Now that President Obama's in the White House, he's rolling out changes - closing Guantanamo Bay, permitting Federal funding for agencies that publicise abortion, and now enabling Federal funding for stem cell research.

Perhaps related to the thaw in stem cell research, the US Food and Drug Administration has approved a proposal aimed at investigating the use of embryonic stem cell therapy in spinal injury (BBC News).  The proposal, from Geron Corp., has been approved.

Many tropical diseases are transmitted by insect vectors - malaria (which is caused by Plasmodium parasites) and yellow fever (caused by a virus) being examples of diseases transmitted by Anopheles and Aedes mosquitoes respectively.  Dengue fever is another viral disease that is transmitted by Aedes aegypti.  One crucial feature of the disease transmission cycle is that once the disease organism is collected by the mosquito in a blood meal, it takes some time to develop within the insect before it becomes infectious.  In the case of both malaria and dengue fever, this period of time is about two weeks.  This paper evaluates the use of the endosymbiotic bactera Wolbachia to shorten mosquito lifespan in the hope that this will reduce disease transmission.

In a sense, this is an attractive strategy, and one that makes use of one of the properties of some Wolbachia strains to shorten host lifespan. I have previously blogged about some aspects of Wolbachia biology in the immune system of insects.  Wolbachia infection is maternally transmitted, and spreads through insect populations because of a reproductive drive known as cytoplasmic incompatibility (CI) - infected females mated to uninfected males yield infected offspring, while uninfected females mated to infected males yield no offspring.  This reproductive drive is presumably sufficient to drive even strains of Wolbachia which have negative effects on viability (such as reduced lifespan) through the population.

The journal Science has launched a new blog to celebrate the Darwin 200 anniversary, entitled Origins. There's an rss feed.

In the current issue of the journal are articles by Peter Bowler on Darwin's Originality and by Carl Zimmer entitled On the Origin of Life on Earth. [subscription may be required].

I picked up on this new blog at ScienceBlogs - "Blogging the Origin" via Science's Origins blog.  In this blog, science writer and evolutionist John Whitfield, who bravely admits to never having read The Origin of Species before, is conducting a book club cum blog as he reads the text, chapter by chapter in this anniversary year.  As I write, he's covered the Introduction and Chapters 1 and 2, with the next instalment due on Friday.  He plans to finish in time to celebrate Darwin's 200th birthday.

I haven't read The Origins since I was a teenager (which is an upsettingly long time ago), and this has inspired me to read it again.  But which version?   The old Pelican paperback edition I read all those years ago is a later edition of the tome, while the edition reprinted in the compilation From So Simple a Beginning", edited by E. O. Wilson, is I think the first edition (but lacks a certain portability - the volume also has Voyage of the Beagle, Descent of Man and The Expression of Emotions, all in a hardback binding).  Perhaps I should limit myself to the 1858 pair of papers by Darwin and Wallace?

I see from the BBC news site that panda diplomacy is on again - China has gifted two giant pandas to Taiwan.  I admit that giant pandas are cute, and have the interesting novelty of a extra digit (the "Panda's Thumb") that is derived from a modified sesamoid bone.  But, really, a carnivore that subsists on a diet that is 99% bamboo, that cannot digest cellulose, and which needs to consume 9-14 kg of bamboo shoots a day has been dealt a rather unfortunate hand!

On the other hand, this YouTube video never fails to make me laugh:

The Royal Mail has issued (or will issue) stamps to celebrate the upcoming Darwin anniversary.  There's also a miniature sheet, depicting the Galapagos Islands, and a variety of the specialised fauna found there.

I think they are particularly attractive, and it's good to see the profile of this most important of anniversaries maintained.  For more information, visit Norvic Philatelics - there is a much more information on the design, background information, and how to buy first day covers etc (and I also linked to their images).  I have to say, I never thought I'd blog about postage stamps, but there you go!

[Post edited to remove direct links to the images]

Of the many questions in evolutionary biology, the genetic basis of reproductive isolation between species and subspecies is a pretty hot topic. Drosophila pseudoobscura is a new world Drosophila species that has been used in evolutionary biology studies for many years.  This paper looks at the genetic basis of the hybrid sterility and segregation distortion seen in crosses between two subspecies, D. pseudoobscura pseudoobscura (referred to as "USA") and D. pseudoobscura bogotana (referred to as "Bogota"). It's a nice illustration of the impact of the 12 Drosophila genome sequences now available - D. pseudoobscura was the second Drosophila species to have its genome sequenced.

There is only partial reproductive isolation between these subspecies - male progeny from Bogota females crossed with USA males are virtually sterile (though when aged, they apparently yield offspring, though with a distorted sex ratio indicative of segregation distortion).  The female siblings are fertile, as are the offspring of a cross performed between UAS females crossed with Bogota males.  The two subspecies therefore obey Haldane's Rule.

Yet another palaeontology blog post!  This story roared round the internet just before Christmas (for example the BBC News story), but I found it interesting as a non-specialist in arachnid evolution or palaeontology, partly because of the methods used for extracting fossil arthropod material from the substrate, and partly because it tells a tale of re-examination and reanalysis of specimens with a quite different interpretation. Oh, and there's a tale of the evolution of silk use by spiders!

Production and use of silk is the defining characteristic of spiders - modern advanced spiders use silk for a quite astonishing array of purposes (from taking flight to encasing eggs; from capturing prey to constructing shelters), and a single individual may produce silk of several types with distinct properties.  Spider silk is produced from specialised structures called spigots, which are in turn located on modified appendages called spinnerets (see picture on the right, from the arachnology website, where there's a description of silk production). 

In this year of not only the 200th anniversary of Charles Darwin's birth, but the 150th anniversary of the publication of The Origin of Species, we can expect the major celebratory events to be countered by the usual mediaevally-minded creationist suspects.  The journal Nature has published a useful document with the aim of highlighting an publicising why (the vast majoroty of) scientists regard evolution by natural selection as a fact -  "15 Evolutionary Gems"- the contents are as follows:

Gems from the fossil record
   1 Land-living ancestors of whales
   2 From water to land
   3 The origin of feathers
   4 The evolutionary history of teeth
   5 The origin of the vertebrate skeleton
Gems from habitats
   6 Natural selection in speciation
   7 Natural selection in lizards
   8 A case of co-evolution
   9 Differential dispersal in wild birds
  10 Selective survival in wild guppies
  11 Evolutionary history matters
Gems from molecular processes
  12 Darwin's Galapagos finches
  13 Microevolution meets macroevolution
  14 Toxin resistance in snakes and clams
  15 Variation versus stability 

The Natural History Museum has a packed programme of events to celebrate the big Darwin anniversary in 2009.   I'm not sure why they've chosen the image on the left as par tof the logo - it seems to suggest Darwin is swearing us to secrecy!  (I wonder if it's a photoshopped image...).  In any event, this is a big deal in public understanding of science, and my university, The Open University, is a significant contributor:

The Open University is working with the BBC to co-produce four TV series that consider the impact and legacy of Darwin's theories and ideas in an attempt to engage the public to take their interest in Darwin further. The four series are: Tree of Life (BBC ONE) where Sir David Attenborough argues the case for the importance of the science of evolution; Life (BBC ONE) which will capture the most extraordinary and awe-inspiring animal survival behaviours ever shown on TV; Andrew Marr on Darwin's Legacy (working title, BBC TWO) which will explore the impact of Darwin's theory in science, society, political movement and religion; and A Year in Darwin's Garden (working title, BBC TWO) in which entomologist and farmer, Jimmy Doherty, recreates many of Darwin's ground-breaking experiments with plants.

Once again, I find myself interested in a paper about the analysis of a fossil! This time the point of interest is origin of the tetrapod limb digits. The origins of the proximal elements of the tetrapod limb are well understood, and can be seen as homologues of elements of the fins of sarcopterygian (lobe-finned fish). The origins of the digits may have been fin rays, or possibly evolutionary novelties. The latter explanation was supported by developmental genetic studies and analysis of fossils (including the subject of this paper, the transitional fish/tetrapod Panderichthys). In this paper, CT scanning was used to generate 3D images of Panderichthys limbs, demonstrating the presence of distal radials, and correcting a mistaken reconstruction.
The figure below shows the skeletal structure of the limb, coloured to show homologies to the elements of the tetrapod limb. 

The latest publication from our project investigating a Drosophila homologue of WRN exonuclease is now online.  

Ivan Boubriak, Penelope A. Mason, David J. Clancy, Joel Dockray, Robert D. C. Saunders, Lynne S. Cox (2008). DmWRNexo is a 3′–5′ exonuclease: phenotypic and biochemical characterization of mutants of the Drosophila orthologue of human WRN exonuclease Biogerontology DOI: 10.1007/s10522-008-9181-3

This interesting paper investigates whether there is a relationship between polyandry and selfish genetic elements, in the fruit fly Drosophila pseudoobscura. 

Polyandry - where females have multiple mating partners - is widespread in animals, but despite its frequency, little is known of the costs and benefits of this reproductive strategy (though this paper cites evidence that the costs of multiple mating appear to outweigh the benefits.  It is likely that the benefits lie in that polyandry gives the female a greater degree of control over paternity, via sperm competition.  There is also a possibility that selfish genetic elements may promote polyandry by correlating male fitness with sperm competition.

The BBC has this report on an interesting marine biology discovery, relevant to explaining trace fossils.  Unfortunately it's a bit vague (exemplified by its title - 'Grape' is key to fossil puzzle), and doesn't have a link to the original research paper in Current Biology. Personally, I think it looks less like a grape and more like a truffle.  The picture to the left shows a cleaned up example - the real things roll around the sea floor covered in mud.

Greg Laden's Blog - Giant Gromia (amoebas) may account for ancient sea floor tracks presents a rather more coherent account of the paper, and includes a citation.  Unfortunately my university doesn't have an online subscription to Current Biology.  Rats! Rats!

There's an interesting news article in Science, entitled Last Stand for the Body Snatcher of the Himalayas?, concerning a fungus with quite unusual habits.  The full citation can be found at the end of this article.

Cordyceps sinensis is a pretty strange fungus - it infects ghost moth caterpillars, and in doing so alters their behaviour such that when they hibernate for the winter, they orient themselves on end and near to the surface.  Over the winter, the fungus consumes the caterpillar and eventually pushes a fruiting body above ground.  In the picture below, you can see remnants of the caterpillar, from which the brown 'mushroom' protrudes (picture from wikipedia).

This recent paper caught my eye, as as some of my recent research has related to the regulation of antimicrobial defence in Drosophila.  Insects have a two ways of coping with microbial infection.  Firstly, microbes may be dealt with by circulating blood cells (haemocytes) of which there are several classes.  Haemocytes to no play any role in respiration in insects.  A second means of controlling microbes involves several peptides that kill bacteria or fungi:  these are usually expressed in response to the presence of microbes in the haemolymph.  Interestingly, this induced system has a counterpart in vertebrates.  It's generally thought that the important system in clearing pathogenic microbes in insects is the induced antimicrobial peptides.  This paper investigates the roles of both systems.

The authors have evaluated the relative use of these two mechanisms of infection control in Tenebrio molitorI, the mealworm (picture above).  Their hypothesis is that the haemocytes represent the first line of defence, with the induced response of antimicrobial peptides mopping up microbes remaining from the first round defence.  In this model, the induced antimicrobial response largely functions to eliminate suviving pathogens that may be refractory to the first line of defence.

For much of my professional career as a Drosophila geneticist I've worked with polytene chromosomes, and it's always interesting to see papers with interesting tidbits of information about their structure and function. Polytene chromosomes are those rather strange structures formed from high levels of chromosome endoreduplication (see this blog article for a detailed description). Polytene chromosomes are widespread in flies, and in Drosophila are mostly studied in the larval salivary glands where they are easy to work with: Calvin Bridges used salivary gland polytene chromosomes to construct his polytene chromosome map. In this paper, Tom Hartl and colleagues show Condensin complexes (which have a function in chromosome condensation and anaphase chromosome segregation; and in vitro can induce and trap DNA supercoiling) can cause polytene chromosome disassembly and antagonise transvection.  Their data link processes of chromosome condensation and DNA supecoiling with higher order interphase nuclear structure that impacts on gene expression.

Unlike salivary gland polytene chromosomes, those of ovarian nurse cells break down during the development of the nurse cells, at about mid-oogenesis.  In this paper, two mutant alleles of a predicted component of the condensin II complex, Cap-H2 are studied.  In flies mutant for Cap-H2, the nurse cell polytene chromosomes don't disassemble.

 Wolbachia pipientis is a rather peculiar bacterium.  It's an intracellular organism, and is found in a wide variety of tax, including nematodes, crustacea, and arachnids.  About 20% of insect species are thought to have Wolbachia.  Wolbachia has evolved a number of mechanisms to ensure transmission, which is generally maternal.  There are a number of consequences of infection with these intracellular bacteria observed in different species - including reproductive isolation between infected and uninfected strains of the mosquito Culex pipiens.  I also recall seeing a old paper (though I've long-since lost the citation) which claimes a growth advantage of infected Drosophila larvae in crowded culture, though I think this must have predated the identification of Wolbachia.

So some laboratory Drosophila strains are infected with Wolbachia, while some are not.  This can lead to artefacts in many experiments.  For example, in my own lab, we had some perplexing results concerning the effects of particular transgene on viability of some combinations - the involvement of Wolbachia became clear firstly when we noticed the effects depended on which which strain was paternal and which maternal in the cross, and finally the observation that  this effect vanished after treating the transgenic stocks with antibiotic.  These kind of artefacts are particularly important to consider when working with complex characteristics such as lifespan (as we do in my lab).

A pair of recent issues of Science plonked into my mail box this week.  Among the items that caught my eyes was an exciting brief communication in Science shows a rare example of what appears to be fossil evidence of behaviour. These are Waptia-like arthropods from the Lower Cambrian, which appear to have been preserved while engaged in some form of processionary behaviour. Unlike known present day processionary arthropods, these chains of individuals appear to be physically linked - you can see in the figure that there is overlap between an individual's carapace and the preceding individual's telson. The authors propose the chains reflect migratory behaviour rather than feeding or reproduction.

In the 1950s, Louis Miller conducted a number of experiments that tried to model the origin of organic compounds in a  prebiotic world.  Among these was the Miller-Urey experiment, in which a vessel containing water, methane, ammonia and hydrogen was heated and subjected to electrical discharge (simulating lightning). Diagram of the experiment (Wikipedia).  At the time, Miller reported that a number of amino acids were formed.

This brief article describes the reanalysis  of stored vials containing the outcome of one of these experiments, using material found at the University of Chicago after Miller's death.  Apparently Miller had identified five amino acids and a number of unidentified compounds in some of the experiments.