The genetic basis of individual-recognition signals in the mouse

The major histocompatibility complex (MHC) is widely assumed to be a primary determinant of individual-recognition scents in many vertebrates [1-6], but there has been no functional test of this in animals with normal levels of genetic variation. Mice have evolved another polygenic and highly polymorphic set of proteins for scent communication, the major urinary proteins (MUPs) [7-12], which may provide a more reliable identity signature ([13, 14] and A.L. Sherborne, M.D.T., S. Paterson, F.J., W.E.R.O., P. Stockley, R.J.B., and J.L.H., unpublished data). We used female preference for males that countermark competitor male scents [15-17] to test the ability of wild-derived mice to recognize individual males differing in MHC or MUP type on a variable genetic background. Differences in MHC type were not used for individual recognition. Instead, recognition depended on a difference in MUP type, regardless of other genetic differences between individuals. Recognition also required scent contact, consistent with detection of involatile components through the vomeronasal system [6, 18]. Other differences in individual scent stimulated investigation but did not result in individual recognition. Contrary to untested assumptions of a vertebrate-wide mechanism based largely on MHC variation, mice use a species-specific [12] individual identity signature that can be recognized reliably despite the complex internal and external factors that influence scents [2]. Specific signals for genetic identity recognition in other species now need to be investigated.     

The genetic basis of inbreeding avoidance in house mice

Animals might be able to use highly polymorphic genetic markers to recognize very close relatives and avoid inbreeding. The major histocompatibility complex (MHC) is thought to provide such a marker because it influences individual scent in a broad range of vertebrates. However, direct evidence is very limited. In house mice (Mus musculus domesticus), the major urinary protein (MUP) gene cluster provides another highly polymorphic scent signal of genetic identity that could underlie kin recognition. We demonstrate that wild mice breeding freely in seminatural enclosures show no avoidance of mates with the same MHC genotype when genome-wide similarity is controlled. Instead, inbreeding avoidance is fully explained by a strong deficit in successful matings between mice sharing both MUP haplotypes. Single haplotype sharing is not a good guide to the identification of full sibs, and there was no evidence of behavioral imprinting on maternal MHC or MUP haplotypes. This study, the first to examine wild animals with normal variation in MHC, MUP, and genetic background, demonstrates that mice use self-referent matching of a species-specific polymorphic signal to avoid inbreeding. Recognition of close kin as unsuitable mates might be more variable across species than a generic vertebrate-wide ability to avoid inbreeding based on MHC.     

Exonic splicing regulatory elements skew synonymous codon usage near intron-exon boundaries in mammals

In mammals there is a bias in amino acid usage near splice sites that is explained, in large part, by the high density of exonic splicing enhancers (ESEs) in these regions. Is there a similar bias for the relative use of synonymous codons, and can any such bias be predicted by their abundance in ESEs? Prior reports suggested that such trends may exist. From analysis of human exons, we find that 47 of the 59 codons with at least one synonym show differential usage in the proximity of exon ends, of which 42 remain significant after correction for multiple testing. Within sets of synonymous codons those more preferred near splice sites are generally those that are relatively more abundant within the ESEs. However, the examples given previously appear exceptionally good fits and there exist many exceptions, the usage of lysine's codons being a case in point. Similar results are observed in mouse exons. We conclude that splice regulation impacts on the choice of synonymous codons in mammals, but the magnitude of this effect is less than might at first have been supposed.     

Mandatory role of proteinase-activated receptor 1 in experimental bladder inflammation

Background  

In general, inflammation plays a role in most bladder pathologies and represents a defense reaction to injury that often times is two edged. In particular, bladder neurogenic inflammation involves the participation of mast cells and sensory nerves. Increased mast cell numbers and tryptase release represent one of the prevalent etiologic theories for interstitial cystitis and other urinary bladder inflammatory conditions. The activity of mast cell-derived tryptase as well as thrombin is significantly increased during inflammation. Those enzymes activate specific G-protein coupled proteinase-activated receptors (PAR)s.     

Metabolic Adaptations of Azospirillum brasilense to Oxygen Stress by Cell-to-Cell Clumping and Flocculation

The ability of bacteria to monitor their metabolism and adjust their behavior accordingly is critical to maintain competitiveness in the environment. The motile microaerophilic bacterium Azospirillum brasilense navigates oxygen gradients by aerotaxis in order to locate low oxygen concentrations that can support metabolism. When cells are exposed to elevated levels of oxygen in their surroundings, motile A. brasilense cells implement an alternative response to aerotaxis and form transient clumps by cell-to-cell interactions. Clumping was suggested to represent a behavior protecting motile cells from transiently elevated levels of aeration. Using the proteomics of wild-type and mutant strains affected in the extent of their clumping abilities, we show that cell-to-cell clumping represents a metabolic scavenging strategy that likely prepares the cells for further metabolic stresses. Analysis of mutants affected in carbon or nitrogen metabolism confirmed this assumption. The metabolic changes experienced as clumping progresses prime cells for flocculation, a morphological and metabolic shift of cells triggered under elevated-aeration conditions and nitrogen limitation. The analysis of various mutants during clumping and flocculation characterized an ordered set of changes in cell envelope properties accompanying the metabolic changes. These data also identify clumping and early flocculation to be behaviors compatible with the expression of nitrogen fixation genes, despite the elevated-aeration conditions. Cell-to-cell clumping may thus license diazotrophy to microaerophilic A. brasilense cells under elevated oxygen conditions and prime them for long-term survival via flocculation if metabolic stress persists.     

Can maternally inherited endosymbionts adapt to a novel host? Direct costs of Spiroplasma infection,but not vertical transmission efficiency,evolve rapidly after horizontal transfer into D. melanogaster

Maternally inherited symbionts are common in arthropods and many have important roles in host adaptation. The observation that specific symbiont lineages infect distantly related host species implies new interactions are commonly established by lateral transfer events. However, studies have shown that symbionts often perform poorly in novel hosts. We hypothesized selection on the symbiont may be sufficiently rapid that poor performance in a novel host environment is rapidly ameliorated, permitting symbiont maintenance. Here, we test this prediction for a Spiroplasma strain transinfected into the novel host Drosophila melanogaster. In the generations immediately following transinfection, the symbiont had low transmission efficiency to offspring and imposed severe fitness costs on its host. We observed that effects on host fitness evolved rapidly, being undetectable after 17 generations in the novel host, whereas vertical transmission efficiency was poorly responsive over this period. Our results suggest that long-term symbiosis may more readily be established in cases where symbionts perform poorly in just one aspect of symbiosis.     

Causes and consequences of crossing-over evidenced via a high-resolution recombinational landscape of the honey bee

BackgroundSocial hymenoptera, the honey bee (Apis mellifera) in particular, have ultra-high crossover rates and a large degree of intra-genomic variation in crossover rates. Aligned with haploid genomics of males, this makes them a potential model for examining the causes and consequences of crossing over. To address why social insects have such high crossing-over rates and the consequences of this, we constructed a high-resolution recombination atlas by sequencing 55 individuals from three colonies with an average marker density of 314 bp/marker.ResultsWe find crossing over to be especially high in proximity to genes upregulated in worker brains, but see no evidence for a coupling with immune-related functioning. We detect only a low rate of non-crossover gene conversion, contrary to current evidence. This is in striking contrast to the ultrahigh crossing-over rate, almost double that previously estimated from lower resolution data. We robustly recover the predicted intragenomic correlations between crossing over and both population level diversity and GC content, which could be best explained as indirect and direct consequences of crossing over, respectively.ConclusionsOur data are consistent with the view that diversification of worker behavior, but not immune function, is a driver of the high crossing-over rate in bees. While we see both high diversity and high GC content associated with high crossing-over rates, our estimate of the low non-crossover rate demonstrates that high non-crossover rates are not a necessary consequence of high recombination rates.

Electronic supplementary material

The online version of this article (doi:10.1186/s13059-014-0566-0) contains supplementary material, which is available to authorized users.     

Social cues of sperm competition influence accessory reproductive gland size in a promiscuous mammal

Theory predicts that males should increase overall investment in ejaculate expenditure with increasing levels of sperm competition. Since ejaculate production is costly, we may expect males to tailor their reproductive investment according to anticipated levels of sperm competition. Here, we investigate plasticity in ejaculate investment in response to cues of population average levels of sperm competition in a promiscuous mammal, the bank vole (Myodes glareolus). We manipulated the social experience of experimental subjects during sexual development via differential exposure to the odour of rival males, to simulate conditions associated with relatively high or low average levels of sperm competition. Males exposed to a high level of competition developed larger major accessory reproductive glands (seminal vesicles) than those that experienced a low level of competition, suggesting that an increased investment in the production of copulatory plugs and/or mating rate may be beneficial at relatively high sperm competition levels. However, investment in sperm production, testis size and sperm motility were not altered according to social experience. Our findings emphasize the importance of non-sperm components of the ejaculate in mammalian postcopulatory sexual selection, and add to the growing evidence linking plasticity in reproductive traits to social cues of sperm competition.     

Functional responses and scaling in predator-prey interactions of marine fishes: contemporary issues and emerging concepts

Predator-prey interactions are a primary structuring force vital to the resilience of marine communities and sustainability of the world's oceans. Human influences on marine ecosystems mediate changes in species interactions. This generality is evinced by the cascading effects of overharvesting top predators on the structure and function of marine ecosystems. It follows that ecological forecasting, ecosystem management, and marine spatial planning require a better understanding of food web relationships. Characterising and scaling predator-prey interactions for use in tactical and strategic tools (i.e. multi-species management and ecosystem models) are paramount in this effort. Here, we explore what issues are involved and must be considered to advance the use of predator-prey theory in the context of marine fisheries science. We address pertinent contemporary ecological issues including (1) the approaches and complexities of evaluating predator responses in marine systems; (2) the 'scaling up' of predator-prey interactions to the population, community, and ecosystem level; (3) the role of predator-prey theory in contemporary fisheries and ecosystem modelling approaches; and (4) directions for the future. Our intent is to point out needed research directions that will improve our understanding of predator-prey interactions in the context of the sustainable marine fisheries and ecosystem management.