scholarly journals Mutational robustness changes during long-term adaptation in laboratory budding yeast populations

2021 ◽  
Author(s):  
Milo Johnson ◽  
Michael M. Desai
Keyword(s):  
Gene Disruption ◽  
Fitness Landscape ◽  
Single Step ◽  
The Other ◽  
Specific Gene ◽  
Deleterious Mutations ◽  
Mutational Robustness ◽  
Fitness Effects ◽  
The Mean

As an adapting population traverses the fitness landscape, its local neighborhood (i.e., the collection of fitness effects of single-step mutations) can change shape because of interactions with mutations acquired during evolution. These changes to the distribution of fitness effects can affect both the rate of adaptation and the accumulation of deleterious mutations. However, while numerous models of fitness landscapes have been proposed in the literature, empirical data on how this distribution changes during evolution remains limited. In this study, we directly measure how the fitness landscape neighborhood changes during laboratory adaptation. Using a barcode-based mutagenesis system, we measure the fitness effects of 91 specific gene disruption mutations in genetic backgrounds spanning 8,000-10,000 generations of evolution in two constant environments. We find that the mean of the distribution of fitness effects decreases in one environment, indicating a reduction in mutational robustness, but does not change in the other. We show that these distribution-level patterns result from biases in variable patterns of epistasis at the level of individual mutations, including fitness-correlated and idiosyncratic epistasis.

scholarly journals Higher-fitness yeast genotypes are less robust to deleterious mutations

Science ◽  
2019 ◽  
Vol 366 (6464) ◽  
pp. 490-493 ◽  
Author(s):  
Milo S. Johnson ◽  
Alena Martsul ◽  
Sergey Kryazhimskiy ◽  
Michael M. Desai
Keyword(s):  
Second Order ◽  
Order Selection ◽  
Deleterious Mutations ◽  
Mutational Robustness ◽  
First Order ◽  
Fitness Effects ◽  
Yeast Strains ◽  
Selection For ◽  
Microbial Systems ◽  
Insertion Mutations

Natural selection drives populations toward higher fitness, but second-order selection for adaptability and mutational robustness can also influence evolution. In many microbial systems, diminishing-returns epistasis contributes to a tendency for more-fit genotypes to be less adaptable, but no analogous patterns for robustness are known. To understand how robustness varies across genotypes, we measure the fitness effects of hundreds of individual insertion mutations in a panel of yeast strains. We find that more-fit strains are less robust: They have distributions of fitness effects with lower mean and higher variance. These differences arise because many mutations have more strongly deleterious effects in faster-growing strains. This negative correlation between fitness and robustness implies that second-order selection for robustness will tend to conflict with first-order selection for fitness.

Isoelastic Cementless Total Hip Replacement in Rheumatoid Arthritis. Long-Term Results

1992 ◽  
Vol 2 (2) ◽  
pp. 43-46
Author(s):  
U. Fusco ◽  
R. Capelli ◽  
A. Avai ◽  
M. Gerundini ◽  
L. Colombini ◽  
...  
Keyword(s):  
Rheumatoid Arthritis ◽  
Hip Replacement ◽  
The Other ◽  
Long Term Results ◽  
X Rays ◽  
X Ray ◽  
The Mean ◽  
Cementless Total Hip Replacement

Between 1980 and 1987 we have implanted 46 isoelastic cementless THR in 40 patients affected with rheumatoid arthritis. We have reviewed 38 hips clinically and by X-ray. The mean follow-up was 8,5 years. Harris hip scores ranged from 30.6 preoperatively to 73,4 post-operatively when reviewed. While on the other hand Merle D'Aubigné hip scores ranged from 7,06 pre-operatively to 15,59 post-operatively. All patients have been satisfied, and X-rays showed an improvement for both Charnely and Gruen X-ray score.

OBSERVATIONS ON SUCCESSIVE PRO-OESTROUS LH SURGES IN INDIVIDUAL 4-DAY CYCLING AND POST-PSEUDOPREGNANT RATS

1978 ◽  
Vol 88 (2) ◽  
pp. 274-284 ◽  
Author(s):  
Alberto J. Carrillo ◽  
Charles H. Sawyer
Keyword(s):  
Mechanical Stimulation ◽  
Term Effect ◽  
Oestrous Cycle ◽  
The Other ◽  
Peak Amplitude ◽  
Lh Surge ◽  
Long Term Effect ◽  
The Mean ◽  
Stimulation Of

ABSTRACT The internal variations (i. e. in timing, duration and amplitude) of the LH surge mechanism within individual rats were examined by monitoring from 3 to 7 successive pro-oestrous LH surges in each of 5 regular 4-day cycling rats fitted with chronic intravenous cannulas. On each successive pro-oestrus blood was collected (0.5–0.6 ml hourly from 14.00–21.00) for radioimmunoassay of LH. The surgery of cannulation had no long-term effect on the regularity of the oestrous cycle. Two rats did, however, show briefly irregular cycles, including one with a 9-day period of anoestrus (pseudopregnancy). In three of the five rats successive pro-oestrous plasma LH curves (4 in one and 3 each in the other two) were internally very consistent in timing, shape and amplitude, However, between each 2 of these 3 animals there were distinct differences in the LH secretory patterns, by as much as 2 h in timing of the onset of the surge and its peak amplitude. The first two surges of the other two rats were atypical of their subsequent surges, which were mostly consistent in timing and amplitude. The pro-oestrous LH surge following the 9-day period of anoestrus was advanced by 2 h and elevated to twice the mean peak amplitude of the cyclic LH surges in that rat. Subsequently, post-PSP surges were studied in rats made pseudopregnant by mechanical stimulation of the cervix. In all cases the immediate post-PSP surge occurred earlier in the afternoon and with a greater peak amplitude than the subsequent cyclic LH surge in the same rat.

Longevity ofEchinostoma caproniin Balb/c mice

2008 ◽  
Vol 82 (1) ◽  
pp. 95-96 ◽  
Author(s):  
B. Fried ◽  
R.C. Peoples
Keyword(s):  
The Other ◽  
Term Survival ◽  
Long Term Survival ◽  
Echinostoma Caproni ◽  
Host Parasite Relationship ◽  
Parasite Relationship ◽  
The Mean ◽  
Host Parasite ◽  
Relationship Of

AbstractThis study used Balb/c mice to examine the longevity ofEchinostoma caproni. Five mice each exposed to 75 encysted metacercariae (cysts) were necropsied at 23 weeks postinfection (PI) (160 days PI). Two of the 5 were infected with a total of 33 worms; 23 in one mouse and 10 in the other. Body and organ area measurements showed that these worms were robust and normal in appearance. No signs of atrophy of any of the genital structures were observed. The mean ± SE of eggs/uterus per worm (n = 10) was 243 ± 6. This strain of mouse will be suitable to study the effect of long-term survival on the host–parasite relationship ofE. caproniin Balb/c mice.

scholarly journals Higher fitness yeast genotypes are less robust to deleterious mutations

2019 ◽  
Author(s):  
Milo S. Johnson ◽  
Alena Martsul ◽  
Sergey Kryazhimskiy ◽  
Michael M. Desai
Keyword(s):  
Second Order ◽  
Order Selection ◽  
Deleterious Mutations ◽  
Mutational Robustness ◽  
First Order ◽  
Fitness Effects ◽  
Yeast Strains ◽  
Selection For ◽  
Microbial Systems ◽  
Insertion Mutations

AbstractNatural selection drives populations towards higher fitness, but second-order selection for adaptability and mutational robustness can also influence the dynamics of adaptation. In many microbial systems, diminishing returns epistasis contributes to a tendency for more-fit genotypes to be less adaptable, but no analogous patterns for robustness are known. To understand how robustness varies across genotypes, we measure the fitness effects of hundreds of individual insertion mutations in a panel of yeast strains. We find that more-fit strains are less robust: they have distributions of fitness effects (DFEs) with lower mean and higher variance. These shifts in the DFE arise because many mutations have more strongly deleterious effects in faster-growing strains. This negative correlation between fitness and robustness implies that second-order selection for robustness will tend to conflict with first-order selection for fitness.

scholarly journals Paralog dependency indirectly affects the robustness of human cells

2019 ◽  
Author(s):  
Rohan Dandage ◽  
Christian R Landry
Keyword(s):  
Gene Loss ◽  
Fitness Landscape ◽  
Human Cells ◽  
The Other ◽  
Gene Copy ◽  
Deleterious Mutations ◽  
Loss Of Function ◽  
Protein Protein Interaction ◽  
Interaction Partners ◽  
Paralogous Proteins

SummaryGene duplicates provide protection against loss-of-function mutations. This protective redundancy partly relies on the fact that paralogs carry their functions independently, i.e. the inactivation of one gene copy does not impair the function of the other copy. However, a significant fraction of paralogous proteins may form functionally dependent pairs, for instance through heteromerization. As a consequence, one could expect these heteromeric paralogs to be less protective against deleterious mutations. To test this hypothesis, we examined the fitness landscape of gene loss-of-function by CRISPR-Cas9 in more than 450 human cell lines. Our analysis revealed a robustness landscape of human cells showing regions of higher vulnerability to gene inactivation as a function of key paralog properties. We find that heteromerizing paralogs are indeed less protective than non-heteromeric ones, but this association is largely due to their higher abundance and their larger number of protein-protein interaction partners.

scholarly journals Diverse phenotypic and genetic responses to short-term selection in evolving Escherichia coli populations

2015 ◽  
Author(s):  
Marcus M Dillon ◽  
Nicholas P Rouillard ◽  
Brian Van Dam ◽  
Romain Gallet ◽  
Vaughn S Cooper
Keyword(s):  
Escherichia Coli ◽  
Fitness Landscape ◽  
Single Point ◽  
Beneficial Mutations ◽  
True Nature ◽  
Term Selection ◽  
Adaptive Mutations ◽  
Fitness Effects ◽  
Genetic Responses

Beneficial mutations fuel adaptation by altering phenotypes that enhance the fit of organisms to their environment. However, the phenotypic effects of mutations often depend on ecological context, making the distribution of effects across multiple environments essential to understanding the true nature of beneficial mutations. Studies that address both the genetic basis and ecological consequences of adaptive mutations remain rare. Here, we characterize the direct and pleiotropic fitness effects of a collection of 21 first-step beneficial mutants derived from naive and adapted genotypes used in a long-term experimental evolution of Escherichia coli. Whole-genome sequencing was used to identify most beneficial mutations. In contrast to previous studies, we find diverse fitness effects of mutations selected in a simple environment and few cases of genetic parallelism. The pleiotropic effects of these mutations were predominantly positive but some mutants were highly antagonistic in alternative environments. Further, the fitness effects of mutations derived from the adapted genotypes were dramatically reduced in nearly all environments. These findings suggest that many beneficial variants are accessible from a single point on the fitness landscape, and the fixation of alternative beneficial mutations may have dramatic consequences for niche breadth reduction via metabolic erosion.

Long-term population dynamics of Aphelenchoides besseyi on Oryza sativa in a paddy field, and changes in the pathological and ecological traits of the two populations

Nematology ◽  
2021 ◽  
pp. 1-17
Author(s):  
Shigeru Hoshino ◽  
Katsumi Togashi
Keyword(s):  
Population Dynamics ◽  
Oryza Sativa ◽  
The Other ◽  
Ecological Traits ◽  
Reproduction Curve ◽  
Aphelenchoides Besseyi ◽  
The Mean ◽  
Two Peaks ◽  
Two Populations

Summary An Oryza sativa cultivar inoculated with the white tip nematode, Aphelenchoides besseyi, was cultivated over 18 years to investigate the population dynamics of the nematode and the change in the virulence of nematodes and tolerance/resistance of plants. The mean number of living nematodes per seed (S) showed two peaks, each of which was followed by a 3-year decrease in the S value, during the initial 10 years. The annual reproduction curve between in year and in year t had a peak in a range of of <1.1. The incidence of white tip disease increased with increasing mean number of living nematodes seed−1 in the previous year, whereas the proportion of seeds with living nematodes increased with increasing mean number of living nematodes seed−1 in the current year. Inoculation tests of the nematode cohorts on the seedling cohorts derived from seeds harvested in the same or different years indicated that the initial 6-year interaction between the rice and nematode populations caused the nematodes to increase the incidence of white tip disease and to decrease the degree of seed swelling and the proportion of heavy seeds. On the other hand, the interaction caused the rice plants to prevent the incidence of disease from increasing and the degree of seed swelling and the proportion of heavy seeds from decreasing.

scholarly journals ON SOME GRAVITOMAGNETIC SPIN–SPIN EFFECTS FOR ASTRONOMICAL BODIES

2003 ◽  
Vol 12 (01) ◽  
pp. 35-43 ◽  
Author(s):  
LORENZO IORIO
Keyword(s):  
Angular Momentum ◽  
The Other ◽  
Spin Interaction ◽  
Spinning Particle ◽  
Spin Effects ◽  
Gravitomagnetic Field ◽  
The Mean ◽  
Moving Particle ◽  
Proper Angular Momentum

In this paper we look at the gravitational spin–spin interaction between macroscopic astronomical bodies. In particular, we calculate their post-Newtonian orbital effects of order [Formula: see text] on the trajectory of a spinning particle with proper angular momentum s moving in the external gravitomagnetic field generated by a central spinning mass with proper angular momentum J. It turns out that, at order [Formula: see text] in the orbiter's eccentricity, the eccentricity the pericenter and the mean anomaly rates of the moving particle are affected by long-term harmonic effects. If, on one hand, they are undetectable in the Solar System, on the other, maybe in an astrophysical context like that of the binary millisecond pulsars there will be some hopes of measuring them in the future, provided that substantial improvements in the accuracy of the detection of the periastron rate will occur.

Population fluctuations in spruce grouse: what determines their numbers in spring?

1987 ◽  
Vol 65 (10) ◽  
pp. 2430-2435 ◽  
Author(s):  
D. A. Boag ◽  
M. A. Schroeder
Keyword(s):  
Population Size ◽  
Breeding Success ◽  
The Other ◽  
Population Fluctuations ◽  
Spacing Behaviour ◽  
Term Change ◽  
The Status ◽  
The Mean ◽  
One Year

The number of spruce grouse (Falcipennis (Canachites) franklinii) present in the spring population on a 247-ha block of pine-dominated habitat in southwestern Alberta was counted annually over a 21-year period. During the first 5 years of this study, the population increased steadily from 7.3 to 16.6 grouse/100 ha. Subsequently, for a period of 11 years, numbers were relatively stable at higher densities (19.0–29.1 grouse/100 ha). During the last 5-year period, the population declined to levels lower than at the onset of the study (16.6–4.9 grouse/100 ha). Year to year fluctuations in the size of this population were considered in the light of two hypotheses put forward to explain such fluctuations (spacing behaviour and breeding success). We concluded that both hypotheses were needed to explain our observations. During those years when spring population size fell below the mean number of grouse recorded over the 21-year period (17.8/100 ha), there was some evidence that breeding success in one year may have influenced population size the following spring but we found no evidence that spacing behaviour was important in limiting numbers under these conditions. On the other hand, when the size of the spring population was greater than the mean there was no evidence that breeding success influenced changes in population size the following spring, but there was evidence that spacing behaviour was limiting recruitment. The long-term change in population size appeared to be tied to the status of the fire sere inhabited: maturation of the forest (principally an increase in the height) was accompanied by a decline in population size.

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