The Reproducibility of an Inferred Tree and the Diploidization of Gene Segregation after Genome Duplication.

We previously introduced a numerical quantity called the stability (Ps) of an inferred tree and showed that for the tree to be reliable this stability as well as the reliability of the tree, which is usually computed as the bootstrap probability (Pb), must be high. However, if genome duplication occurs in a species, a gene family of the genome also duplicates, and for this reason alone some Ps values can be high in a tree of the duplicated gene families. In addition, the topology of the duplicated gene family can be similar to that of the original gene family if such gene families are identifiable.

The Reliability and Stability of an Inferred Phylogenetic Tree from Empirical Data.

The reliability of a phylogenetic tree obtained from empirical data is usually measured by the bootstrap probability (Pb) of interior branches of the tree. If the bootstrap probability is high for most branches, the tree is considered to be reliable. If some interior branches show relatively low bootstrap probabilities, we are not sure that the inferred tree is really reliable.

Efficiencies of the NJp, Maximum Likelihood, and Bayesian Methods of Phylogenetic Construction for Compositional and Noncompositional Genes.

At the present time it is often stated that the maximum likelihood or the Bayesian method of phylogenetic construction is more accurate than the neighbor joining (NJ) method. Our computer simulations, however, have shown that the converse is true if we use p distance in the NJ procedure and the criterion of obtaining the true tree (Pc expressed as a percentage) or the combined quantity (c) of a value of Pc and a value of Robinson-Foulds' average topological error index (dT). This c is given by Pc (1 - dT/dTmax) = Pc (m - 3 - dT/2)/(m - 3), where m is the number of taxa used and dTmax is the maximum possible value of dT, which is given by 2(m - 3).

POPTREEW: web version of POPTREE for constructing population trees from allele frequency data and computing some other quantities.

POPTREE software, including the command line (POPTREE) and the Windows (POPTREE2) versions, is available to perform evolutionary analyses of allele frequency data, computing distance measures for constructing population trees and average heterozygosity (H) (measure of genetic diversity within populations) and G(ST) (measure of genetic differentiation among subdivided populations). We have now developed a web version POPTREEW (http://www.med.

Evolution of the sex-lethal gene in insects and origin of the sex-determination system in Drosophila.

Sex-lethal (Sxl) functions as the switch gene for sex-determination in Drosophila melanogaster by engaging a regulatory cascade. Thus far the origin and evolution of both the regulatory system and SXL protein's sex-determination function have remained largely unknown. In this study, we explore systematically the Sxl homologs in a wide range of insects, including the 12 sequenced Drosophila species, medfly, blowflies, housefly, Megaselia scalaris, mosquitoes, butterfly, beetle, honeybee, ant, and aphid.

Random fluctuation of selection coefficients and the extent of nucleotide variation in human populations.

It is well known that the selection coefficient of a mutant allele varies from generation to generation, and the effect of this factor on genetic variation has been studied by many theoreticians. However, no consensus has been reached. One group of investigators believes that fluctuating selection has an effect of enhancing genetic variation, whereas the other group contends that it has a diversity-reducing effect.

Origins and evolution of microRNA genes in plant species.

MicroRNAs (miRNAs) are among the most important regulatory elements of gene expression in animals and plants. However, their origin and evolutionary dynamics have not been studied systematically. In this paper, we identified putative miRNA genes in 11 plant species using the bioinformatic technique and examined their evolutionary changes.

Roles of mutation and selection in speciation: from Hugo de Vries to the modern genomic era.

One of the most important problems in evolutionary biology is to understand how new species are generated in nature. In the past, it was difficult to study this problem because our lifetime is too short to observe the entire process of speciation. In recent years, however, molecular and genomic techniques have been developed for identifying and studying the genes involved in speciation.

MEGA5: molecular evolutionary genetics analysis using maximum likelihood, evolutionary distance, and maximum parsimony methods.

Comparative analysis of molecular sequence data is essential for reconstructing the evolutionary histories of species and inferring the nature and extent of selective forces shaping the evolution of genes and species. Here, we announce the release of Molecular Evolutionary Genetics Analysis version 5 (MEGA5), which is a user-friendly software for mining online databases, building sequence alignments and phylogenetic trees, and using methods of evolutionary bioinformatics in basic biology, biomedicine, and evolution. The newest addition in MEGA5 is a collection of maximum likelihood (ML) analyses for inferring evolutionary trees, selecting best-fit substitution models (nucleotide or amino acid), inferring ancestral states and sequences (along with probabilities), and estimating evolutionary rates site-by-site.

Evolutionary changes of the target sites of two microRNAs encoded in the Hox gene cluster of Drosophila and other insect species.

MicroRNAs (miRs) are noncoding RNAs that regulate gene expression at the post-transcriptional level. In animals, the target sites of a miR are generally located in the 3' untranslated regions (UTRs) of messenger RNAs. However, how the target sites change during evolution is largely unknown.

Origins and evolution of microRNA genes in Drosophila species.

MicroRNAs (miRs) regulate gene expression at the posttranscriptional level. To obtain some insights into the origins and evolutionary patterns of miR genes, we have identified miR genes in the genomes of 12 Drosophila species by bioinformatics approaches and examined their evolutionary changes. The results showed that the extant and ancestral Drosophila species had more than 100 miR genes and frequent gains and losses of miR genes have occurred during evolution.

The neutral theory of molecular evolution in the genomic era.

The neutral theory of molecular evolution has been widely accepted and is the guiding principle for studying evolutionary genomics and the molecular basis of phenotypic evolution. Recent data on genomic evolution are generally consistent with the neutral theory. However, many recently published papers claim the detection of positive Darwinian selection via the use of new statistical methods.

POPTREE2: Software for constructing population trees from allele frequency data and computing other population statistics with Windows interface.

Currently, there is a demand for software to analyze polymorphism data such as microsatellite DNA and single nucleotide polymorphism with easily accessible interface in many fields of research. In this article, we would like to make an announcement of POPTREE2, a computer program package, that can perform evolutionary analyses of allele frequency data. The original version (POPTREE) was a command-line program that runs on the Command Prompt of Windows and Unix.

Analysis of the immunoglobulin light chain genes in zebra finch: evolutionary implications.

All jawed vertebrates produce immunoglobulins (IGs) as a defense mechanism against pathogens. Typically, IGs are composed of two identical heavy chains (IGH) and two identical light chains (IGL). Most tetrapod species encode more than one isotype of light chains.

Genomic organization and evolution of immunoglobulin kappa gene enhancers and kappa deleting element in mammals.

We have studied the genomic structure and evolutionary pattern of immunoglobulin kappa deleting element (KDE) and three kappa enhancers (KE5', KE3'P, and KE3'D) in eleven mammalian genomic sequences. Our results show that the relative positions and the genomic organization of the KDE and the kappa enhancers are conserved in all mammals studied and have not been affected by the local rearrangements in the immunoglobulin kappa (IGK) light chain locus over a long evolutionary time ( approximately 120 million years of mammalian evolution). Our observations suggest that the sequence motifs in these regulatory elements have been conserved by purifying selection to achieve proper regulation of the expression of the IGK light chain genes.

Genomic drift and evolution of microsatellite DNAs in human populations.

In recent years, copy number variation (CNV) of DNA segments has become a hot topic in the study of genetic variation, and a large amount of CNVs has been uncovered in human populations. The CNVs involving the smallest units of DNA segments are microsatellite DNAs, and the evolutionary change of microsatellite DNAs is believed to occur mostly by the increase or decrease of one repeat unit at a time in a more or less neutral fashion. If we note that eukaryotic genomes contain millions of microsatellite loci, this pattern of nucleotide change is expected to generate random changes of genome size, that is, genomic drift, and will provide a neutral model of CNV evolution.

Reliabilities of identifying positive selection by the branch-site and the site-prediction methods.

Natural selection operating in protein-coding genes is often studied by examining the ratio (omega) of the rates of nonsynonymous to synonymous nucleotide substitution. The branch-site method (BSM) based on a likelihood ratio test is one of such tests to detect positive selection for a predetermined branch of a phylogenetic tree. However, because the number of nucleotide substitutions involved is often very small, we conducted a computer simulation to examine the reliability of BSM in comparison with the small-sample method (SSM) based on Fisher's exact test.

Evolution of F-box genes in plants: different modes of sequence divergence and their relationships with functional diversification.

F-box proteins are substrate-recognition components of the Skp1-Rbx1-Cul1-F-box protein (SCF) ubiquitin ligases. In plants, F-box genes form one of the largest multigene superfamilies and control many important biological functions. However, it is unclear how and why plants have acquired a large number of F-box genes.

The evolution of animal chemosensory receptor gene repertoires: roles of chance and necessity.

Chemosensory receptors are essential for the survival of organisms that range from bacteria to mammals. Recent studies have shown that the numbers of functional chemosensory receptor genes and pseudogenes vary enormously among the genomes of different animal species. Although much of the variation can be explained by the adaptation of organisms to different environments, it has become clear that a substantial portion is generated by genomic drift, a random process of gene duplication and deletion.

Evolutionary redefinition of immunoglobulin light chain isotypes in tetrapods using molecular markers.

The phylogenetic relationships of Ig light chain (IGL) genes are difficult to resolve, because these genes are short and evolve relatively fast. Here, we classify the IGL sequences from 12 tetrapod species into three distinct groups (kappa, lambda, and sigma isotypes) using conserved amino acid residues, recombination signal sequences, and genomic organization of IGL genes as cladistic markers. From the distribution of the markers we conclude that the earliest extant tetrapods, the amphibians, possess three IGL isotypes: kappa, lambda, and sigma.

Origins and evolution of the formin multigene family that is involved in the formation of actin filaments.

In eukaryotes, the assembly and elongation of unbranched actin filaments is controlled by formins, which are long, multidomain proteins. These proteins are important for dynamic cellular processes such as determination of cell shape, cell division, and cellular interaction. Yet, no comprehensive study has been done about the origins and evolution of this gene family.

Ultraconserved coding regions outside the homeobox of mammalian Hox genes.

Background: All bilaterian animals share a general genetic framework that controls the formation of their body structures, although their forms are highly diversified. The Hox genes that encode transcription factors play a central role in this framework. All Hox proteins contain a highly conserved homeodomain encoded by the homeobox motif, but the other regions are generally assumed to be less conserved.

MEGA: a biologist-centric software for evolutionary analysis of DNA and protein sequences.

The Molecular Evolutionary Genetics Analysis (MEGA) software is a desktop application designed for comparative analysis of homologous gene sequences either from multigene families or from different species with a special emphasis on inferring evolutionary relationships and patterns of DNA and protein evolution. In addition to the tools for statistical analysis of data, MEGA provides many convenient facilities for the assembly of sequence data sets from files or web-based repositories, and it includes tools for visual presentation of the results obtained in the form of interactive phylogenetic trees and evolutionary distance matrices. Here we discuss the motivation, design principles and priorities that have shaped the development of MEGA.