Repeated adaptive radiations are evident when phenotypic divergence occurs within lineages, but this divergence into different forms is convergent when compared across lineages. Classic examples of such repeated adaptive divergence occur in island (for example, Caribbean Anolis lizards) and lake systems (for example, African cichlids). Host-parasite systems in many respects are analogous to island systems, where host species represent isolated islands for parasites whose life cycle is highly tied to that of their hosts. Thus, host-parasite systems might exhibit interesting cases of repeated adaptive divergence as seen in island and lake systems.
The feather lice of birds spend their entire life cycle on the body of the host and occupy distinct microhabitats on the host: head, wing, body and generalist. These microhabitat specialists show pronounced morphological differences corresponding to how they escape from host preening. We tested whether these different microhabitat specialists were a case of repeated adaptive divergence by constructing both morphological and molecular phylogenies for a diversity of avian feather lice, including many examples of head, wing, body and generalist forms.
Morphological and molecular based phylogenies were highly incongruent, which could be explained by rampant convergence in morphology related to microhabitat specialization on the host. In many cases lice from different microhabitat specializations, but from the same group of birds, were sister taxa.
This pattern indicates a process of repeated adaptive divergence of these parasites within host group, but convergence when comparing parasites across host groups. These results suggest that host-parasite systems might be another case in which repeated adaptive radiations could be relatively common, but potentially overlooked, because morphological convergence can obscure evolutionary relationships.
adaptive radiation; convergence; Phthiraptera; ectoparasites; phylogenetics
Verbal autopsy is a method for assessing probable causes of death from lay reporting of signs, symptoms and circumstances by family members or caregivers of a deceased person. Several methods of automated diagnoses of causes of death from standardized verbal autopsy questionnaires have been developed recently (Inter-VA, Tariff, Random Forest and King-Lu). Their performances have been assessed in a series of papers in BMC Medicine. Overall, and despite high specificity, the current strategies of automated computer diagnoses lead to relatively low sensitivity and positive predictive values, even for causes which are expected to be easily assessed by interview. Some methods have even abnormally low sensitivity for selected diseases of public health importance and could probably be improved. Ways to improve the current strategies are proposed: more detailed questionnaires; using more information on disease duration; stratifying for large groups of causes of death by age, sex and main category; using clusters of signs and symptoms rather than quantitative scores or ranking; separating indeterminate causes; imputing unknown cause with appropriate methods.
Please see related articles: http://www.biomedcentral.com/1741-7015/12/5; http://www.biomedcentral.com/1741-7015/12/19; http://www.biomedcentral.com/1741-7015/12/20; http://www.biomedcentral.com/1741-7015/12/21; http://www.biomedcentral.com/1741-7015/12/22; http://www.biomedcentral.com/1741-7015/12/23.
Cause of death; Verbal autopsy; Automated diagnosis; Health information system; Evaluation of health programs; Public health
There have been notable advances in the scientific understanding of regeneration within the past year alone, including two recently published in BMC Biology. Increasingly, progress in the regeneration field is being inspired by comparisons with stem cell biology and enabled by newly developed techniques that allow simultaneous examination of thousands of genes and proteins.
See research articles http://www.biomedcentral.com/1741-7007/7/83 and http://www.biomedcentral.com/1741-7007/8/5.
In the ubiquitin-proteasome system, a subset of ubiquitylated proteins requires the AAA+ ATPase p97 (also known as VCP or Cdc48) for extraction from membranes or protein complexes before delivery to the proteasome for degradation. Diverse ubiquitin adapters are known to link p97 to its client proteins, but two recent papers on the adapter protein UBXD7, including one by Bandau et al. in BMC Biology, suggest that rather than simply linking p97 to ubiquitylated proteins, this adapter may be essential to coordinate ubiquitylation and p97-mediated extraction of the proteasome substrate. These findings add to growing indications of richly diverse roles of adapters in p97-mediated signaling functions.
See research article: http://www.biomedcentral.com/1741-7007/10/36
An international collaborative effort has recently uncovered the genome of the zebra finch, a songbird model that has provided unique insights into an array of biological phenomena.
See research articles http://www.biomedcentral.com/1471-2164/9/131, http://www.biomedcentral.com/1471-2164/11/220/, http://www.biomedcentral.com/1471-2202/11/46/ and http://www.biomedcentral.com/1741-7007/8/28/
Understanding the spatio-temporal subversion of host cell signaling by bacterial virulence factors is key to combating infectious diseases. Following a recent study by Buntru and co-workers published in BMC Biology, we review how fluorescence (Forster) resonance energy transfer (FRET) has been applied to studying host-pathogen interactions and consider the prospects for its future application.
See research article http://www.biomedcentral.com/1741-7007/7/81.
The nuclear factor CTCF has been shown to be necessary for the maintenance of genetic imprinting at the mammalian H19/Igf2 locus. MacDonald and colleagues now report in BMC Biology that the mechanisms responsible for maintaining the imprinted state in Drosophila may be evolutionarily conserved and that CTCF may also play a critical role in this process.
See research article http://www.biomedcentral.com/1741-7007/8/105
Oestrogen exerts a robust yet imperfectly understood effect on sexual development in vertebrate embryos. New work by Pask and colleagues in BMC Biology indicates that it may interfere with male development by preventing nuclear localization of SOX9, a master regulator of the testis differentiation pathway.
See research article http://www.biomedcentral.com/1741-7007/8/113
Recent papers have demonstrated a role for Krüppel-like transcription factors 2, 4 and 5 in the control of mouse embryonic stem cell pluripotency. However, it is not clear whether each factor has a unique role or whether they are functionally redundant. A paper by Parisi and colleagues in BMC Biology now sheds light on the mechanism by which Klf5 regulates pluripotency.
See research article http://www.biomedcentral.com/1741-7007/8/128
Autophagy is an evolutionarily conserved lysosomal degradation route for soluble components of the cytosol and organelles. There is great interest in identifying compounds that modulate autophagy because they may have applications in the treatment of major diseases including cancer and neurodegenerative disease. Hundeshagen and colleagues describe this month in BMC Biology a screening assay based on flow cytometry that makes it possible to track distinct steps in the autophagic process and thereby identify novel modulators of autophagy.
See research article: http://www.biomedcentral.com/1741-7007/9/38
Contrary to the longstanding view that newts (Notophthalamus viridescens), but not axolotls (Ambystoma mexicanum), can regenerate a lens, a recent report in BMC Biology by Panagiotis Tsonis and colleagues shows axolotls indeed possess this ability during early larval stages. In contrast, they show that zebrafish never posses this ability, even as embryos. This underscores the importance of comparing regenerative ability across species and reinforces the need to consider organ regeneration in the context of evolution, development, and aging.
See research article: http://www.biomedcentral.com/1741-7007/10/103
The vertebrate nervous system is deeply divided into ‘somatic’ and ‘visceral’ subsystems that respond to external and internal stimuli, respectively. Molecular characterization of neurons in different groups of mollusks by Nomaksteinsky and colleagues, published in this issue of BMC Biology, reveals that the viscero-somatic duality is evolutionarily ancient, predating Bilateria.
See research article: http://www.biomedcentral.com/1741-7007/11/53
A large and complex outbreak of hepatitis C virus in Valencia, Spain that began 25 years ago led to the prosecution and conviction of an anesthetist who was accused of infecting hundreds of his patients. Evolutionary analyses of viral gene sequences were presented as evidence in the trial, and these are now described in detail by González-Candelas and colleagues in a paper published in BMC Biology. Their study illustrates the challenges and opportunities that arise from the use of phylogenetic inference in criminal trials concerning virus transmission.
See research article: http://www.biomedcentral.com/1741-7007/11/76
Daphnia pulex is the first crustacean to have its genome sequenced. Availability of the genome sequence will have implications for research in aquatic ecology and evolution in particular, as addressed by a series of papers published recently in BMC Evolutionary Biology and BMC Genomics.
See research articles http://www.biomedcentral.com/1471-2148/9/78, http://www.biomedcentral.com/1471-2164/10/527, http://www.biomedcentral.com/1471-2148/9/79, http://www.biomedcentral.com/1471-2164/10/175, http://www.biomedcentral.com/1471-2164/10/172, http://www.biomedcentral.com/1471-2164/10/169, http://www.biomedcentral.com/1471-2164/10/170 and http://www.biomedcentral.com/1471-2148/9/243.
This article is a response to Klütsch and Crapon de Caprona
See correspondence article http://www.biomedcentral.com/1741-7007/8/119 and our original research article http://www.biomedcentral.com/1741-7007/8/16.
This article is a response to Wang and Luo.
See correspondence article http://www.biomedcentral.com/1741-7007/10/30/ [WEBCITE] and the original research article http://www.biomedcentral.com/1741-7007/9/24 [WEBCITE].
This article is a response to Wang and Luo.
See correspondence article http://www.biomedcentral.com/1741-7007/10/30 and the original research article http://www.biomedcentral.com/1741-7007/9/24.
This article is a response to Vibranovski et al.
See correspondence article http://www.biomedcentral.com/1741-7007/10/49 and the original research article http://www.biomedcentral.com/1741-7007/9/29
We have previously reported a high propensity of testis-expressed X-linked genes to activation in meiotic cells, a similarity in global gene expression between the X chromosome and autosomes in meiotic germline, and under-representation of various types of tissue-specific genes on the X chromosome. Based on our findings and a critical review of the current literature, we believe that there is no global and severe silencing of the X chromosome in the meiotic male germline of Drosophila. The term 'meiotic sex chromosome inactivation' (MSCI) therefore seems misleading when used to describe the minor underexpression of the X chromosome in the testis of Drosophila, because this term erroneously implies a profound and widespread silencing of the X-linked genes, by analogy to the well-studied MSCI system in mammals, and therefore distracts from identification and analysis of the real mechanisms that orchestrate gene expression and evolution in this species.
In caves one repeatedly finds strikingly convergent patterns of evolution in diverse sets of organisms involving 'regressive' traits such as the loss of eyes and pigmentation. Ongoing debate centers around whether these regressive traits arise as the result of neutral evolutionary processes, or rather by natural selection of 'constructive' traits that arise at the expense of eyes and pigmentation. Recent research on cavefish points to the latter, suggesting that the 'constructive' trait vibrational attractive behavior and the reduction of eye size may share a common genetic basis.
See research article http://www.biomedcentral.com/1741-7007/10/108
Parasitic plants and their hosts have proven remarkably adept at exchanging fragments of mitochondrial DNA. Two recent studies provide important mechanistic insights into the pattern, process and consequences of horizontal gene transfer, demonstrating that genes can be transferred in large chunks and that gene conversion between foreign and native genes leads to intragenic mosaicism. A model involving duplicative horizontal gene transfer and differential gene conversion is proposed as a hitherto unrecognized source of genetic diversity.
See research article: http://www.biomedcentral.com/1741-7007/8/150
Medical student selection is an important but difficult task. Three recent papers by McManus et al. in BMC Medicine have re-examined the role of tests of attainment of learning (A’ levels, GCSEs, SQA) and of aptitude (AH5, UKCAT), but on a much larger scale than previously attempted. They conclude that A’ levels are still the best predictor of future success at medical school and beyond. However, A’ levels account for only 65% of the variance in performance that is found. Therefore, more work is needed to establish relevant assessment of the other 35%.
Please see related research articles http://www.biomedcentral.com/1741-7015/11/242, http://www.biomedcentral.com/1741-7015/11/243 and http://www.biomedcentral.com/1741-7015/11/244.
Medical School Admission; Predictors of performance; Aptitude testing
A recent article in BMC Biology illustrates the use of a systems-biology approach to integrate data across the transcriptome, proteome and metabolome of budding yeast in order to dissect the relationship between nutrient conditions and cell growth.
See research article http://jbiol.com/content/6/2/4 and http://www.biomedcentral.com/1741-7007/8/68
In a paper in BMC Biology Virk et al. show that Caenorhabditis elegans lifespan is extended in response to a diet of folate-deficient Escherichia coli. The deficiencies in folate biosynthesis were due to an aroD mutation, or treatment of E. coli with sulfa drugs, which are mimics of the folate precursor para-aminobenzoic acid. This study suggests that pharmacological manipulation of the gut microbiome folate status may be a viable approach to slow animal aging, and raises questions about folate supplementation.
See research article http://www.http://www.biomedcentral.com/1741-7007/10/67
Horizontal gene transfer (HGT) is relatively common in plant mitochondrial genomes but the mechanisms, extent and consequences of transfer remain largely unknown. Previous results indicate that parasitic plants are often involved as either transfer donors or recipients, suggesting that direct contact between parasite and host facilitates genetic transfer among plants.
In order to uncover the mechanistic details of plant-to-plant HGT, the extent and evolutionary fate of transfer was investigated between two groups: the parasitic genus Cuscuta and a small clade of Plantago species. A broad polymerase chain reaction (PCR) survey of mitochondrial genes revealed that at least three genes (atp1, atp6 and matR) were recently transferred from Cuscuta to Plantago. Quantitative PCR assays show that these three genes have a mitochondrial location in the one species line of Plantago examined. Patterns of sequence evolution suggest that these foreign genes degraded into pseudogenes shortly after transfer and reverse transcription (RT)-PCR analyses demonstrate that none are detectably transcribed. Three cases of gene conversion were detected between native and foreign copies of the atp1 gene. The identical phylogenetic distribution of the three foreign genes within Plantago and the retention of cytidines at ancestral positions of RNA editing indicate that these genes were probably acquired via a single, DNA-mediated transfer event. However, samplings of multiple individuals from two of the three species in the recipient Plantago clade revealed complex and perplexing phylogenetic discrepancies and patterns of sequence divergence for all three of the foreign genes.
This study reports the best evidence to date that multiple mitochondrial genes can be transferred via a single HGT event and that transfer occurred via a strictly DNA-level intermediate. The discovery of gene conversion between co-resident foreign and native mitochondrial copies suggests that transferred genes may be evolutionarily important in generating mitochondrial genetic diversity. Finally, the complex relationships within each lineage of transferred genes imply a surprisingly complicated history of these genes in Plantago subsequent to their acquisition via HGT and this history probably involves some combination of additional transfers (including intracellular transfer), gene duplication, differential loss and mutation-rate variation. Unravelling this history will probably require sequencing multiple mitochondrial and nuclear genomes from Plantago.
See Commentary: http://www.biomedcentral.com/1741-7007/8/147.
Important advances in the field of tissue engineering are arising from increased interest in novel biomaterial designs with bioactive components that directly influence cell behavior. Following the recent work of Mitchell and co-workers published in BMC Biology, we review how spatial and temporal control of signaling molecules in a matrix material regulates cellular responses for tissue-specific applications.
See research article http://www.biomedcentral.com/1741-7007/8/57