98 research outputs found
Disentangling the Benefits of Sex
In experiments with a facultatively sexual rotifer, populations adapting to novel environments evolve higher rates of sex because sexual mixing quickly assembles well-adapted genotypes
Red Queen Coevolution on Fitness Landscapes
Species do not merely evolve, they also coevolve with other organisms.
Coevolution is a major force driving interacting species to continuously evolve
ex- ploring their fitness landscapes. Coevolution involves the coupling of
species fit- ness landscapes, linking species genetic changes with their
inter-specific ecological interactions. Here we first introduce the Red Queen
hypothesis of evolution com- menting on some theoretical aspects and empirical
evidences. As an introduction to the fitness landscape concept, we review key
issues on evolution on simple and rugged fitness landscapes. Then we present
key modeling examples of coevolution on different fitness landscapes at
different scales, from RNA viruses to complex ecosystems and macroevolution.Comment: 40 pages, 12 figures. To appear in "Recent Advances in the Theory and
Application of Fitness Landscapes" (H. Richter and A. Engelbrecht, eds.).
Springer Series in Emergence, Complexity, and Computation, 201
The relationship between patient physiology and cancer-specific survival following curative resection of colorectal cancer
The impact of patient physiology on cancer-specific survival is poorly documented. Patient physiology predicted overall, cancer-specific (Physiology Score>30; HR 8.64 (95% CI 3.00–24.92); P=0.0005) and recurrence-free survival (Physiology Score >30; HR 7.44 (95% CI 1.99–27.73); P=0.003) independent of Dukes stage following potentially curative surgery for colorectal cancer. This independent negative association with survival is a novel observation
Improving the hyperpolarization of (31)p nuclei by synthetic design
Traditional (31)P NMR or MRI measurements suffer from low sensitivity relative to (1)H detection and consequently require longer scan times. We show here that hyperpolarization of (31)P nuclei through reversible interactions with parahydrogen can deliver substantial signal enhancements in a range of regioisomeric phosphonate esters containing a heteroaromatic motif which were synthesized in order to identify the optimum molecular scaffold for polarization transfer. A 3588-fold (31)P signal enhancement (2.34% polarization) was returned for a partially deuterated pyridyl substituted phosphonate ester. This hyperpolarization level is sufficient to allow single scan (31)P MR images of a phantom to be recorded at a 9.4 T observation field in seconds that have signal-to-noise ratios of up to 94.4 when the analyte concentration is 10 mM. In contrast, a 12 h 2048 scan measurement under standard conditions yields a signal-to-noise ratio of just 11.4. (31)P-hyperpolarized images are also reported from a 7 T preclinical scanner
Rapid evolution of microbe-mediated protection against pathogens in a worm host.
Microbes can defend their host against virulent infections, but direct evidence for the adaptive origin of microbe-mediated protection is lacking. Using experimental evolution of a novel, tripartite interaction, we demonstrate that mildly pathogenic bacteria (Enterococcus faecalis) living in worms (Caenorhabditis elegans) rapidly evolved to defend their animal hosts against infection by a more virulent pathogen (Staphylococcus aureus), crossing the parasitism-mutualism continuum. Host protection evolved in all six, independently selected populations in response to within-host bacterial interactions and without direct selection for host health. Microbe-mediated protection was also effective against a broad spectrum of pathogenic S. aureus isolates. Genomic analysis implied that the mechanistic basis for E. faecalis-mediated protection was through increased production of antimicrobial superoxide, which was confirmed by biochemical assays. Our results indicate that microbes living within a host may make the evolutionary transition to mutualism in response to pathogen attack, and that microbiome evolution warrants consideration as a driver of infection outcome
Inverted Expression Profiles of Sex-Biased Genes in Response to Toxicant Perturbations and Diseases
10.1371/journal.pone.0056668PLoS ONE82
Hv-CBF2A overexpression in barley accelerates COR gene transcript accumulation and acquisition of freezing tolerance during cold acclimation
Abstract C-Repeat Binding Factors (CBFs) are DNAbinding
transcriptional activators of gene pathways imparting
freezing tolerance. Poaceae contain three CBF subfamilies,
two of which, HvCBF3/CBFIII and HvCBF4/CBFIV,
are unique to this taxon. To gain mechanistic insight into
HvCBF4/CBFIV CBFs we overexpressed Hv-CBF2A in
spring barley (Hordeum vulgare) cultivar ‘Golden Promise’.
The Hv-CBF2A overexpressing lines exhibited stunted
growth, poor yield, and greater freezing tolerance compared
to non-transformed ‘Golden Promise’. Differences in
freezing tolerance were apparent only upon cold acclimation.
During cold acclimation freezing tolerance of the
Hv-CBF2A overexpressing lines increased more rapidly
than that of ‘Golden Promise’ and paralleled the freezing
tolerance of the winter hardy barley ‘Dicktoo’. Transcript
levels of candidate CBF target genes, COR14B and DHN5
were increased in the overexpressor lines at warm temperatures,
and at cold temperatures they accumulated to much
higher levels in the Hv-CBF2A overexpressors than in
‘Golden Promise’. Hv-CBF2A overexpression also
increased transcript levels of other CBF genes at FROST
RESISTANCE-H2-H2 (FR-H2) possessing CRT/DRE sites
in their upstream regions, the most notable of which was
CBF12. CBF12 transcript levels exhibited a relatively constant
incremental increase above levels in ‘Golden Promise’
both at warm and cold. These data indicate that Hv-CBF2A
activates target genes at warm temperatures and that transcript
accumulation for some of these targets is greatly
enhanced by cold temperatures
Coexisting Cyclic Parthenogens Comprise a Holocene Species Flock in Eubosmina
Background: Mixed breeding systems with extended clonal phases and weak sexual recruitment are widespread in nature but often thought to impede the formation of discrete evolutionary clusters. Thus, cyclic parthenogens, such as cladocerans and rotifers, could be predisposed to ‘‘species problems’ ’ and a lack of discrete species. However, species flocks have been proposed for one cladoceran group, Eubosmina, where putative species are sympatric, and there is a detailed paleolimnological record indicating a Holocene age. These factors make the Eubosmina system suitable for testing the hypotheses that extended clonal phases and weak sexual recruitment inhibit speciation. Although common garden experiments have revealed a genetic component to the morphotypic variation, the evolutionary significance of the morphotypes remains controversial. Methodology/Principal Findings: In the present study, we tested the hypothesis of a single polymorphic species (i.e., mixing occurs but selection maintains genes for morphology) in four northern European lakes where the morphotypes coexist. Our evidence is based on nuclear DNA sequence, mitochondrial DNA sequence, and morphometric analysis of coexisting morphotypes. We found significant genetic differentiation, genealogical exclusivity, and morphometric differentiation for coexisting morphotypes. Conclusions: We conclude that the studied morphotypes represent a group of young species undergoing speciation wit
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