Search

Candida albicans is the most common fungal pathogen in humans, causing both debilitating mucosal infections and potentially life-threatening systemic infections. Until recently, C. albicans was thought to be strictly asexual, existing only as an obligate diploid. A cryptic mating cycle has since been uncovered in which diploid a and α cells undergo efficient cell and nuclear fusion, resulting in tetraploid a/α mating products. Whereas mating between a and α cells has been established (heterothallism), we report here two pathways for same-sex mating (homothallism) in C. albicans. First, unisexual populations of a cells were found to undergo autocrine pheromone signalling and same-sex mating in the absence of the Bar1 protease. In both C. albicans and Saccharomyces cerevisiae, Bar1 is produced by a cells and inactivates mating pheromone α, typically secreted by α cells. C. albicans Δbar1 a cells were shown to secrete both a and α mating pheromones; α-pheromone activated self-mating in these cells in a process dependent on Ste2, the receptor for α-pheromone. In addition, pheromone production by α cells was found to promote same-sex mating between wild-type a cells. These results establish that homothallic mating can occur in C. albicans, revealing the potential for genetic exchange even within unisexual populations of the organism. Furthermore, Bar1 protease has an unexpected but pivotal role in determining whether sexual reproduction can potentially be homothallic or is exclusively heterothallic. These findings also have implications for the mode of sexual reproduction in related species that propagate unisexually, and indicate a role for specialized sexual cycles in the survival and adaptation of pathogenic fungi. [ABSTRACT FROM AUTHOR]

The article discusses the research efforts of biologist Mike Russell who is attempting to recreate the conditions of early earth that resulted in the creation of life. His experimentation is designed to investigate his theories about the role of geology in the emergence of biological life. His experimentation is described, as is his perception of the role of methane and acetate in development of single-celled organisms. Russell's early work in pharmacy, geology, and mineral exploration are recounted.

The emergence of the ribosome constituted a pivotal step in the evolution of life. This event happened nearly four billion years ago, and any traces of early stages of ribosome evolution are generally thought to have completely eroded away. Surprisingly, a detailed analysis of the structure of the modern ribosome reveals a concerted and modular scheme of its early evolution. [ABSTRACT FROM AUTHOR]

The article focuses on the increase of human life expectancy, and the complexities of the ageing process. According to the author, the increase in human life expectancy has increased by several hours per day in various countries. The increase in life expectancy has affected the ageing process, a biological process that benefits from systems biology. Topics covered include nature of systems biology, diseases brought by age, and results of research on ageing. The author inferred that there are more things to discover in the problems of ageing.

The ‘RNA world’ hypothesis holds that during evolution the structural and enzymatic functions initially served by RNA were assumed by proteins, leading to the latter’s domination of biological catalysis. This progression can still be seen in modern biology, where ribozymes, such as the ribosome and RNase P, have evolved into protein-dependent RNA catalysts (‘RNPzymes’). Similarly, group I introns use RNA-catalysed splicing reactions, but many function as RNPzymes bound to proteins that stabilize their catalytically active RNA structure. One such protein, the Neurospora crassa mitochondrial tyrosyl-tRNA synthetase (TyrRS; CYT-18), is bifunctional and both aminoacylates mitochondrial tRNATyr and promotes the splicing of mitochondrial group I introns. Here we determine a 4.5-Å co-crystal structure of the Twort orf142-I2 group I intron ribozyme bound to splicing-active, carboxy-terminally truncated CYT-18. The structure shows that the group I intron binds across the two subunits of the homodimeric protein with a newly evolved RNA-binding surface distinct from that which binds tRNATyr. This RNA binding surface provides an extended scaffold for the phosphodiester backbone of the conserved catalytic core of the intron RNA, allowing the protein to promote the splicing of a wide variety of group I introns. The group I intron-binding surface includes three small insertions and additional structural adaptations relative to non-splicing bacterial TyrRSs, indicating a multistep adaptation for splicing function. The co-crystal structure provides insight into how CYT-18 promotes group I intron splicing, how it evolved to have this function, and how proteins could have incrementally replaced RNA structures during the transition from an RNA world to an RNP world. [ABSTRACT FROM AUTHOR]

Many high-throughput loss-of-function analyses of the eukaryotic cell cycle have relied on the unicellular yeast species Saccharomyces cerevisiae and Schizosaccharomyces pombe. In multicellular organisms, however, additional control mechanisms regulate the cell cycle to specify the size of the organism and its constituent organs. To identify such genes, here we analysed the effect of the loss of function of 70% of Drosophila genes (including 90% of genes conserved in human) on cell-cycle progression of S2 cells using flow cytometry. To address redundancy, we also targeted genes involved in protein phosphorylation simultaneously with their homologues. We identify genes that control cell size, cytokinesis, cell death and/or apoptosis, and the G1 and G2/M phases of the cell cycle. Classification of the genes into pathways by unsupervised hierarchical clustering on the basis of these phenotypes shows that, in addition to classical regulatory mechanisms such as Myc/Max, Cyclin/Cdk and E2F, cell-cycle progression in S2 cells is controlled by vesicular and nuclear transport proteins, COP9 signalosome activity and four extracellular-signal-regulated pathways (Wnt, p38βMAPK, FRAP/TOR and JAK/STAT). In addition, by simultaneously analysing several phenotypes, we identify a translational regulator, eIF-3p66, that specifically affects the Cyclin/Cdk pathway activity. [ABSTRACT FROM AUTHOR]

Sexual reproduction can lead to major conflicts between sexes and within genomes. Here we report an extreme case of such conflicts in the little fire ant Wasmannia auropunctata. We found that sterile workers are produced by normal sexual reproduction, whereas daughter queens are invariably clonally produced. Because males usually develop from unfertilized maternal eggs in ants and other haplodiploid species, they normally achieve direct fitness only through diploid female offspring. Hence, although the clonal production of queens increases the queen's relatedness to reproductive daughters, it potentially reduces male reproductive success to zero. In an apparent response to this conflict between sexes, genetic analyses reveal that males reproduce clonally, most likely by eliminating the maternal half of the genome in diploid eggs. As a result, all sons have nuclear genomes identical to those of their father. The obligate clonal production of males and queens from individuals of the same sex effectively results in a complete separation of the male and female gene pools. These findings show that the haplodiploid sex-determination system provides grounds for the evolution of extraordinary genetic systems and new types of sexual conflict. [ABSTRACT FROM AUTHOR]

Most animals reproduce until they die, but in humans, females can survive long after ceasing reproduction. In theory, a prolonged post-reproductive lifespan will evolve when females can gain greater fitness by increasing the success of their offspring than by continuing to breed themselves. Although reproductive success is known to decline in old age, it is unknown whether women gain fitness by prolonging lifespan post-reproduction. Using complete multi-generational demographic records, we show that women with a prolonged post-reproductive lifespan have more grandchildren, and hence greater fitness, in pre-modern populations of both Finns and Canadians. This fitness benefit arises because post-reproductive mothers enhance the lifetime reproductive success of their offspring by allowing them to breed earlier, more frequently and more successfully. Finally, the fitness benefits of prolonged lifespan diminish as the reproductive output of offspring declines. This suggests that in female humans, selection for deferred ageing should wane when one's own offspring become post-reproductive and, correspondingly, we show that rates of female mortality accelerate as their offspring terminate reproduction. [ABSTRACT FROM AUTHOR]

Proves that a population of independent, random walking organisms, brownian bugs, reproducing by binary division and dying at constant rates, spontaneously aggregates. Causes of clustering among organisms; Methodology used for the simulation of the brownian bug model; Description of the brownian bug process.

The human brain stands out among mammals by being unusually large. The expensive-tissue hypothesis explains its evolution by proposing a trade-off between the size of the brain and that of the digestive tract, which is smaller than expected for a primate of our body size. Although this hypothesis is widely accepted, empirical support so far has been equivocal. Here we test it in a sample of 100 mammalian species, including 23 primates, by analysing brain size and organ mass data. We found that, controlling for fat-free body mass, brain size is not negatively correlated with the mass of the digestive tract or any other expensive organ, thus refuting the expensive-tissue hypothesis. Nonetheless, consistent with the existence of energy trade-offs with brain size, we find that the size of brains and adipose depots are negatively correlated in mammals, indicating that encephalization and fat storage are compensatory strategies to buffer against starvation. However, these two strategies can be combined if fat storage does not unduly hamper locomotor efficiency. We propose that human encephalization was made possible by a combination of stabilization of energy inputs and a redirection of energy from locomotion, growth and reproduction. [ABSTRACT FROM AUTHOR]

Sound communication plays a vital role in frog reproduction, in which vocal advertisement is generally the domain of males. Females are typically silent, but in a few anuran species they can produce a feeble reciprocal call or rapping sounds during courtship. Males of concave-eared torrent frogs (Odorrana tormota) have demonstrated ultrasonic communication capacity. Although females of O. tormota have an unusually well-developed vocal production system, it is unclear whether or not they produce calls or are only passive partners in a communication system dominated by males. Here we show that before ovulation, gravid females of O. tormota emit calls that are distinct from males’ advertisement calls, having higher fundamental frequencies and harmonics and shorter call duration. In the field and in a quiet, darkened indoor arena, these female calls evoke vocalizations and extraordinarily precise positive phonotaxis (a localization error of <1°), rivalling that of vertebrates with the highest localization acuity (barn owls, dolphins, elephants and humans). The localization accuracy of O. tormota is remarkable in light of their small head size (interaural distance of <1 cm), and suggests an additional selective advantage of high-frequency hearing beyond the ability to avoid masking by low-frequency background noise. [ABSTRACT FROM AUTHOR]

The evolution of helping, in which some individuals forfeit their own reproduction and help others to reproduce, is a central problem in evolutionary biology. Recently proposed insurance-based mechanisms rely on a pre-existing life history with a long period of offspring dependency relative to the short life expectancies of adult carers: a lone mother's offspring are doomed if she dies young, whereas after a helper dies, other group members can finish rearing the offspring. A critical question, however, is how this life history could evolve in ancestral non-social populations, as offspring survival would then depend on a single, short-lived carer. Here, we resolve this paradox by focusing on the extended parental care inherent in prolonged dependency. We show experimentally that in non-social wasps, extended care can significantly reduce the impact of interspecific parasites. Under extended care, offspring are less vulnerable by the time they are exposed to parasites, and costs of parasitism are reduced because mothers have the option to terminate investment in failing offspring. By experimentally simulating aspects of extended care in a species where it is lacking, we demonstrate that neither benefit requires specialized behaviour. Such benefits could therefore offset the disadvantage of prolonged dependency in non-social species, thereby facilitating the evolution of helping. [ABSTRACT FROM AUTHOR]

Focuses on a study which confirmed a prediction that survival of the flattest may be as important as survival of the fittest at high mutation rates among digital organisms. Description of digital organisms; Methodology; Results; Implications of the study.

Recent finds demonstrate that internal fertilization and viviparity (live birth) were more widespread in the Placodermi, an extinct group of armoured fishes, than was previously realized. Placoderms represent the sister group of the crown group jawed vertebrates (Gnathostomata), making their mode(s) of reproduction potentially informative about primitive gnathostome conditions. An ossified pelvic fin basipterygium discovered in the arthrodire Incisoscutum ritchiei was hypothesized to be identical in males and females, with males presumed to have an additional cartilaginous element or series forming a clasper. Here we report the discovery of a completely ossified pelvic clasper in Incisoscutum ritchiei (WAM 03.3.28) which shows that this interpretation was incorrect: the basipterygium described previously is in fact unique to females. The male clasper is a slender rod attached to a square basal plate that articulates directly with the pelvis. It carries a small cap of dermal bone covered in denticles and small hooks that may be homologous with the much larger dermal component of the ptyctodont clasper. [ABSTRACT FROM AUTHOR]

The article discusses research pertaining to the emergence of sustained life on Earth. Conventional theories on this subject postulate that any life existing on the planet’s surface was eradicated 100 million years after its formation due to the impact of lunar debris such as asteroids during a period known as the late heavy bombardment (LHB). While this theory has used the lineage of life stemming from prokaryotic and eukaryotic life, as well as the discovery of zircons in ancient rocks, to support its legitimacy, the present study suggests that these criteria are incorrect. Using numerical models of impact-generated heat in the Earth’s crust, the researchers posit that only 37% of the Earth’s surface was sterilized in the LHB.

This article reports that when it comes to searching for life on other worlds, the U.S. National Aeronautics and Space Administration seems determined to follow the water. Water is a terrible solvent for life, according to chemist Steven Benner of the University of Florida in Gainesville. Benner is one of a number of biochemists, planetary scientists and philosophers who are trying to find out whether water is in some sense fine-tuned for life. The notion of redesigning life's chemistry has become central to the emerging discipline of synthetic biology, which has among its long-term objectives the aim of creating entire cells from scratch, perhaps with a different chemical basis from that of existing organisms.

Self-reproduction is central to biological life for long-term sustainability and evolutionary adaptation. Although these traits would also be desirable in many engineered systems, the principles of self-reproduction have not been exploited in machine design. Here we create simple machines that act as autonomous modular robots and are capable of physical self-reproduction using a set of cubes. [ABSTRACT FROM AUTHOR]

Discusses the implication of gene replication in the evolution of life science. Insight on the process of the RNA to reproduce complementary molecules; Idea on the role of RNA in the interaction with amino acids to synthesized protein; View on the application of gene selection to catalyze a chemical reaction to gene's replication.

The world has creatures that breathe iron and uranium, using these elements in the same way as people use oxygen. Others thrive in the equivalents of hot sulphuric acid or floor stripper, and others again live in solid rock. In terms of biomass, the single most For all of the marvels in biodiversity's new bestiary are invisible. Biodiversities include phylogenetic diversity, metabolic diversity, environmental diversity, and morphological diversity. This neglect of the invisible world is no longer any more acceptable.

In thinking about the evolution of cooperative behavior, there is one main stumbling block that cooperative individuals can be exploited by defectors, who benefit from cooperation while avoiding the costs that it entails. Solutions to this problem typically find ways for cooperative individuals to interact with one another more often than they would purely by chance. There are two basic ways in which this can happen. One involves the population having a spatial structure with local reproduction and dispersal, so that neighbors of a cooperative individual are themselves more likely to be cooperative.

Reports on results of a study by Lahdenpera and colleagues which showed that a grandmother has a beneficial effect on the reproductive success of her children and the survival of her grandchildren. Evolutionary importance of human longevity; Increases in life expectancy reflecting reductions in infant and juvenile mortality; Mammalian life histories.

Systems biology aims to predict the behaviour of an organism in nearly any situation. Investigators commonly assume that scientists with a quantitative background will fare better in systems biology. A systems biologist has to be able to understand two languages, the language of mathematics and that of biology. Therefore, Biologists eager to join the field need experience in mathematics or physics The greatest concentration of jobs for systems biology is in universities, or in institutes that straddle the line between academia and industry.

Focuses on the Gaia hypothesis. Constancy of the Earth's chemically unstable atmosphere; Origins of and predictions from Gaia; Discovery of plausible control mechanisms; Evolution of organisms and their environment as a single self-regulating systems.

Discusses the efficacy of calorie restriction (CR) in increasing the lifespan of species. Assumption on the mechanism by which CR delays aging; Results of a study on the effect of CR on the life span of yeast.

The article presents information published in the journal including existence of life on Earth and council of the Senate of theUniversity of Cambridge offering vast range of facility to the student and faculty of University of Louvain, 50 and 100 years ago respectively.

An interview with Patrick Phillips, an evolutionary biologist at the University of Oregon in Eugene, Oregon, is presented. When asked about his reason of being interested in sexual reproduction, he refers sexual reproduction as the major feature of life on Earth. Phillips stresses on the thing the makes the C. elegans an ideal model system for studying sexual reproduction. Moreover, he cites way he test the adaptation of the theory.

The article reports an insight into amber with the use of propagation-phase contrast microradiography. Through synchrotron X-ray imaging technique, French paleontologists at the University of Rennes and the European Synchrotron Radiation Facility in Grenoble were able to make the organisms like spider and conifer branch hidden by the fossilized tree resin for around 100 million years visible. They even produced a series of spectacular three-dimensional images and examined around two kilograms of opaque amber from mid-Cretaceous sites in southwestern France.

Reports on the meeting of researchers to discuss methods of handling the new lines of genetically modified mice in Bar Harbor, Maine. Launch of the first large-scale program to generate mutants; Creation of an alliance to share information through a single website; Exploration of mice mutant resources.

Focuses on researchers' failure to confirm biochemical signs of life in so called nanobacteria. Difficulties inherent in the microbial and biochemical analysis of the pathogenic microorganisms due to coats of heavy hydroxyapatite; Claim that the particles' self-propagation and morphology can be explained in terms of microcrystallization.

Focuses on developments concerning scientific research about lifespan extension. Popular beliefs about activities that extend lifespan; World Bank and World Health Organization's contention that the most powerful lifespan-extending technologies are still far off.