抗原变异可使得多种致病微生物易于逃避宿主免疫应答。表达在感染红细胞表面的恶性疟原虫红细胞表面蛋白1（PfPMP1）与感染红细胞、内皮细胞、树突状细胞以及胎盘的单个或多个受体作用，在黏附及免疫逃避中起关键的作用。每个单倍体基因组var基因家族编码约60种成员，通过启动转录不同的var基因变异体为抗原变异提供了分子基础。

疟原虫var基因转换速率变化导致抗原变异[英]／Paul H, Robert P, Christodoulou Z, et al//Proc Natl Acad Sci U S A

genalex is a user-friendly cross-platform package that runs within Microsoft Excel, enabling population genetic analyses of codominant, haploid and binary data. Allele frequency-based analyses include heterozygosity, F statistics, Nei's genetic distance, population assignment, probabilities of identity and pairwise relatedness. Distance-based calculations include amova, principal coordinates analysis (PCA), Mantel tests, multivariate and 2D spatial autocorrelation and twogener. More than 20 different graphs summarize data and aid exploration. Sequence and genotype data can be imported from automated sequencers, and exported to other software. Initially designed as tool for teaching, genalex 6 now offers features for researchers as well. Documentation and the program are available at http://www.anu.edu.au/BoZo/GenAlEx/

genalex 6: genetic analysis in Excel. Population genetic software for teaching and research

Preface to the Princeton Landmarks in Biology Edition vii Preface xi Symbols Used xiii 1. The Importance of Islands 3 2. Area and Number of Speicies 8 3. Further Explanations of the Area-Diversity Pattern 19 4. The Strategy of Colonization 68 5. Invasibility and the Variable Niche 94 6. Stepping Stones and Biotic Exchange 123 7. Evolutionary Changes Following Colonization 145 8. Prospect 181 Glossary 185 References 193 Index 201

The Theory of Island Biogeography

We present here a framework for the study of molecular variation within a single species. Information on DNA haplotype divergence is incorporated into an analysis of variance format, derived from a matrix of squared-distances among all pairs of haplotypes. This analysis of molecular variance (AMOVA) produces estimates of variance components and F-statistic analogs, designated here as phi-statistics, reflecting the correlation of haplotypic diversity at different levels of hierarchical subdivision. The method is flexible enough to accommodate several alternative input matrices, corresponding to different types of molecular data, as well as different types of evolutionary assumptions, without modifying the basic structure of the analysis. The significance of the variance components and phi-statistics is tested using a permutational approach, eliminating the normality assumption that is conventional for analysis of variance but inappropriate for molecular data. Application of AMOVA to human mitochondrial DNA haplotype data shows that population subdivisions are better resolved when some measure of molecular differences among haplotypes is introduced into the analysis. At the intraspecific level, however, the additional information provided by knowing the exact phylogenetic relations among haplotypes or by a nonlinear translation of restriction-site change into nucleotide diversity does not significantly modify the inferred population genetic structure. Monte Carlo studies show that site sampling does not fundamentally affect the significance of the molecular variance components. The AMOVA treatment is easily extended in several different directions and it constitutes a coherent and flexible framework for the statistical analysis of molecular data.

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Analysis of molecular variance inferred from metric distances among DNA haplotypes: application to human mitochondrial DNA restriction data.

A majority of cellular proteins function as part of multimeric complexes of two or more subunits. Multimer formation requires interactions between protein surfaces that lead to closed structures, such as dimers and tetramers. If proteins interact in an open-ended way, uncontrolled growth of fibrils can occur, which is likely to be detrimental in most cases. We present a statistical physics model that allows aggregation of proteins as either closed dimers or open fibrils of all lengths. We use pairwise amino-acid contact energies to calculate the energies of interacting protein surfaces. The probabilities of all possible aggregate configurations can be calculated for any given sequence of surface amino acids. We link the statistical physics model to a population genetics model that describes the evolution of the surface residues. When proteins evolve neutrally, without selection for or against multimer formation, we find that a majority of proteins remain as monomers at moderate concentrations, but strong dimer-forming or fibril-forming sequences are also possible. If selection is applied in favor of dimers or in favor of fibrils, then it is easy to select either dimer-forming or fibril-forming sequences. It is also possible to select for oriented fibrils with protein subunits all aligned in the same direction. We measure the propensities of amino acids to occur at interfaces relative to noninteracting surfaces and show that the propensities in our model are strongly correlated with those that have been measured in real protein structures. We also show that there are significant differences between amino acid frequencies at isologous and heterologous interfaces in our model, and we observe that similar effects occur in real protein structures.

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Evolution of protein interfaces in multimers and fibrils.

Abstract Metal nanoparticles, especially silver, have been used in various medical scenarios, due to their excellent antimicrobial effects. Recent studies have shown that AgNPs do not exert mutagenic effects on target bacteria, but the degree to which they compromise eukaryotic genomes remains unclear. To study this, we evaluated the mutagenic effects of AgNPs on the fission yeast Schizosaccharomyces pombe ATCC-16979, of which ∼23% genes are homologous to human ones, at single-nucleotide resolution, and whole-genome scale by running 283 mutation accumulation lines for ∼260,000 cell divisions in total. We also explored the action and mutagenesis mechanisms using differential gene-expression analysis based on RNAseq. Upon AgNPs treatment, the genomic base-substitution mutation rate of S. pombe at four-fold degenerate sites increased by 3.46×, and small indels were prone to occur in genomic regions that are not simple sequence repeats. The G:C → T:A transversion rate was also significantly increased, likely mostly from oxidative damage. Thus, in addition to their antimicrobial potency, AgNPs might pose slight genotoxicity threats to eukaryotic and possibly human genomes, though at a low magnitude.

/pdf/silver-nanoparticles-elevate-mutagenesis-of-eukaryotic-11a6p6xi.pdf

Silver nanoparticles elevate mutagenesis of eukaryotic genomes

High-throughput sequencing of amplicons has been widely used to precisely and efficiently identify species compositions and analyze community structures, greatly promoting biological studies involving large amounts of complex samples, especially those involving environmental and pathogen-monitoring ones. However, commercial library preparation kits for amplicon sequencing, which generally require multiple steps, including adapter ligation and indexing, are expensive and time-consuming, especially for applications at a large scale. Here, to overcome this technical hurdle, we present a one-step PCR amplicon library construction (OSPALC) protocol for amplicon library preparations in the lab along with a QIIME2-based amplicon analysis pipeline. High-quality reads have been generated by this approach to reliably identify species compositions of mock bacterial communities and environmental samples. With this protocol, the amplicon library construction is completed through one regular PCR with long primers, and the total cost per DNA/cDNA sample decreases to just 1/15 of the typical cost via service providers. Empirically tested primers to construct OSPALC libraries for 16S rDNA V4 regions are demonstrated as a case study. Criteria to design primers targeting at any regions of prokaryotic and eukaryotic genomes are also suggested. In principle, OSPALC can be conveniently used in amplicon library constructions of any target gene of both prokaryotes and eukaryotes at the DNA or RNA levels, and will facilitate research in numerous fields.

/pdf/one-step-pcr-amplicon-library-construction-ospalc-version-1-35fnotxk.pdf

One-Step PCR Amplicon Library Construction (OSPALC, version 1)

Cell lysis, a process that releases host oligonucleotides, is required in many biotechnological applications. However, intact oligonucleotides in crude cellular lysates increase the viscosity of lysates, which complicates downstream processes and routine laboratory workflows. To address this, nucleases that hydrolyze the intact oligonucleotides are commonly added, either as purified enzymes or co-expressed in genetically engineered bacterial strains. To measure oligonucleotide hydrolysis, common DNA quantification methods, such as qPCR or fluorescence-based, require expensive reagents and equipment, and cannot distinguish different-sized DNA fragments. Here, we outline a simple alternative method for measuring DNA/RNA hydrolysis in cellular lysates, by measuring their viscosity. This method only requires common laboratory supplies and a cell phone camera.

Measuring Oligonucleotide Hydrolysis in Cellular Lysates via Viscosity Measurements.

Studies of closely related species with known ecological differences provide exceptional opportunities for understanding the genetic mechanisms of evolution. Here, we compared population-genomics data between D. pulex and D. pulicaria, two reproductively compatible sister species experiencing ecological speciation, the first largely confined to intermittent ponds and the second to permanent lakes in the same geographic region. D. pulicaria has lower genome-wide nucleotide diversity, a smaller effective population size, higher incidence of private alleles, and substantially more linkage-disequilibrium than D. pulex. Functional enrichment analysis revealed that positively selected genes in D. pulicaria are enriched in potentially aging-related categories such as cellular homeostasis, which may explain the extended lifespan in D. pulicaria. We also found that opsin-related genes, which may mediate photoperiodic responses, are under different selection pressures in these two species. Additionally, genes involved in mitochondrial functions, ribosomes, and responses to environmental stimuli are found to be under positive selection in both species. Our results provide insights into the physiological traits that differ within this regionally sympatric sister-species pair that occupies unique microhabitats.

/pdf/evolutionary-genomics-of-sister-species-differing-in-qx8o0xpv.pdf

Michael Lynch

Papers

Evolution of protein interfaces in multimers and fibrils.

Silver nanoparticles elevate mutagenesis of eukaryotic genomes

One-Step PCR Amplicon Library Construction (OSPALC, version 1)

Measuring Oligonucleotide Hydrolysis in Cellular Lysates via Viscosity Measurements.

Evolutionary Genomics of Sister Species Differing in Effective Population Sizes and Recombination Rates