way in which it arose.
"It's hard to study the evolution of sex chromosomes, partly because so many different and important sex-specific characters are tied to them. But much of this can be avoided if we use simpler systems, like fungi, as models."
This research was published in the journal PLoS March 17, 2008.
--------------------------------------------------------------------------------
Adapted from materials provided by Uppsala University, via EurekAlert!, a service of AAAS.
ScienceDaily (Mar. 18, 2008) — Fungi do not have sexes, just so-called mating types. A new study shows that there are great similarities between the parts of DNA that determine the sex of plants and animals and the parts of DNA that determine mating types in certain fungi. This makes fungi interesting as new model organisms in studies of the evolutionary development of sex chromosomes.
In the plant and animal kingdoms there are individuals of different sexes, that is, bearers of either many tiny sex cells (males) or a few large ones (females). In the third eukaryote kingdom (organisms with DNA gathered in the cell nucleus), the fungi kingdom, there are no sexes but rather a simpler and more primitive system of different so-called mating types. These are distinguished by different variants of a few specific genes.
There are many ways to determine sex. In humans it is done by sex chromosomes. It is thought that this sex difference arose in the plant and animal kingdom from the simpler system of mating types and that this happened several times independently of each other throughout evolution. The change is believed to have happened with the inhibition of a step in the copying process in DNA, which led to two separate chromosomes. These then developed further over a long period of time.
"In humans, sex chromosomes are believed to have developed over the last 300 million years from a common 'proto-sex chromosome,'" says Hanna Johannesson, who directed the study.
The new study shows for the first time that even though fungi do not have sexes, there are many similarities between the parts of the genome that determine sex in plants and animals and the parts of the genome that control mating types in certain fungi. The research group specifically studied a spore sac fungus (Neurospora tetrasperma) and can show that the similarities are great, regarding both present-day structure and the way in which it arose.
"It's hard to study the evolution of sex chromosomes, partly because so many different and important sex-specific characters are tied to them. But much of this can be avoided if we use simpler systems, like fungi, as models."
This research was published in the journal PLoS March 17, 2008.
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Adapted from materials provided by Uppsala University, via EurekAlert!, a service of AAAS.
Bread Mold Yields A Genome First For Filamentous Fungi; Neurospora’s 10,000 Genes Include RIPs That Limit New Genes
Bread Mold Yields A Genome First For Filamentous Fungi; Neurospora’s 10,000 Genes Include RIPs That Limit New Genes
ScienceDaily (Apr. 28, 2003) — ARLINGTON, Va. -- With more than 10,000 genes amid DNA strands of nearly 40 million base pairs, the first genome of a filamentous fungus has been sequenced through the cooperative efforts of a community of more than 70 scientists, culminating a two-year, $5 million effort supported by the National Science Foundation. The work is reported in this week's issue of Nature, which celebrates the 50th anniversary of that journal's publication of the structure of DNA.
At the center of this latest genetics achievement is a filamentous fungus, a bread mold, a life form easily overlooked in the shadow of the Human Genome Project. To biologists, however, it is Neurospora crassa, an organism of historic and enduring value as a model organism.
More than a decade before the structure of DNA was determined, two biologists focusing on Neurospora as a model genetic organism first established that genes provide the information for the creation of proteins. For their "one gene, one enzyme" hypothesis linking genes to biochemical function, the two scientists-- George Wells Beadle and Edward Lawri Tatum--received the Nobel Prize in 1941.
"The legacy of over 70 years of research, coupled with the availability of molecular and genetic tools, offers enormous potential for continued discovery," write the authors of the current Nature article. They call their genome sequence a "high quality draft," covering pretty much all but the 2 to 3 percent in "unusual genomic regions…that cannot be assembled readily with available techniques."
An organism's genome consists of the entire genetic code held in its DNA. With more than 5000 papers on Neurospora published in the past 30 years, having the genome now allows many previous biological studies to be seen in a new light.
Though initially billed as "not a research project, but a high throughput production effort," the sequencing effort nevertheless yielded new insights into light sensitivity, fungal growth, circadian rhythms, calcium-release mechanisms, and other basic cellular phenomena.
It also shed new light on the production of compounds called "secondary metabolites," such as pigments, antibiotics and toxins. The fungal world, with more than 250,000 species and inhabitants in every ecosystem on earth, produces a vast array of these small, bioactive compounds.
Fungi--slime molds and mushrooms among them--are used for food and for the production of industrial chemicals and enzymes. They also rot wood, damage fabric, obscure optics and, as pathogens, injure animals and plants.
Charting Neurospora's DNA sequence allowed scientists to examine a curious genetic mechanism unique to fungi known as repeat induced point mutation, or RIP. First discovered in Neurospora in the 1980s, the RIP process detects and mutates whole sections of DNA where it finds a duplication in the DNA, a condition that otherwise often leads to the creation of new genes. The authors suggest that "RIP has a powerful impact in suppressing the creation of these new genes or partial genes" and it may have "virtually arrested" the further evolution of Neurospora.
According to Maryanna Henkart, director for NSF's Division of Molecular and Cellular Biology, the evolution of the Neurospora sequencing effort itself has been driven by a sense of community among those who study the mold.
The first genome project on Neurospora began in 1995 under a five year NSF grant to the University of New Mexico to improve research opportunities for minorities. It involved 36 students preparing and sequencing the DNA of some specific genes. Most were Hispanic or Native American. The authors of the project's first paper included 17 undergraduates, several of whom are now with leading genome institutes.
"In 2000, the greater Neurospora community mobilized to find a way to get the complete genome sequence done," said Henkart. Teamed with Bruce Birren of the Whitehead Institute at Massachusetts Institute of Technology, they submitted an ambitious, ultimately successful, proposal.
Begun in September 2000, the project released its first batch of sequence data on Feb. 14, 2001, with additional segments subsequently released.
By its completion, it had involved collaborators from more than 30 universities and research groups, representing more than 10 U.S. states and six countries.
--------------------------------------------------------------------------------
Adapted from materials provided by National Science Foundation.
ScienceDaily (Apr. 28, 2003) — ARLINGTON, Va. -- With more than 10,000 genes amid DNA strands of nearly 40 million base pairs, the first genome of a filamentous fungus has been sequenced through the cooperative efforts of a community of more than 70 scientists, culminating a two-year, $5 million effort supported by the National Science Foundation. The work is reported in this week's issue of Nature, which celebrates the 50th anniversary of that journal's publication of the structure of DNA.
At the center of this latest genetics achievement is a filamentous fungus, a bread mold, a life form easily overlooked in the shadow of the Human Genome Project. To biologists, however, it is Neurospora crassa, an organism of historic and enduring value as a model organism.
More than a decade before the structure of DNA was determined, two biologists focusing on Neurospora as a model genetic organism first established that genes provide the information for the creation of proteins. For their "one gene, one enzyme" hypothesis linking genes to biochemical function, the two scientists-- George Wells Beadle and Edward Lawri Tatum--received the Nobel Prize in 1941.
"The legacy of over 70 years of research, coupled with the availability of molecular and genetic tools, offers enormous potential for continued discovery," write the authors of the current Nature article. They call their genome sequence a "high quality draft," covering pretty much all but the 2 to 3 percent in "unusual genomic regions…that cannot be assembled readily with available techniques."
An organism's genome consists of the entire genetic code held in its DNA. With more than 5000 papers on Neurospora published in the past 30 years, having the genome now allows many previous biological studies to be seen in a new light.
Though initially billed as "not a research project, but a high throughput production effort," the sequencing effort nevertheless yielded new insights into light sensitivity, fungal growth, circadian rhythms, calcium-release mechanisms, and other basic cellular phenomena.
It also shed new light on the production of compounds called "secondary metabolites," such as pigments, antibiotics and toxins. The fungal world, with more than 250,000 species and inhabitants in every ecosystem on earth, produces a vast array of these small, bioactive compounds.
Fungi--slime molds and mushrooms among them--are used for food and for the production of industrial chemicals and enzymes. They also rot wood, damage fabric, obscure optics and, as pathogens, injure animals and plants.
Charting Neurospora's DNA sequence allowed scientists to examine a curious genetic mechanism unique to fungi known as repeat induced point mutation, or RIP. First discovered in Neurospora in the 1980s, the RIP process detects and mutates whole sections of DNA where it finds a duplication in the DNA, a condition that otherwise often leads to the creation of new genes. The authors suggest that "RIP has a powerful impact in suppressing the creation of these new genes or partial genes" and it may have "virtually arrested" the further evolution of Neurospora.
According to Maryanna Henkart, director for NSF's Division of Molecular and Cellular Biology, the evolution of the Neurospora sequencing effort itself has been driven by a sense of community among those who study the mold.
The first genome project on Neurospora began in 1995 under a five year NSF grant to the University of New Mexico to improve research opportunities for minorities. It involved 36 students preparing and sequencing the DNA of some specific genes. Most were Hispanic or Native American. The authors of the project's first paper included 17 undergraduates, several of whom are now with leading genome institutes.
"In 2000, the greater Neurospora community mobilized to find a way to get the complete genome sequence done," said Henkart. Teamed with Bruce Birren of the Whitehead Institute at Massachusetts Institute of Technology, they submitted an ambitious, ultimately successful, proposal.
Begun in September 2000, the project released its first batch of sequence data on Feb. 14, 2001, with additional segments subsequently released.
By its completion, it had involved collaborators from more than 30 universities and research groups, representing more than 10 U.S. states and six countries.
--------------------------------------------------------------------------------
Adapted from materials provided by National Science Foundation.
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