No abstract

Mechanosensory transduction for senses such as proprioception, touch, balance, acceleration, hearing and pain relies on mechanotransduction channels, which convert mechanical stimuli into electrical signals in specialized sensory cells1. How force gates mechanotransduction channels is a central question in the field, for which there are two major models. One is the membrane-tension model: force applied to the membrane generates a change in membrane tension that is sufficient to gate the channel, as in the case of bacterial MscL channel and certain eukaryotic potassium channels2-5. The other is the tether model: force is transmitted via a tether to gate the channel. Recent study suggests that NOMPC, a mechanotransduction channel that mediates hearing and touch sensation in Drosophila, is gated by tethering of its ankyrin repeat (AR) domain to microtubules of the cytoskeleton6. Thus, a goal of studying NOMPC is to reveal the underlying mechanism of force induced gating, which could serve as a paradigm of the tether model. NOMPC, a Transient Receptor Potential (TRP) channel and the founding member of the TRPN sub-family7, fulfills all the criteria for a bona fide mechanotransduction channel1,8, and is important for a variety of mechanosensation-related behaviors such as locomotion, touch and sound sensation across different species including C. elegans9, Drosophila8,10-11 and zebrafish12. NOMPC has 29 ARs, the largest number among TRP channels. They are implicated as tether to convey force from cytoskeleton to the channel, thus to mediate mechanosensation6,13-15. A key question is how the long AR domain is organized as a tether that can trigger channel gating. Here we present a de novo atomic structure of NOMPC determined by single particle electron cryo-microscopy (cryo-EM), and discuss how its architecture could provide a means to convey mechanical force to generating an electrical signal within a cell.

Epimedium L. is a phylogenetically and economically important genus in the family Berberidaceae. We here sequenced the complete chloroplast (cp) genomes of four Epimedium species using Illumina sequencing technology via a combination of de novo and reference-guided assembly, which was also the first comprehensive cp genome analysis on Epimedium combining the cp genome sequence of E. koreanum previously reported. The five Epimedium cp genomes exhibited typical quadripartite and circular structure that was rather conserved in genomic structure and the synteny of gene order. However, these cp genomes presented obvious variations at the boundaries of the four regions because of the expansion and contraction of the inverted repeat (IR) region and the single-copy (SC) boundary regions. The trnQ-UUG duplication occurred in the five Epimedium cp genomes, which was not found in the other basal eudicotyledons. The rapidly evolving cp genome regions were detected among the five cp genomes, as well as the difference of simple sequence repeats (SSR) and repeat sequence were identified. Phylogenetic relationships among the five Epimedium species based on their cp genomes showed accordance with the updated system of the genus on the whole, but reminded that the evolutionary relationships and the divisions of the genus need further investigation applying more evidences. The availability of these cp genomes provided valuable genetic information for accurately identifying species, taxonomy and phylogenetic resolution and evolution of Epimedium, and assist in exploration and utilization of Epimedium plants.

No abstract

Ca 2ϩ -dependent activator protein for secretion (CAPS) ͉ exocytosis ͉ insulin ͉ phosphoinositides

A retrospective investigation was performed to evaluate whole-genome sequencing as a benchmark for comparing molecular subtyping methods for Salmonella enterica serotype Enteritidis and survey the population structure of commonly encountered S. enterica serotype Enteritidis outbreak isolates in the United States. A total of 52 S. enterica serotype Enteritidis isolates representing 16 major outbreaks and three sporadic cases collected between 2001 and 2012 were sequenced and subjected to subtyping by four different methods: (i) whole-genome single-nucleotide-polymorphism typing (WGST), (ii) multiple-locus variablenumber tandem-repeat (VNTR) analysis (MLVA), (iii) clustered regularly interspaced short palindromic repeats combined with multi-virulence-locus sequence typing (CRISPR-MVLST), and (iv) pulsed-field gel electrophoresis (PFGE). WGST resolved all outbreak clusters and provided useful robust phylogenetic inference results with high epidemiological correlation. While both MLVA and CRISPR-MVLST yielded higher discriminatory power than PFGE, MLVA outperformed the other methods in delineating outbreak clusters whereas CRISPR-MVLST showed the potential to trace major lineages and ecological origins of S. enterica serotype Enteritidis. Our results suggested that whole-genome sequencing makes a viable platform for the evaluation and benchmarking of molecular subtyping methods. Salmonella enterica is currently the most common bacterial foodborne pathogen in the United States, causing over 1 million cases of illnesses annually, including approximately 20,000 hospitalizations and 400 deaths (1). Serotyping is commonly used to subtype strains below the species level for epidemiologic purposes. Salmonella enterica serotype Enteritidis was the serotype most commonly linked to foodborne outbreaks between 1998 and 2008 in the United States, with shell eggs being the major vehicle for foodborne transmission (2). In recent years, S. enterica serotype Enteritidis was also found to cause multistate outbreaks associated with other foods such as ground beef (2012), Turkish pine nuts (2011), and alfalfa and spicy sprouts (2011), in addition to shelled eggs (2010) (3).During outbreak investigations, it is critical to employ subtyping methods capable of distinguishing outbreak isolates from epidemiologically distinct but genetically related bacterial strains. Most S. enterica serotype Enteritidis isolates have been shown to be genetically homogeneous, making it difficult for conventional subtyping methods such as pulsed-field gel electrophoresis (PFGE), the current gold standard for strain-level Salmonella subtyping, to discriminate between strains (4, 5). Among the S. enterica serotype Enteritidis isolates reported to PulseNet (6), approximately 45% display a single PFGE pattern using XbaI (JEGX01.0004), rendering PFGE ineffective in some foodborne outbreak investigations. One strategy to improve subtype resolution is to target hypervariable regions (i.e., regions of the bacterial chromosome with less genetic stability) in the ba...

Sequences of the full-length gene encoding the main capsid protein VP2 of 22 strains of canine parvovirus (CPV), isolated from domestic dogs in China between 1983 and 2008, were determined and analyzed in comparison with the sequences of 30 other strains of CPV from China and reference CPV isolates retrieved from GenBank. Three types of CPV, including CPV-2, CPV-2a, and CPV-2b, were detected, and CPV-2a (with 297-Ala mutation) was predominant in China. The unique Ile-324 mutation in the VP2 of Chinese CPV isolates was detected, as compared with a Tyr-324 in the VP2 of the reference CPV strains. A phylogenetic tree constructed from the VP2 genes showed that most of the Chinese strains classified in a cluster consisting of Chinese and Korean field isolates, which were distinct from Thai, U.S., and Italian isolates.

To understand the potential genetic basis of highland adaptation of fungal pathogenicity, we present here the ~116 Mb de novo assembled high-quality genome of Ophiocordyceps sinensis endemic to the Qinghai-Tibetan Plateau. Compared with other plain-dwelling fungi, we find about 3.4-fold inflation of the O. sinensis genome due to a rapid amplification of long terminal repeat retrotransposons that occurred ~38 million years ago in concert with the uplift of the plateau. We also observe massive removal of thousands of genes related to the transport process and energy metabolism. O. sinensis displays considerable lineage-specific expansion of gene families functionally enriched in the adaptability of low-temperature of cold tolerance, fungal pathogenicity and specialized host infection. We detect signals of positive selection for genes involved in peroxidase and hypoxia to enable its highland adaptation. Resequencing and analyzing 31 whole genomes of O. sinensis, representing nearly all of its geographic range, exhibits latitude-based population divergence and nature selection for population inhabitation towards higher altitudes on the Qinghai-Tibetan Plateau.