The making of gametes in higher plants

Boavida, L. ; Becker, J.D. ; Feijó, J.A.

Plants/cytology/genetics/growth & development ; pollen ; embryo sac ; gametogenesis ; microsporogenesis ; macrosporogenesis

Higher plants have evolved to be one of the predominant life forms on this planet. A great deal of this evolutionary success relies in a very short gametophytic phase which underlies the sexual reproduction cycle. Sexual plant reproduction takes place in special organs of the flower. In most species the processes of gametogenesis, pollination, syngamy and embryogenesis are sequentially coordinated to give rise to a functional seed in a matter of few weeks. Any of these processes ...

UBC Press

2005

info:eu-repo/semantics/article

en

open access

The Ypt/Rab family and the evolution of trafficking in Fungi

Pereira-Leal, J.B.

Fungal Proteins/genetics/metabolism ; Fungi/classification/metabolism ; Rab GTP-Binding Proteins/genetics/metabolism ; Evolution ; Fungi ; Protein traffic ; Rab GTPases

The evolution of the eukaryotic endomembrane system and the transport pathways of their vesicular intermediates are poorly understood. A common set of organelles and pathways seems to be present in all free-living eukaryotes, but different branches of the tree of life have a variety of diverse, specialized organelles. Rab/Ypt proteins are small guanosine triphosphatases with tissue-specific and organelle-specific localization that emerged as markers for organelle diversity. Here, ...

Wiley-Blackwell

2008

info:eu-repo/semantics/article

en

open access

Modularity: Understanding the Development and Evolution of Natural Complex Systems

Pereira-Leal, J.B.

Springer

2006

info:eu-repo/semantics/review

en

open access

Small-word networks decrease the speed of Muller's ratchet

Combadão, J. ; Dionisio, F. ; Campos, P.R.A. ; Gordo, I. ; Gomes, M.G.M.

Evolution ; Extinction, Biological ; Models, Genetic ; Selection, Genetic

Muller's ratchet is an evolutionary process that has been implicated in the extinction of asexual species, the evolution of non-recombining genomes, such as the mitochondria, the degeneration of the Y chromosome, and the evolution of sex and recombination. Here we study the speed of Muller's ratchet in a spatially structured population which is subdivided into many small populations (demes) connected by migration, and distributed on a graph. We studied different types of networks: ...

2007-05-22

info:eu-repo/semantics/article

en

open access

The reinfection threshold regulates pathogen diversity: the case of influenza

Gokaydin, D. ; Oliveira-Martins, J.B. ; Gordo, I. ; Gomes, M.G.M.

Antigenic Variation/genetics/immunology ; Disease Outbreaks/statistics & numerical data ; Disease Transmission, Infectious/statistics & numerical data ; Genetic Variation/genetics ; Influenza A virus/genetics/immunology ; Influenza, Human/epidemiology/genetics/immunology ; Models, Immunological

The awareness that pathogens can adapt and evolve over relatively short time-scales is changing our view of infectious disease epidemiology and control. Research on the transmission dynamics of antigenically diverse pathogens is progressing and there is increasing recognition for the need of new concepts and theories. Mathematical models have been developed considering the modelling unit in two extreme scales: either diversity is not explicitly represented or diversity is represented ...

2007-02-22

info:eu-repo/semantics/article

en

open access

Pathogen genetic variation in small-world host contact structures

Campos, P.R.A. ; Gordo, I.

Complex Networks ; Dynamics ; Evolution ; models for evolution (theory) ; mutational and evolutionary processes ; population dynamics (theory)

We introduce a model for assessing the levels and patterns of genetic diversity in pathogen populations, whose epidemiology follows a susceptible– infected–susceptible model. We assume a population which is structured into many small subpopulations (hosts) that exchange migrants (transmission) between their neighbours. We consider that the hosts are connected according to a small-world network topology, and in this way our model interpolates between two classical population genetics ...

IOP Science

2006-12-22

info:eu-repo/semantics/article

en

open access

Controlling excludability in the evolution of cooperation

Dionisio, F. ; Gordo, I.

Evolution of complexity ; Excludability ; Multi-level selection ; Privatization ; Rivalry ; Tragedy of the commons ; Kin selection model ; Collective action ; Multilevel selection ; Social evolution ; Commons ; Tragedy ; Transitions ; Competition ; Repression

Background: A tragedy of the commons arises if individuals cannot protect their future use of a depletable resource, and individual fitness increases if individuals exploit the resource at rates beyond sustainability. Natural selection then forces the individuals to diminish, perhaps even to destroy, their resource. One way to protect future use is privatization - that is, locally excluding rivals from the resource. Another is to reduce rivalry among individuals by restricting ...

2007

info:eu-repo/semantics/article

en

open access

Did Germinal Centers evolve under differential effects of diversity vs affinity?

Fero, J. ; Combadão, J. ; Gordo, I.

Mullers Ratchet

The classical view on the process of mutation and affinity maturation that occurs in GCs assumes that their major role is to generate high affinity levels of serum Abs, as well as a dominant pool of high affinity memory B cells, through a very efficient selection process. Here we present a model that considers different types of structures where a mutation selection process occurs, with the aim at discussing the evolution of Germinal Center reactions. Based on the results of this ...

Springer

2006

info:eu-repo/semantics/article

en

open access

Nonequilibrium model for estimating parameters of deleterious mutations

Gordo, I. ; Dionisio, F.

Evolution ; Genetic Variation/genetics ; Genetics, Population/methods ; Models, Genetic ; Mutation/genetics ; Population Dynamics ; Selection, Genetic

Deleterious mutations are of extreme evolutionary importance because, even though they are eliminated by natural selection, their continuous pressure creates a pool of variability in natural populations. They are of potential relevance for the existence of several features in evolution, such as sexual reproduction, and pose a risk to small asexual populations. Despite their extreme importance, the deleterious mutation rate and the effects of each mutation on fitness are poorly ...

American Physical Society

2005-03-18

info:eu-repo/semantics/article

en

open access

Adaptation of asexual populations under Muller’s ratchet

Bachtrog, D. ; Gordo, I.

Adaptation, Physiological ; Evolution ; Genetics, Population ; Models, Biological ; Background selection ; Genetic hitchhiking ; Muller’s ratchet ; Rate of adaptation

We study the population genetics of adaptation in nonequilibrium haploid asexual populations. We find that the accumulation of deleterious mutations, due to the operation of Muller’s ratchet, can considerably reduce the rate of fixation of advantageous alleles. Such reduction can be approximated reasonably well by a reduction in the effective population size. In the absence of Muller’s ratchet, a beneficial mutation can only become fixed if it creates the best possible genotype; ...

2004-07

info:eu-repo/semantics/article

en

open access