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PubMed1991

A simple model of host-parasite evolutionary relationships. Parasitism: compromise or conflict?

The evolutionary biology of host-parasite relationships are considered here using a simple game-theory model in which hosts play against parasite and vice versa. In this model, the players can choose between two strategies (aggressive or not aggressive) and the utility of the game is envisaged in terms of fitness and selective costs. The game solutions suggest that the two types of confrontation are encountered in symbiotic relationships and thus constitute two Evolutionary Stable Strategies (ESS). These observations lead us to discuss: (i) the status of different kinds of symbiotic relationships (i.e. parasitoidism; parasitism, commensalism and mutualism) related to selective costs and (ii) the position of coevolution in this game theory context.

Animals↗

PubMed1992

A stochastic evolutionary model of molecular sequences.

A stochastic evolutionary model of molecular sequences is proposed. The basic forces in evolution are supposed to be mutation and selection. The concept is somewhat similar to Kauffman-Levin's concept of adaptive walks and corresponding analytical expressions have been developed. The selective force is divided into two parts: a slowly-varying part and a rapidly-changing fluctuation. The latter influences the distribution of sequences and results in an equation of motion along the flow line. The former plays a more important role in the emergence of evolutionary order. It is demonstrated that the asymmetry of selective forces would lead to a definite order of the system.

Animals↗

PubMed2002

The role of peroxisomes in the integration of metabolism and evolutionary diversity of photosynthetic organisms.

The peroxisome is a metabolic compartment serving for the rapid oxidation of substrates, a process that is not coupled to energy conservation. In plants and algae, peroxisomes connect biosynthetic and oxidative metabolic routes and compartmentalize potentially lethal steps of metabolism such as the formation of reactive oxygen species and glyoxylate, thus preventing poisoning of the cell and futile recycling. Peroxisomes exhibit properties resembling inside-out vesicles and possess special systems for the import of specific proteins, which form multi-enzyme complexes (metabolons) linking numerous reactions to flavin-dependent oxidation, coupled to the decomposition of hydrogen peroxide by catalase. Hydrogen peroxide and superoxide originating in peroxisomes are important mediators in signal transduction pathways, particularly those involving salicylic acid. By contributing to the synthesis of oxalate, formate and other organic acids, peroxisomes regulate major fluxes of primary and secondary metabolism. The evolutionary diversity of algae has led to the presence of a wide range of enzymes in the peroxisomes that are only similar to higher plants in their direct predecessors, the Charophyceae. The appearance of seed plants was connected to the acquirement by storage tissues, of a peroxisomal fatty acid oxidation function linked to the glyoxylate cycle, which is induced during seed germination and maturation. Rearrangement of the peroxisomal photorespiratory function between different tissues of higher plants led to the appearance of different types of photosynthetic metabolism. The peroxisome may therefore have played a key role in the evolutionary formation of metabolic networks, via establishing interconnections between different metabolic compartments.

Biological Evolution↗

PubMed1999

Evolutionary conservation of circulating soluble low density lipoprotein receptor-related protein-like ("LRP-like") molecules.

Low density lipoprotein receptor family members characteristically bind 39-kDa receptor associated protein (RAP). Soluble forms of these receptors have been described in humans including the 515/85-kDa dimeric receptor, low density lipoprotein receptor-related protein (LRP/alpha2MR), which is involved in multiple processes including lipoprotein and protease metabolism. Here we demonstrate evolutionary conservation in the generation of these soluble RAP-binding proteins of high molecular weight, by identifying their presence in mammalian, avian, and reptilian sera as well as in the circulating haemolymph of a mollusc. Sera extracted on immobilized RAP, produced bands at approximately 500 kDa in radiolabeled ligand blots by using the LRP/alpha2MR-specific ligand, Pseudomonas exotoxin A (PEA). These findings suggest that circulating RAP-binding proteins with high molecular weight in vertebrates share features of LRP/alpha2MR (LRP-like molecules). RAP-binding molecules in the mammalian serum extracts were further characterized as LRP/alpha2MR homologues in Western blots by using antibodies against the 515-kDa alpha-chain of LRP/alpha2MR. Western blots of mammalian serum extracts using two monoclonal antibodies recognizing the 85-kDa transmembrane beta-chain suggested that a portion of the beta-chain's ectodomain remains associated with the alpha-chain, but the beta-chain's intracellular carboxy terminus is absent. These results are consistent with evolutionary conservation in the generation, composition, and ligand-binding ability of soluble LRP-like receptors and suggest that their presence is a necessary aspect of the receptor's function.

Animal Population Groups↗

PubMed2002

Evolutionary behavioral genetics in Drosophila.

Behavioral genes have a special evolutionary interest because they are potentially involved in speciation and in many forms of adaptation. Dozens of loci affecting different aspects of behavior have been already identified and cloned in Drosophila. Some of these genes determine variation in such ethologically complex phenotypes as the male "love song" that is produced during courtship and the locomotor "sleep-wake" activity cycles that are controlled by the circadian clock. Although the evolutionary analysis of most behavioral genes in Drosophila is relatively new, it has already given important insights into the forces shaping the molecular variation at these loci and their functional consequences.

Amino Acid Sequence↗

PubMed2003

Inference of viral evolutionary rates from molecular sequences.

The processes of mutation and nucleotide substitution contribute to the observed variability in virulence, transmission and persistence of viral pathogens. Since most viruses evolve many times faster than their human hosts, we are in the unusual position of being able to measure these processes directly by comparing viral genes that have been isolated and sequenced at different points in time. The analysis of such data requires the use of specific statistical methods that take into account the shared ancestry of the sequences and the randomness inherent in the process of nucleotide substitution. In this paper we describe the various statistical methods for estimating evolutionary rates, which can be classified into three general approaches: linear regression, maximum likelihood, and Bayesian inference. We discuss the advantages and shortcomings of each approach and illustrate their use through the analysis of two example viruses; human immunodeficiency virus type 1 and dengue virus serotype 4. Reliable estimates of viral substitution rates have many important applications in population genetics and phylogenetics, including dating evolutionary events and divergence times, estimating demographic parameters such as population size and generation time, and investigating the effect of natural selection on molecular evolution.

Base Sequence↗

PubMedDate not supplied

Evolutionary origins of mechanosensitive ion channels.

According to the recent revision, the universal phylogenetic tree is composed of three domains: Eukarya (eukaryotes), Bacteria (eubacteria) and Archaea (archaebacteria). Mechanosensitive (MS) ion channels have been documented in cells belonging to all three domains suggesting their very early appearance during evolution of life on Earth. The channels show great diversity in conductance, selectivity and voltage dependence, while sharing the property of being gated by mechanical stimuli exerted on cell membranes. In prokaryotes, MS channels were first documented in Bacteria followed by their discovery in Archaea. The finding of MS channels in archaeal cells helped to recognize and establish the evolutionary relationship between bacterial and archaeal MS channels and to show that this relationship extends to eukaryotic Fungi (Schizosaccharomyces pombe) and Plants (Arabidopsis thaliana). Similar to their bacterial and archaeal homologues, MS channels in eukaryotic cell-walled Fungi and Plants may serve in protecting the cellular plasma membrane from excessive dilation and rupture that may occur during osmotic stress. This review summarizes briefly some of the recent developments in the MS channel research field that may ultimately lead to elucidation of the biophysical and evolutionary principles underlying the mechanosensory transduction in living cells.

Amino Acid Sequence↗

PubMed1987

Generalised osteoarthritis: an evolutionary problem?

Polyarticular osteoarthritis (OA) has a distinctive pattern of joint involvement. Some joints, such as the first metatarsophalangeal joint, are commonly affected, whereas others, such as the shoulder, are rarely involved. This distinct pattern of involvement may represent a subset of OA--generalised OA. Analysis of the pattern of change in joint function in the recent evolutionary development of man suggests a hypothesis that explains the pattern of joint involvement in generalised OA. Joints most commonly affected have undergone recent rapid evolutionary change to a new function that has resulted in increased loading. These joints are therefore relatively underdesigned, have little functional reserve, and are likely to fail often and early. Joints that are rarely affected have changed to a function with reduced loading. They are relatively overdesigned and have a large functional reserve, so fail rarely and late.

Biological Evolution↗

PubMed1998

An evolutionary approach to behavioral pharmacology: using drugs to understand proximate and ultimate mechanisms of different forms of aggression in mice.

Psychoactive drugs (Fluprazine and Chlordiazepoxide--CDP) were used as probes to test both differences or similarities in neurochemical substrates (proximal causations) and adaptive significance (ultimate causations) of different forms of intraspecific aggression in wild mice and laboratory Swiss CD-1 counterparts. Fluprazine (1-5 mg/kg) inhibited maternal attack on female, but not on male intruders. Thus, phenotypically different attack behaviors (offence and defence respectively) which have different functions may be modulated by different neurochemical substrates. Intrasexual attack and infanticide which are phenotypically different, but share similar functions (i.e. competition for mates and resources) were equally inhibited by Fluprazine (2 mg/kg) both in males and females of wild and laboratory mice. This indicates that the neural substrates of these behaviors are related and similarly regulated in the two sexes. Fluprazine was used to test the prediction of the evolutionary model on fighting strategies in male-male asymmetric contests as far as fighting ability and resource value (mating and cohabitation with a female) are concerned. Fluprazine inhibited the intensity of fighting (i.e. more 'defensive' behavioral phenotype of attack) only in animals without previous positive fighting experience, suggesting that different behavioral strategies are based on different neurochemical modulation. Experience of attack also influenced the effects of CDP (2.5-5 mg/kg) in both lactating females and male resident mice. The reported proaggressive effects of benzodiazepines were observed only in animals with prior fighting experience in both cases. Thus the understanding of the effects of drugs on behavior demands consideration of the biological variability (e.g. genetic, previous experience and/or interindividual differences) and the adaptive significance of behavior in the experimental context. On this background ethopharmacology can be defined as an evolutionary approach to the study of a drugs effect on neurochemical mechanisms and functions of behavior.

Aggression↗

PubMed2002

Toward a revised evolutionary adaptationist analysis of depression: the social navigation hypothesis.

Evolutionary biologists use Darwinian theory and functional design ("reverse engineering") analyses, to develop and test hypotheses about the adaptive functions of traits. Based upon a consideration of human social life and a functional design analysis of depression's core symptomatology we offer a comprehensive theory of its adaptive significance called the Social Navigation Hypothesis (SNH). The SNH attempts to account for all intensities of depression based on standard evolutionary theories of sociality, communication and psychological pain. The SNH suggests that depression evolved to perform two complimentary social problem-solving functions. First, depression induces cognitive changes that focus and enhance capacities for the accurate analysis and solution of key social problems, suggesting a social rumination function. Second, the costs associated with the anhedonia and psychomotor perturbation of depression can persuade reluctant social partners to provide help or make concessions via two possible mechanisms, namely, honest signaling and passive, unintentional fitness extortion. Thus it may also have a social motivation function.

Adaptation, Psychological↗

PubMed1998

Divergent evolutionary constraints on mitochondrial and nuclear genomes of malaria parasites.

Genetic variation among malaria parasites has important consequences with regard to drug resistance, pathogenicity, immunity, transmission, and speciation. In this regard, malaria parasites have been shown to display a high degree of inter- and intra-species genetic divergence. The nuclear genomes of Plasmodium falciparum, Plasmodium yoelii, and Plasmodium gallinaceum are vastly divergent yet share a similar codon usage and total A/T content of approximately 82%. This is in contrast to other primate-specific species including P. vivax which have an A/T content of approximately 67%. To assess the effects of this evolutionary divergence on the conservation of gene content, organization, and codon usage in the mitochondrial DNA (mtDNA) of malaria parasites, we have cloned and sequenced the mitochondrial genome of Plasmodium vivax, and compared it with the mtDNAs of P. falciparum, P. yoelii, and P. gallinaceum. The P. vivax mitochondrial genome was found to be 5990 base pairs in length, and displayed a gene organization identical to that of P. falciparum, P. yoelii, and P. gallinaceum. Furthermore, there was a remarkable 90% conservation of sequence identity between the mitochondrial genomes of all four species. As an example of intra-species conservation, comparison of mtDNAs from two independently cloned P. falciparum isolates, Malay Camp and C10, revealed only a single nucleotide substitution. A/T content of the P. vivax mitochondrial genome was found to be identical to other species of Plasmodium, hence, we have postulated that the mitochondrial genomes of malaria parasites were refractory to the evolutionary shifts in nucleotide content seen among the nuclear genomes of malaria parasites. Among different Plasmodium species, the second position of mitochondrial codons were found to be the least prone to substitutions and displayed a significant bias in pyrimidines. These aspects of mitochondrial codon usage were distinct from the nuclear genome and may reflect functional aspects of decoding by the mitochondrial translational system.

Amino Acid Sequence↗

PubMed1998

Neuropeptide families: evolutionary perspectives.

Examination of neuropeptide families can provide information about phyletic relationships and evolutionary processes. In this article the oxytocin/vasopressin family, growth hormone releasing factor (GRF) superfamily and the substance P/tachykinin family have been considered in detail because they have been isolated from an extraordinarily diverse array of species from several vertebrate classes and invertebrate phyla. More important is that the nucleotide sequence of mRNA or cDNA encoding many of these peptides has been determined, which has allowed evolutionary distances to be estimated based on the DNA mutation rate. The origin of a given family lies in a primordial gene that arose many millions of years ago, and through time, exon duplication and insertion, gene duplication, point mutation and exon loss, the family developed into the forms that are now recognised. For example, in birds, GRF and pituitary adenylate cyclase activating peptide (PACAP) are encoded by the same gene, which probably arose as a result of exon duplication and tandem insertion of the ancestral GRF gene. In mammals GRF is the sole product on one gene, and PACAP is the product of a gene that also produces PACAP-related peptide (PRP), which is homologous to GRF. Thus it appears that between birds and mammals the GRF/PACAP gene duplicated: exon loss gave rise to the mammalian GRF gene, while mutation led to the formation of the mammalian PRP/PACAP gene. The neuropeptide Y superfamily is considered briefly, as is cionin, which is an invertebrate peptide that is closely related to the mammalian gastrin/cholecystokinin family.

Amino Acid Sequence↗

PubMed1996

The cloning and sequencing of a ribosomal L18 protein from an evolutionary divergent eukaryote, Trypanosoma brucei.

Eukaryotic ribosomal proteins are highly conserved across widely divergent species, suggesting that strong functional constraints prevent divergence of important amino acid motifs. Using this as a basis, an evolutionary approach could be used to identify putative functional motifs. We obtained the DNA sequence of the ribosomal protein L18 from the evolutionary divergent protozoan parasite, Trypanosoma brucei. Analysis of this sequence showed that it had 46% and 43% identity with the human and yeast sequences, respectively, and 30% of amino acid residues were identical across all the species analysed. Using these data, amino acids essential to the structure and function of ribosomal protein L18 can be inferred and could provide valuable information for molecular modelling and mutational studies.

Amino Acid Sequence↗

PubMed2001

Evolutionary expansion of CRIB-containing Cdc42 effector proteins.

Cdc42, a small GTPase, regulates actin polymerization and other signaling pathways through interaction with many different downstream effector proteins. Most of these effector proteins contain a Cdc42-binding domain, called a CRIB domain. Here, we describe the evolutionary analysis of these CRIB-containing proteins in yeast, worms, flies and humans. The number of CRIB-containing effector proteins increases from yeast to humans, involving both an increase within families and the emergence of new families. These evolutionary changes correlate with the development of the more complex signaling pathways present in higher organisms.

Animals↗

PubMed2003

Evolutionary consequences of Wolbachia infections.

The past decade has revealed the bacterium Wolbachia as the most widespread symbiont of arthropods and nematodes. Behind this evolutionary success is an remarkable variety of effects on host biology, ranging from manipulation of reproduction in favor of females to more classical mutualistic interactions. Here we discuss the potential of Wolbachia for promoting evolutionary changes in its hosts.

Animals↗

PubMed2003

An evolutionary approach reveals a high protein-coding capacity of the human genome.

We developed a new evolutionary method for identifying exons from genomic sequences and found 19000 potential coding exons that are absent from all existing annotations of the human genome. Of these, 13700 satisfied very stringent criteria and can with confidence be considered as novel exons. Evidently, a large number of new human genes can be identified using evolutionary approaches.

Animals↗

PubMed1999

Evolutionary change in the functional specificity of genes.

Species throughout the animal kingdom share not only housekeeping but also many key regulatory genes. Nonetheless, species differ from one another developmentally and thus, also morphologically. One of the general aims of comparative developmental genetics is to understand how similar molecules can generate the known diversity of biological form. Here, we argue that gene function can change in different ways during the evolution of developmental processes. Genes can be recruited to serve completely new functions in a new regulatory linkage (co-option), they can change their molecular specificity while remaining in the original (homologous) developmental program and can, at the same time, retain other functions. We describe evidence for such evolutionary patterns based on the comparison of loss-of-function mutations of homologous genes of the two free-living nematodes Caenorhabditis elegans and Pristionchus pacificus. Ultimately, it is the interplay of conservation and change of the specificity of genes and genetic networks that generates developmental novelty over evolutionary time.

Animals↗

PubMed2000

Transgenic organisms in evolutionary ecology.

Evolutionary ecology aims to understand how phenotypes are designed for reproductive success and survival. Perhaps the most powerful approach towards this goal is to alter a character genetically and observe the resulting change in reproduction, survival, growth, defense or competitive ability. Until recently, this strategy was not practical. Transgenic manipulation now offers a solution - novel genes are introduced into the germ line and are then expressed in the developing organism. This technique is already available in model and agricultural organisms. The challenge for molecular evolutionary ecologists is to find ways to adopt these powerful systems to understand the mechanisms underlying adaptive traits and their evolution.

Journal Article↗