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Guillaume F.,Institute of Integrative Biology | Otto S.P.,University of British Columbia
Genetics | Year: 2012

Pleiotropy is the property of genes affecting multiple functions or characters of an organism. Genes vary widely in their degree of pleiotropy, but this variation is often considered a by-product of their evolutionary history. We present a functional theory of how pleiotropy may itself evolve. We consider genes that contribute to two functions, where contributing more to one function detracts from allocation to the second function. We show that whether genes become pleiotropic or specialize on a single function depends on the nature of trade-offs as gene activities contribute to different traits and on how the functionality of these traits affects fitness. In general, when a gene product can perform well at two functions, it evolves to do so, but not when pleiotropy would greatly disrupt each function. Consequently, reduced pleiotropy should often evolve, with genes specializing on the trait that is currently more important to fitness. Even when pleiotropy does evolve, not all genes are expected to become equally pleiotropic; genes with higher levels of expression are more likely to evolve greater pleiotropy. For the case of gene duplicates, we find that perfect subfunctionalization evolves only under stringent conditions. More often, duplicates are expected to maintain a certain degree of functional redundancy, with the gene contributing more to trait functionality evolving the highest degree of pleiotropy. Gene product interactions can facilitate subfunctionalization, but whether they do so depends on the curvature of the fitness surface. Finally, we find that stochastic gene expression favors pleiotropy by selecting for robustness in fitness components. © 2012 by the Genetics Society of America.


Willi Y.,University of Neuchatel | Willi Y.,Institute of Integrative Biology
American Naturalist | Year: 2013

Outcrossing creates a venue for parental conflict. When one sex provides parental care to offspring fertilized by several partners, the nonproviding sex is under selection to maximally exploit the caring sex. The caring sex may counteradapt, and a coevolutionary arms race ensues. Genetic models of this conflict include the kinship theory of genomic imprinting (parent-of-origin-specific expression of maternal-care effectors) and interlocus conflict evolution (interaction between male selfish signals and female abatement). Predictions were tested by measuring the sizes of seeds produced by within-population crosses (diallel design) and between-population crosses in outcrossing and selfing populations of Arabidopsis lyrata. Within-population diallel crosses revealed substantial maternal variance in seed size in most populations. The comparison of betweenand within-population crosses showed that seeds were larger when pollen came from another outcrossing population than when pollen came from a selfing or the same population, supporting interlocus contest evolution between male selfish genes and female recognition genes. Evidence for kinship genomic imprinting came from complementary trait means of seed size in reciprocal between-population crosses independent of whether populations were predominantly selfing or outcrossing. Hence, both kinship genomic imprinting and interlocus contest are supported in outcrossing Arabidopsis, whereas only kinship genomic imprinting is important in selfing populations. © 2013 by The University of Chicago.


Pedersen A.B.,Institute of Evolutionary Biology and Center for Immunity | Fenton A.,Institute of Integrative Biology
Trends in Parasitology | Year: 2015

It has become increasingly clear that parasites can have significant impacts on the dynamics of wildlife populations. Recently, researchers have shifted from using observational approaches to infer the impact of parasites on the health and fitness of individuals to using antiparasite drug treatments to test directly the consequences of infection. However, it is not clear the extent to which these experiments work in wildlife systems, or whether the results of these individual-level treatment experiments can predict the population-level consequences of parasitism. Here, we assess the results of treatment experiments, laying out the benefits and limitations of this approach, and discuss how they can be used to improve our understanding of the role of parasites in wildlife populations. © 2015 The Authors.


Scientists at the University of Liverpool have tracked how microscopic organisms called cyanobacteria make use of internal protein “machines” to boost their ability to convert carbon dioxide into sugar during photosynthesis. With global food and energy security one of the greatest challenges of the 21st century, the new findings could help inform the design and engineering of new nanotechnologies to improve crop yields and biomass production. Cyanobacteria, often known as blue-green algae, are among the most abundant organisms in oceans and fresh water. They are similar to green plants because they can use the energy from sunlight to make their own food through photosynthesis. However, unique to cyanobacteria are intracellular structures called carboxysomes that allow them to convert carbon dioxide to sugar — a process known as carbon fixation — significantly more efficiently than many crops can. Carboxysomes are made of polyhedral protein shells and contain the enzymes required for the bacteria to fix carbon during the Calvin cycle stage of photosynthesis. Little is known about how these nanoscale “machines” are produced or how they are regulated to adjust to environmental changes, such as light intensity. In a new study, published in Plant Physiology, researchers from the University’s Institute of Integrative Biology attached fluorescent tags to carboxysomes and then used a fluorescence microscope to watch them in action within individual cells. By experimentally altering the amount of light available during cell growth the researchers observed how cyanobacteria regulate carbon fixation activity by changing the amount of carboxysomes in cells. The researchers also used chemical inhibitors that modify metabolism to monitor how this affects the distribution pattern of carboxysomes. They found that carboxysomes can either spread out or sit in the central line of the rod-shaped cell, depending on the redox states of electron transport pathways induced by the inhibitors. In collaboration with Dr. Steve Barrett from the University’s Department of Physics, the team developed a method to statistically analyze hundreds to thousands of bacterial cells from the microscope images. Co-author Dr. Fang Huang says, “It’s exciting that through this technique we can now monitor, in real time, how bacteria modulate carboxysomes to maximize their carbon-fixing capacity. Our findings also provide some new clues about the relationship between the positioning of carboxysomes and cell metabolism.” Carboxysomes are of interest to synthetic biologists and bioengineers, who hope to find ways to utilize their energy-boosting potential in food and biofuel production. Dr. Luning Liu, lead author of the research, says, “Introducing cyanobacterial carboxysomes into plant chloroplasts could potentially improve the efficiency of photosynthesis and thereby the biomass yields. “There’s still a lot we need to learn before their potential can be exploited. At this stage, we’re just starting to understand how these fascinating cellular machines work, and this study marks another important step forward in this process.” The project was funded by the Biotechnology and Biological Sciences Research Council (BBSRC) and a Royal Society University Research Fellowship.


With global food and energy security one of the greatest challenges of the 21st century, the new findings could help inform the design and engineering of new nanotechnologies to improve crop yields and biomass production. Cyanobacteria, often known as blue-green algae, are among the most abundant organisms in oceans and fresh water. They are similar to green plants because they can use the energy from sunlight to make their own food through photosynthesis. However, unique to cyanobacteria are intracellular structures called carboxysomes that allow them to convert carbon dioxide to sugar – a process known as carbon fixation – significantly more efficiently than many crops can. Carboxysomes are made of polyhedral protein shells and contain the enzymes required for the bacteria to fix carbon during the Calvin cycle stage of photosynthesis. Little is known about how these nano-scale 'machines' are produced or how they are regulated to adjust to environmental changes, such as light intensity. In a new study, published in Plant Physiology, researchers from the University's Institute of Integrative Biology attached fluorescent tags to carboxysomes and then used a fluorescence microscope to watch them in action within individual cells. By experimentally altering the amount of light available during cell growth the researchers observed how cyanobacteria regulate carbon fixation activity by changing the amount of carboxysomes in cells. The researchers also used chemical inhibitors that modify metabolism to monitor how this affects the distribution pattern of carboxysomes. They found that carboxysomes can either spread out or sit in the central line of the rod-shaped cell, depending on the redox states of electron transport pathways induced by the inhibitors. In collaboration with Dr Steve Barrett from the University's Department of Physics, the team developed a method to statistically analyse hundreds to thousands of bacterial cells from the microscope images. Co-author Dr Fang Huang, said: "It's exciting that through this technique we can now monitor, in real time, how bacteria modulate carboxysomes to maximise their carbon-fixing capacity. Our findings also provide some new clues about the relationship between the positioning of carboxysomes and cell metabolism." Carboxysomes are of interest to synthetic biologists and bioengineers, who hope to find ways to utilise their energy-boosting potential in food and biofuel production. Dr Luning Liu, lead author of the research, said: "Introducing cyanobacterial carboxysomes into plant chloroplasts could potentially improve the efficiency of photosynthesis and thereby the biomass yields. "There's still a lot we need to learn before their potential can be exploited. At this stage, we're just starting to understand how these fascinating cellular machines work, and this study marks another important step forward in this process." Explore further: Scientists discover how ocean bacterium turns carbon into fuel (w/ Video) More information: Light modulates the biosynthesis and organization of cyanobacterial carbon fixation machinery through photosynthetic electron flow. Plant Physiology, doi: dx.doi.org/10.1104/pp.16.00107

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