Scientists Trace Origin and Evolution of GPCR Kinases

20 03 2012

G protein-coupled receptor (GPCR) kinases (GRKs) are important in regulating many signaling pathways in the bodies of animals.  Both under and over regulation of GRKs has been implicated in a variety of human illnesses, including heart disease, Parkinson’s disease, and depression.

Reporting in an article published on March 19, in the online journal PLoS One (Public Library of Science One), a team of scientists from the United States has traced the origins and evolution of these kinases.  Based on their study, the team concludes that GPCRs are very old, having appeared before the rise of Metazoa and expanded rapidly among true metazoans.  They hypothesize that this rapid expansion was the result of the need for quick signalling adjustments in fast-moving animals.  They note that this “lifestyle requires the ability to reset and re-engage the environmental sensors frequently, which calls for [a] rapid shut-off mechanism.  A dedicated system for quick deactivation of GPCR may have been one of the factors profoundly determining the metazoan lifestyle.”  For the full paper, see here.

G Protein-Coupled Receptor Kinase

Crystal structure of G protein coupled receptor kinase 1 (GRK1) bound to ATP (Credit: Image is from Wikipedia Commons and is by the Jmol development team. It is used under a GNU Free License.)

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New Genus and Species of Pterosaur Discovered in Morocco

27 05 2010

An international team of paleontologists has discovered a new genus and species of pterosaur in the Kem Kem formation of southeastern Morocco.  Published May 26, in the online journal Public Library of Science One (PLoS One), it is named Alanqa saharica, and according to the authors is “the first clear evidence for the presence of azhdarchids in Gondwana at the start of the Late Cretaceous.”

The remains discovered at the site, along with other specimens now ascribed to the new species, represent animals with wingspans of approximately three to four meters.  However, a vertebra discovered that probably belongs to the same species indicates that a wingspan of six meters was possible.

The discovery adds to our knowledge of pterosaurs from Africa, which has been severely limited until recently, and even now is represented only by a number of fragmentary specimens.

The article can be read in its entirety at the following link: 
http://www.plosone.org/article/info:doi/10.1371/journal.pone.0010875.





Simulation Study Indicates “Non-Negligible” Natural Selection on Alleles Affecting Human Longevity and Late-Life Disease

5 04 2010

This article, by Fotios Drenos and Thomas B. L. Kirkwood, both of the Institute for Ageing and Health at Newcastle University, Newcastle Upon Tyne, Tyne, United Kingdom, that appeared on March 31, 2010, in the online journal PloS One, uses computer simulation to show that the effects of natural selection on genes affecting health in old age can be significant.  Below is the abstract from the article.  To read the complete article, please see the following URL:  http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0010022.

Abstract

It is often claimed that genes affecting health in old age, such as cardiovascular and Alzheimer diseases, are beyond the reach of natural selection. We show in a simulation study based on known genetic (apolipoprotein E) and non-genetic risk factors (gender, diet, smoking, alcohol, exercise) that, because there is a statistical distribution of ages at which these genes exert their influence on morbidity and mortality, the effects of selection are in fact non-negligible. A gradual increase with each generation of the ε2 and ε3 alleles of the gene at the expense of the ε4 allele was predicted from the model. The ε2 allele frequency was found to increase slightly more rapidly than that for ε3, although there was no statistically significant difference between the two. Our result may explain the recent evolutionary history of the epsilon 2, 3 and 4 alleles of the apolipoprotein E gene and has wider relevance for genes affecting human longevity.





Scientists use Mitochondrial DNA to Identify Recently Diverged Mouse Lemur Lineages

5 04 2010
This image is copyrighted under the creative commons attribution license by Weisrock D.W., Rasoloarison R.M., Fiorentino I., Ralison J.M., Goodman S.M., et al. (2010) for the article “Delimiting Species without Nuclear Monophyly in Madagascar's Mouse Lemurs”. Appearing in PLoS ONE 5(3): e9883. doi:10.1371/journal.pone.0009883.

The island of Madagascar, showing the areas of sampling used in this study.

An international team of researchers has used mitochondrial DNA (mtDNA) to help distinguish between a group of Madagascar Mouse Lemurs who have recently begun to diverge.

One of the issues associated with delineating species that have recently diverged from common ancestors is that often there has not been sufficient time for the usual cues of speciation, such as morphological differences, reproductive isolation, and monophyly within the gene tree to have become settled and readily evident.  Writing in the online journal, PLoS One, seven scientists from the United States, Germany, and Madagascar used multiple lines of evidence from mtDNA and nuclear DNA (nDNA) to identify “cryptically diverged” population-level mouse lemur lineages from throughout Madagascar.  It is believed to represent the most thorough sample of mouse lemur species ever conducted.

The result was the identification of a large number of geographically-defined clades.  These were strongly supported by the initial mtDNA evidence, as well as additionally supported by nDNA patterns.  The clades thus identified, are also supported by population divergence estimates based on genealogical exclusivity estimates.  The paper concludes that “Mouse lemur lineage diversity is reflected in both a geographically fine-scaled pattern of population divergence within established and geographically widespread taxa, as well as newly resolved patterns of micro-endemism revealed through expanded field sampling into previously poorly and well-sampled regions.”

For more information, please see the original article at the following URL: http://www.plosone.org/article/info:doi/10.1371/journal.pone.0009883





Energy Expenditure and Body Composition in Two Sympatric Lemurs does NOT Support Theories Accounting for Unusual Socio-Ecological Traits and Life History Features

27 03 2010
This image is from Wikimedia Commons and is in the Public Domain

Lemur Catta, also known as the Ring-tailed Lemur

In an article published March 25, in the Online journal PLoS one, researchers present evidence showing no support for the theory that energy conservation behaviors and mechanisms are the result of evolutionary adaptation in response to unusual socio-ecological traits and life history features of those species.

Following is the abstract from the article.  For the complete article, please see the following URL:
http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0009860.

Abstract

Background

Evolutionary theories that account for the unusual socio-ecological traits and life history features of group-living prosimians, compared with other primates, predict behavioral and physiological mechanisms to conserve energy. Low energy output and possible fattening mechanisms are expected, as either an adaptive response to drastic seasonal fluctuations of food supplies in Madagascar, or persisting traits from previously nocturnal hypometabolic ancestors. Free ranging ring-tailed lemurs (Lemur catta) and brown lemurs (Eulemur sp.) of southern Madagascar have different socio-ecological characteristics which allow a test of these theories: Both gregarious primates have a phytophagous diet but different circadian activity rhythms, degree of arboreality, social systems, and slightly different body size.

Methodology and Results

Daily total energy expenditure and body composition were measured in the field with the doubly labeled water procedure. High body fat content was observed at the end of the rainy season, which supports the notion that individuals need to attain a sufficient physical condition prior to the long dry season. However, ring-tailed lemurs exhibited lower water flux rates and energy expenditure than brown lemurs after controlling for body mass differences. The difference was interpreted to reflect higher efficiency for coping with seasonally low quality foods and water scarcity. Daily energy expenditure of both species was much less than the field metabolic rates predicted by various scaling relationships found across mammals.

Discussion

We argue that low energy output in these species is mainly accounted for by low basal metabolic rate and reflects adaptation to harsh, unpredictable environments. The absence of observed sex differences in body weight, fat content, and daily energy expenditure converge with earlier investigations of physical activity levels in ring-tailed lemurs to suggest the absence of a relationship between energy constraints and the evolution of female dominance over males among lemurs. Nevertheless, additional seasonal data are required to provide a definitive conclusion.





Scientist Shows Post-Mating Pre-Fertilization Barrier to Cross Species Breeding

25 03 2010

Daniel R. Matute of the department of ecology and evolution at the University of Chicago has published a study of two species of Drosophila, that show, for as far as I am aware the first time, the presence of postmating prezygotic isolation.  Specifically, that means a barrier or barriers that act after mating but before fertilization.

The paper appeared on March 23, in the online journal Public Library of Science (PLoS) Biology.  It is important from an evolutionary standpoint as a demonstration of the diversity of ways that reinforcement by gametic isolation can bolster isolation between species or proto-species.

Following is the abstract from the paper.  For the complete paper, please see the following URL:  http://www.plosbiology.org/article/info%3Adoi%2F10.1371%2Fjournal.pbio.1000341.

Abstract

Reinforcement, a process by which natural selection increases reproductive isolation between populations, has been suggested to be an important force in the formation of new species. However, all existing cases of reinforcement involve an increase in mate discrimination between species. Here, I report the first case of reinforcement of postmating prezygotic isolation (i.e., barriers that act after mating but before fertilization) in animals. On the slopes of the African island of São Tomé, Drosophila yakuba and its endemic sister species D. santomea hybridize within a well-demarcated hybrid zone. I find that D. yakuba females from within this zone, but not from outside it, show an increase in gametic isolation from males of D. santomea, an apparent result of natural selection acting to reduce maladaptive hybridization between species. To determine whether such a barrier could evolve under laboratory conditions, I exposed D. yakuba lines derived from allopatric populations to experimental sympatry with D. santomea, and found that both behavioral and gametic isolation become stronger after only four generations. Reinforcement thus appears to be the best explanation for the heightened gametic isolation seen in sympatry. This appears to be the first example in animals in which natural selection has promoted the evolution of stronger interspecific genetic barriers that act after mating but before fertilization. This suggests that many other genetic barriers between species have been increased by natural selection but have been overlooked because they are difficult to study.





Recent Study May have Implications for Invasion-Related Concepts in Evolutionary Theory

18 03 2010
This image is by Bruce Marlin and is courtesy of Wikimedia Commons.  It is licensed under the Creative Commons Attribution-Share Alike 2.5 Generic license.

Harmonia axyridis, also known as the Lady Bug and the Harlequin Ladybird

A recent article in PLoS One hypothesis a “bridgehead” effect in certain, highly successful, invasive species that allow them to use one invasion as a staging ground to mount additional invasions.  Following is the original abstract for the article, along with a link to the entire piece:

Abstract

Recent studies of the routes of worldwide introductions of alien organisms suggest that many widespread invasions could have stemmed not from the native range, but from a particularly successful invasive population, which serves as the source of colonists for remote new territories. We call here this phenomenon the invasive bridgehead effect. Evaluating the likelihood of such a scenario is heuristically challenging. We solved this problem by using approximate Bayesian computation methods to quantitatively compare complex invasion scenarios based on the analysis of population genetics (microsatellite variation) and historical (first observation dates) data. We applied this approach to the Harlequin ladybird Harmonia axyridis (HA), a coccinellid native to Asia that was repeatedly introduced as a biocontrol agent without becoming established for decades. We show that the recent burst of worldwide invasions of HA followed a bridgehead scenario, in which an invasive population in eastern North America acted as the source of the colonists that invaded the European, South American and African continents, with some admixture with a biocontrol strain in Europe. This demonstration of a mechanism of invasion via a bridgehead has important implications both for invasion theory (i.e., a single evolutionary shift in the bridgehead population versus multiple changes in case of introduced populations becoming invasive independently) and for ongoing efforts to manage invasions by alien organisms (i.e., heightened vigilance against invasive bridgeheads).

Read the entire article by following this link:
http://www.plosone.org/article/info:doi/10.1371/journal.pone.0009743