There are 28 new articles published today in PLoS ONE. You know what to do: read, rate, comment, annotate and send trackbacks! My picks for this week:
Light Variability Illuminates Niche-Partitioning among Marine Picocyanobacteria:
Phytoplankton are an important part of food webs in the ocean, and produce much of the oxygen in the Earth’s atmosphere. Due to mixing of water columns in the sea, phytoplankton have to cope with huge changes in the amount of light reaching them. In this study, Six and colleagues found that two different species of phytoplankton have widely differing capacities for tolerating sudden changes in the amount of light reaching them. These findings therefore suggest a degree of niche differentiation amongst the species of phytoplankton studied.
Canine Population Structure: Assessment and Impact of Intra-Breed Stratification on SNP-Based Association Studies:
In canine genetics, the impact of population structure on whole genome association studies is typically addressed by sampling approximately equal numbers of cases and controls from dogs of a single breed, usually from the same country or geographic area. However one way to increase the power of genetic studies is to sample individuals of the same breed but from different geographic areas, with the expectation that independent meiotic events will have shortened the presumed ancestral haplotype around the mutation differently. Little is known, however, about genetic variation among dogs of the same breed collected from different geographic regions. In this report, we address the magnitude and impact of genetic diversity among common breeds sampled in the U.S. and Europe. The breeds selected, including the Rottweiler, Bernese mountain dog, flat-coated retriever, and golden retriever, share susceptibility to a class of soft tissue cancers typified by malignant histiocytosis in the Bernese mountain dog. We genotyped 722 SNPs at four unlinked loci (between 95 and 271 per locus) on canine chromosome 1 (CFA1). We showed that each population is characterized by distinct genetic diversity that can be correlated with breed history. When the breed studied has a reduced intra-breed diversity, the combination of dogs from international locations does not increase the rate of false positives and potentially increases the power of association studies. However, over-sampling cases from one geographic location is more likely to lead to false positive results in breeds with significant genetic diversity. These data provide new guidelines for association studies using purebred dogs that take into account population structure.
A High Quality Draft Consensus Sequence of the Genome of a Heterozygous Grapevine Variety:
Viticulture takes a major scientific step forward with this publication of a high quality draft of the Pinot Noir grape genome. Riccardo Velasco and colleagues from the Grapevine Genome Initiative used shotgun sequencing to tackle the 504.6 megabase sequence, uncovering 2 million single nucleotide polymorphisms in 87% of the 29,585 identified genes, many involved in disease resistance and terpenoid synthesis. They also show that a whole genome duplication produced at least ten of the nineteen chromosomes.
A Family of Chemoreceptors in Tribolium castaneum (Tenebrionidae: Coleoptera):
Chemoperception in invertebrates is mediated by a family of G-protein-coupled receptors (GPCR). To date nothing is known about the molecular mechanisms of chemoperception in coleopteran species. Recently the genome of Tribolium castaneum was sequenced for use as a model species for the Coleoptera. Using blast searches analyses of the T. castaneum genome with previously predicted amino acid sequences of insect chemoreceptor genes, a putative chemoreceptor family consisting of 62 gustatory receptors (Grs) and 26 olfactory receptors (Ors) was identified. The receptors have seven transmembrane domains (7TMs) and all belong to the GPCR receptor family. The expression of the T. castaneum chemoreceptor genes was investigated using quantification real- time RT-PCR and in situ whole mount RT-PCR analysis in the antennae, mouth parts, and prolegs of the adults and larvae. All of the predicted TcasGrs were expressed in the labium, maxillae, and prolegs of the adults but TcasGr13, 19, 28, 47, 62, 98, and 61 were not expressed in the prolegs. The TcasOrs were localized only in the antennae and not in any of the beetles gustatory organs with one exception; the TcasOr16 (like DmelOr83b), which was localized in the antennae, labium, and prolegs of the beetles. A group of six TcasGrs that presents a lineage with the sugar receptors subfamily in Drosophila melanogaster were localized in the lacinia of the Tribolium larvae. TcasGr1, 3, and 39, presented an ortholog to CO2 receptors in D. melanogaster and Anopheles gambiae was recorded. Low expression of almost all of the predicted chemoreceptor genes was observed in the head tissues that contain the brains and suboesophageal ganglion (SOG). These findings demonstrate the identification of a chemoreceptor family in Tribolium, which is evolutionarily related to other insect species.
Visual Feedback Is Not Necessary for the Learning of Novel Dynamics:
When learning to perform a novel sensorimotor task, humans integrate multi-modal sensory feedback such as vision and proprioception in order to make the appropriate adjustments to successfully complete the task. Sensory feedback is used both during movement to control and correct the current movement, and to update the feed-forward motor command for subsequent movements. Previous work has shown that adaptation to stable dynamics is possible without visual feedback. However, it is not clear to what degree visual information during movement contributes to this learning or whether it is essential to the development of an internal model or impedance controller. We examined the effects of the removal of visual feedback during movement on the learning of both stable and unstable dynamics in comparison with the case when both vision and proprioception are available. Subjects were able to learn to make smooth movements in both types of novel dynamics after learning with or without visual feedback. By examining the endpoint stiffness and force after learning it could be shown that subjects adapted to both types of dynamics in the same way whether they were provided with visual feedback of their trajectory or not. The main effects of visual feedback were to increase the success rate of movements, slightly straighten the path, and significantly reduce variability near the end of the movement. These findings suggest that visual feedback of the hand during movement is not necessary for the adaptation to either stable or unstable novel dynamics. Instead vision appears to be used to fine-tune corrections of hand trajectory at the end of reaching movements.
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