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1.
We study the evolution of the rate of self-fertilization in response to deleterious mutations at multiple loci. Although partial selfing induces associations among loci even in the absence of linkage, associations among mutations at different loci are of a smaller order of magnitude than the mutation rate. Genotypes that carry homozygous lethal mutations in heterozygous form at i loci occur in frequencies of the order (Ti) mu i, in which T denotes the number of viability loci and mu the mutation rate. While associations between mutations at different loci remain small even under inbreeding, each viability locus develops an association with the modifier of the rate of self-fertilization that substantially affects the evolution of the breeding system. Positive associations between enhancers of selfing and haplotypes carrying multiple wild-type alleles and positive associations in heterozygosity between the modifier locus and the viability loci promote evolutionary increases in the rate of self-fertilization. 相似文献
2.
WhileEscherichia coli is common as a commensal organism in the distal ileum and colon, the presence of colonization factors (CF) on pathogenic strains ofE. coli facilitates attachment of the organism to intestinal receptor molecules in a species- and tissue-specific fashion. After the initial adherence, colonization occurs, and the involvement of additional virulence determinants leads to illness. EnterotoxigenicE. coli (ETEC) is the most extensively studied of the five categories ofE. coli that cause diarrheal disease, and has the greatest impact on health worldwide. ETEC can be isolated from domestic animals and humans. The biochemistry, genetics, epidemiology, antigenic characteristics, and cell and receptor binding properties of ETEC have been extensively described. Another major category, enteropathogenicE. coli (EPEC), has virulence mechanisms, primarily effacement and cytoskeletal rearrangement of intestinal brush borders, that are distinct from ETEC. An EPEC CF receptor has been purified and characterized as a sialidated transmembrane glycoprotein complex directly attached to actin, thereby associating CF-binding with host-cell response. Three, additional categories ofE. coli diarrheal disease, their colonization factors and their host cell receptors are discussed. It appears that biofilms exist in the intestine in a manner similar to oral bacterial biofilms, and thatE. coli is part of these biofilms as both commensals and pathogens.Abbreviations CF
colonization factor
- CFA
Colonization Factor Antigen
- CS
coli-surface-associated antigen
- EAggEC
enteroaggregativeE. coli
- ECDD
E. coli diarrheal disease
- EHEC
enterohemorrhagicE. coli
- EIEC
enteroinvasiveE. coli
- EPEC
enteropathogenicE. coli
- ETEC
enterotoxigenicE. coli
- Gal
galactose
- GalNAc
N-acetyl galactosamine
- LT
heat-labile toxin
- NeuAc
N-acetyl neuraminic acid
- PCF
Putative colonization factor
- RBC
red blood cells
- SLT
Shiga-like toxin
- ST
heat-stable toxin 相似文献
3.
Nuclear and cytoplasmic determinants jointly influence the sex ratio in several organisms. A mathematical model of a maternally inherited extra-chromosomal agent that affects the fitness of its carriers and distorts the sex ratio in their broods is analyzed. The agent is transmitted through the cytoplasm from mother to daughter, or it may pass contagiously among females of the same generation. It is shown that under natural selection the deviation between the population sex ratio and Fisher's optimum value evolves to a minimum. 相似文献
4.
We examined gazelle peripheral blood leucocytes using the α-Naphthyl acetate esterase (ANAE) staining technique (pH 5.8). Our purpose was to determine the percentage of ANAE positive lymphocytes. The proportion of ANAE positive T-lymphocytes was 72%. T-lymphocytes showed an ANAE positive reaction, but eosinophilic granulocytes and monocytes also showed a positive reaction. By contrast, no reaction was detected in B-lymphocytes, neutrophil granulocytes or platelets. The reaction observed in T-lymphocytes was a red-brown coloration, usually 1–2 granules, but enough granules to fill the cytoplasm were detected rarely. As a result of ANAE enzyme staining, we concluded that the staining technique can be used as a cytochemical marker for gazelle T-lymphocytes. 相似文献
5.
6.
Marcy K. Uyenoyama 《Theoretical population biology》1979,15(1):58-85
A continuous, graded form of group selection which does not involve extinction of demes can effectively oppose selection on the individual level against an altruistic allele under fluctuating environments in infinitely large demes among which uniform mixing occurs every generation. Although group selection cannot alter the conditions necessary for the initial increase of altruistic alleles, group selection can significantly influence the stationary distribution of gene frequency which is attained once stochastic forces have allowed theirintroduction. Drift is a more effective source of variation than fluctuations in selection when the variance in selection is moderate to small. High numbers of demes promote polymorphism under both graded group selection and extinction group selection. 相似文献
7.
Yu‐Chiang Lai Chandana Kondapalli Ronny Lehneck James B Procter Brian D Dill Helen I Woodroof Robert Gourlay Mark Peggie Thomas J Macartney Olga Corti Jean‐Christophe Corvol David G Campbell Aymelt Itzen Matthias Trost Miratul MK Muqit 《The EMBO journal》2015,34(22):2840-2861
Mutations in the PTEN‐induced kinase 1 (PINK1) are causative of autosomal recessive Parkinson''s disease (PD). We have previously reported that PINK1 is activated by mitochondrial depolarisation and phosphorylates serine 65 (Ser65) of the ubiquitin ligase Parkin and ubiquitin to stimulate Parkin E3 ligase activity. Here, we have employed quantitative phosphoproteomics to search for novel PINK1‐dependent phosphorylation targets in HEK (human embryonic kidney) 293 cells stimulated by mitochondrial depolarisation. This led to the identification of 14,213 phosphosites from 4,499 gene products. Whilst most phosphosites were unaffected, we strikingly observed three members of a sub‐family of Rab GTPases namely Rab8A, 8B and 13 that are all phosphorylated at the highly conserved residue of serine 111 (Ser111) in response to PINK1 activation. Using phospho‐specific antibodies raised against Ser111 of each of the Rabs, we demonstrate that Rab Ser111 phosphorylation occurs specifically in response to PINK1 activation and is abolished in HeLa PINK1 knockout cells and mutant PINK1 PD patient‐derived fibroblasts stimulated by mitochondrial depolarisation. We provide evidence that Rab8A GTPase Ser111 phosphorylation is not directly regulated by PINK1 in vitro and demonstrate in cells the time course of Ser111 phosphorylation of Rab8A, 8B and 13 is markedly delayed compared to phosphorylation of Parkin at Ser65. We further show mechanistically that phosphorylation at Ser111 significantly impairs Rab8A activation by its cognate guanine nucleotide exchange factor (GEF), Rabin8 (by using the Ser111Glu phosphorylation mimic). These findings provide the first evidence that PINK1 is able to regulate the phosphorylation of Rab GTPases and indicate that monitoring phosphorylation of Rab8A/8B/13 at Ser111 may represent novel biomarkers of PINK1 activity in vivo. Our findings also suggest that disruption of Rab GTPase‐mediated signalling may represent a major mechanism in the neurodegenerative cascade of Parkinson''s disease. 相似文献
8.
Marcy K. Uyenoyama 《Evolution; international journal of organic evolution》1986,40(2):388-404
The effect of biparental inbreeding on the conditions governing the evolution of selfing is examined using recursions in mating-type frequencies. Sibmating in combination with random outcrossing influences two key determinants of the adaptive value of selfing: 1) the meiotic cost of biparental reproduction and 2) the level of inbreeding depression due to deleterious mutations. Biparental inbreeding serves to maintain biparental reproduction by increasing relatedness between parents and their biparentally derived offspring and introduces the possibility of an optimal mating system that incorporates both modes of reproduction. Biparental inbreeding serves to promote uniparental reproduction by reducing the relative inbreeding depression suffered by uniparental offspring. The net effect of these two antagonistic trends depends upon the extent to which mutational load accounts for differences in the numbers of the two types of offspring. A brief summary of the empirical literature suggests that: 1) biparental inbreeding may occur in populations exhibiting mixed mating systems; 2) while inbreeding depression represents an important factor, it does not account entirely for differences in offspring number between the two modes of reproduction. 相似文献
9.
The evolutionary dynamics of self-incompatibility systems 总被引:1,自引:0,他引:1
Self-incompatible flowering plants reject pollen that expresses the same mating specificity as the pistil (female reproductive tract). In most plant families, pollen and pistil mating specificities segregate as a single locus, the S locus. In at least two self-incompatibility systems, distinct pollen and pistil specificity genes are embedded in an extensive nonrecombining tract. To facilitate consideration of how new S locus specificities arise in systems with distinct pollen and pistil genes, we present a graphical model for the generation of hypotheses. It incorporates the evolutionary principle that nonreciprocal siring success (cross-pollinations between two plants produce seeds in only one direction) tends to favor the rejecting partner. This model suggests that selection within S-allele specificity classes could accelerate the rate of nonsynonymous (amino acid-changing) substitutions, with periodic selective sweeps removing segregating variation within classes. Accelerated substitution within specificity classes could also promote the origin of new S-allele specificities. 相似文献
10.
AB Chang NC Cox J Purcell JM Marchant PJ Lewindon GJ Cleghorn LC Ee GD Withers MK Patrick J Faoagali 《Respiratory research》2005,6(1):1-5