Ecological constraint and the evolution of sexual dichromatism in darters

It is not known how environmental pressures and sexual selection interact to influence the evolution of extravagant male traits. Sexual and natural selection are often viewed as antagonistic forces shaping the evolution of visual signals, where conspicuousness is favored by sexual selection and crypsis is favored by natural selection. Although typically investigated independently, the interaction between natural and sexual selection remains poorly understood. Here, we investigate whether sexual dichromatism evolves stochastically, independent from, or in concert with habitat use in darters, a species‐rich lineage of North American freshwater fish. We find the evolution of sexual dichromatism is coupled to habitat use in darter species. Comparative analyses reveal that mid‐water darter lineages exhibit a narrow distribution of dichromatism trait space surrounding a low optimum, suggesting a constraint imposed on the evolution of dichromatism, potentially through predator‐mediated selection. Alternatively, the transition to benthic habitats coincides with greater variability in the levels of dichromatism that surround a higher optimum, likely due to relaxation of the predator‐mediated selection and heterogeneous microhabitat dependent selection regimes. These results suggest a complex interaction of sexual selection with potentially two mechanisms of natural selection, predation and sensory drive, that influence the evolution of diverse male nuptial coloration in darters.     

Hon-yaku: a biology-driven Bayesian methodology for identifying translation initiation sites in prokaryotes

Background  

Computational prediction methods are currently used to identify genes in prokaryote genomes. However, identification of the correct translation initiation sites remains a difficult task. Accurate translation initiation sites (TISs) are important not only for the annotation of unknown proteins but also for the prediction of operons, promoters, and small non-coding RNA genes, as this typically makes use of the intergenic distance. A further problem is that most existing methods are optimized for Escherichia coli data sets; applying these methods to newly sequenced bacterial genomes may not result in an equivalent level of accuracy.     

Intracellular effectors and modulators of GABA-A and GABA-B receptors: a commentary

The inhibitory neurotransmitter GABA activates two receptor subtypes that can be distinguished by their pharmacology. The GABA-A site is competitively antagonized by bicuculline and exclusively coupled to a chloride channel. The GABA-B receptor, for which baclofen is the only specific agonist, is resistant to bicuculline inhibition and, depending upon its localization, will activate K currents and/or inhibit Ca currents. Both electrophysiological and biochemical approaches have been applied to the study of each receptor. The membrane and intracellular components that to date have been implicated in GABA-B activation are discussed: G proteins, adenylate cyclase and intracellular calcium levels. This latter factor is also discussed with respect to GABA-A receptor action.     

Non-synonymous polymorphisms in the P2RX 4 are related to bone mineral density and osteoporosis risk in a cohort of Dutch fracture patients

In the present study we investigated whether single nucleotide polymorphisms (SNPs) in the P2RX₄, which alter the P2X₄R function, are associated with the development of osteoporosis and whether an interaction between the P2X₄R and P2X₇R confer a synergistic effect of these two receptors on osteoporosis risk. Patients with fracture (690 females and 231 males, aged ≥50 years) were genotyped for three non-synonymous P2X₄R SNPs. Bone mineral density (BMD) was measured at the total hip, lumbar spine, and femoral neck. Subject carrying the variant allele of the Tyr315Cys polymorphism showed a 2.68-fold (95 % CI, 1.20–6.02) higher risk of osteoporosis compared with wild-type subject. Furthermore, significant lower lumbar spine BMD values were observed in subjects carrying the Cys315 allele as compared with wild-type (0.85 ± 0.17 and 0.93 ± 0.17 g/cm², respectively; p < 0.001). Assuming a recessive model, carriers of the variant allele of the Ser242Gly polymorphism showed increased BMD values at the lumbar spine compare to wild-type subject (1.11 ± 0.35 and 0.92 ± 0.17 g/cm², respectively; p = 0.0045). This is the first study demonstrating an association of non-synonymous polymorphisms in the P2RX₄ and the risk of osteoporosis, suggesting a role of the P2X₄R in the regulation of bone mass.

Electronic supplementary material

The online version of this article (doi:10.1007/s11302-012-9337-0) contains supplementary material, which is available to authorized users.