A Centipede Toxin Family Defines an Ancient Class of CSαβ Defensins

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Population biology of a selfish sex ratio distorting element in a booklouse (Psocodea: Liposcelis)

Arthropods harbour a variety of selfish genetic elements that manipulate reproduction to be preferentially transmitted to future generations. A major ongoing question is to understand how these elements persist in nature. In this study, we examine the population dynamics of an unusual selfish sex ratio distorter in a recently discovered species of booklouse, Liposcelis sp. (Psocodea: Liposcelididae) to gain a better understanding of some of the factors that may affect the persistence of this element. Females that carry the selfish genetic element only ever produce daughters, although they are obligately sexual. These females also only transmit the maternal half of their genome. We performed a replicated population cage experiment, varying the initial frequency of females that harbour the selfish element, and following female frequencies for 20 months. The selfish genetic element persisted in all cages, often reaching very high (and thus severely female‐biased) frequencies. Surprisingly, we also found that females that carry the selfish genetic element had much lower fitness than their nondistorter counterparts, with lower lifetime fecundity, slower development and a shorter egg‐laying period. We suggest that differential fitness plays a role in the maintenance of the selfish genetic element in this species. We believe that the genetic system in this species, paternal genome elimination, which allows maternal control of offspring sex ratio, may also be important in the persistence of the selfish genetic element, highlighting the need to consider species with diverse ecologies and genetic systems when investigating the effects of sex ratio manipulators on host populations.     

Identification of Peptides Implicated in Antibacterial Activity of Snow Crab Hepatopancreas Hydrolysates by a Bioassay-Guided Fractionation Approach Combined with Mass Spectrometry

Snow crab (Chionoecetes opilio) by-products are a rich source of biomolecules, such as lipids, proteins, and chitin, which have not been extensively investigated. This study aims to identify antibacterial peptides to enhance the value of C. opilio by-products. After hydrolysis of different component parts using Protamex®, and concentration by solid-phase extraction, the resulting fractions were tested for antibacterial activity against Escherichia coli, Listeria innocua, and Vibrio parahaemolyticus. Hepatopancreas was the only tissue to display antibacterial activity detected using this protocol. Four fractions obtained with and without enzymatic hydrolysis of hepatopancreas followed by SPE C18 fractionation and elution with 50 and 80% acetonitrile demonstrated bacteriostatic activity against L. innocua HPB13, from concentrations of 0.30 to 43.05 mg/mL of peptides/proteins. Eleven peptides sharing at least 80% amino acid homology with four antimicrobial peptides were identified by mass spectrometry. Two peptides had homology to crustin-like and yellowfin tuna GAPDH antimicrobial peptides belonging to the marine organisms Penaeus monodon and Thunnus albacares, respectively. Other peptide sequence homologies were also identified: Odorranain-C7 from the frog Odorrana grahami and a predicted antibacterial peptide in the Asian ladybeetle Harmonia axyridis. These active peptides may represent a novel group of bioactive peptides deserving further investigation as food preservatives.

     

Pesticide exposure affects flight dynamics and reduces flight endurance in bumblebees

The emergence of agricultural land use change creates a number of challenges that insect pollinators, such as eusocial bees, must overcome. Resultant fragmentation and loss of suitable foraging habitats, combined with pesticide exposure, may increase demands on foraging, specifically the ability to collect or reach sufficient resources under such stress. Understanding effects that pesticides have on flight performance is therefore vital if we are to assess colony success in these changing landscapes. Neonicotinoids are one of the most widely used classes of pesticide across the globe, and exposure to bees has been associated with reduced foraging efficiency and homing ability. One explanation for these effects could be that elements of flight are being affected, but apart from a couple of studies on the honeybee (Apis mellifera), this has scarcely been tested. Here, we used flight mills to investigate how exposure to a field realistic (10 ppb) acute dose of imidacloprid affected flight performance of a wild insect pollinator—the bumblebee, Bombus terrestris audax. Intriguingly, observations showed exposed workers flew at a significantly higher velocity over the first ¾ km of flight. This apparent hyperactivity, however, may have a cost because exposed workers showed reduced flight distance and duration to around a third of what control workers were capable of achieving. Given that bumblebees are central place foragers, impairment to flight endurance could translate to a decline in potential forage area, decreasing the abundance, diversity, and nutritional quality of available food, while potentially diminishing pollination service capabilities.     

Carbanilation of cereal beta-glucans for molecular weight determination and conformational studies

Cereal beta-glucans can form aggregates in aqueous solution. The presence of aggregates in cereal beta-glucan solutions led to inaccurate determination of molecular weights and it was believed that intermolecular hydrogen bonding caused the aggregation. To eliminate aggregates, a carbanilation method for molecular weight determination of cereal beta-glucans was developed. Wheat beta-glucan samples were selected for investigation. The carbanilation method can prevent intermolecular hydrogen bonding by blocking hydroxyl groups with phenyl carbamate groups. The carbanilates of cereal beta-glucans were prepared by the reaction of cereal beta-glucans with phenylisocyanate catalyzed by DMSO and pyridine. To avoid degradation during the carbanilation reaction, relatively mild conditions were used, which led to incomplete substitution (DS: approximately 2). However, after the carbanilation reaction, the carbanilates dissolved completely in 1,4-dioxane solution without any detectable aggregates, which allowed accurate molecular weight determination. The degree of substitution (DS) of carbanilates was determined by both a nitrogen content method and an FT-IR method. The FT-IR method proved to be the more effective for DS estimation. Using this method, the converted molecular weights of cereal beta-glucans were in good agreement with the results measured in 0.5M NaOH solution, which previously was shown to be a good solvent for cereal beta-glucans. After the carbanilation reaction, conformational changes of carbanilates were studied by static and dynamic light scattering techniques. The fractal dimension (d(f)=2.27) and the structure sensitive parameters (rho >2) suggested a porous globular structure for partially carbanilated beta-glucans.     

A protocol for isolation and visualization of yeast nuclei by scanning electron microscopy (SEM)

This protocol details methods for the isolation of yeast nuclei from budding yeast (Saccharomyces cerevisiae) and fission yeast (Schizosaccharomyces pombe), immuno-gold labeling of proteins and visualization by field emission scanning electron microscopy (FESEM). This involves the removal of the yeast cell wall and isolation of the nucleus from within, followed by subsequent processing for high-resolution microscopy. The nuclear isolation step can be performed in two ways: enzymatic treatment of yeast cells to rupture the cell wall and generate spheroplasts (cells that have partially lost their cell wall and their characteristic shape), followed by isolation of the nuclei by centrifugation or homogenization; and whole cell freezing followed by manual cell rupture and centrifugation. This protocol has been optimized for the visualization of the yeast nuclear envelope (NE), nuclear pore complexes (NPCs) and associated cyto-skeletal structures. Samples once processed for FESEM can be stored under vacuum for weeks, allowing considerable time for image acquisition.     

Oxylipin Pathway in Rice and Arabidopsis

Plants have evolved complex signaling pathways to coordinate responses to developmental and environmental Information. The oxylipin pathway Is one pivotal lipid-based signaling network, composed of several competing branch pathways, that determines the plant＇s ability to adapt to various stimuli. Activation of the oxyllpln pathway Induces the de novo synthesis of biologically active metabolltes called ＂oxyllplns＂. The relative levels of these metabolltes are a distinct indicator of each plant species and determine the ability of plants to adapt to different stimuli. The two major branches of the oxyllpln pathway, allene oxide synthase （AOS） and hydroperoxlde lyase （HPL） are responsible for production of the signaling compounds, jasmonates and aldehydes respectively. Here, we compare and contrast the regulation of AOS and HPL branch pathways In rice and Arabidopsis as model monocotyledonous and dicotyledonous systems. These analyses provide new Insights Into the evolution of JAs and aldehydes signaling pathways, and the complex network of processes responsible for stress adaptations In monocots and dicots.     

Characterization of <Emphasis Type="Italic">target</Emphasis> nuclear DNA from faeces reduces technical issues associated with the assumptions of low-quality and quantity template

Faecal material has increasingly become an important non-invasive source of DNA for wildlife population genetics. However, DNA from faecal sources can have issues associated with quantity (low-template and/or low target-to-total DNA ratio) and quality (degradation and/or low DNA-to-inhibitor ratio). A number of studies utilizing faecal material assume and compensate for the above properties with minimal characterization of quantity or quality of target DNA, which can unnecessarily increase the risk of downstream technical problems. Here, we present a protocol which quantifies faecal DNA using a two step approach: (1) estimating total DNA concentration using a Picogreen^TM fluorescence assay and (2) estimating target nuclear DNA concentration by comparing amplification products of field samples at suspected concentrations to those of control DNA at known concentrations. We applied this protocol to faecal material collected in the field from two species: woodland caribou (Rangifer tarandus) and swift fox (Vulpes velox). Total DNA estimates ranged from 6.5 ng/μl to 28.6 ng/μl (X = 16.2 ng/μl) for the caribou extracts and 1.0–26.1 ng/μl (X = 7.5 ng/μl) for the swift fox extracts. Our results showed high concordance between total and target DNA estimates from woodland caribou faecal extracts, with only 10% of the samples showing relatively lower target-to-total DNA ratios. In contrast, DNA extracts from swift fox scat exhibited low target DNA yields, with only 38% (19 of 50) of the samples showing comparative target DNA amplification of at least 0.1 ng. With this information, we were able to estimate the amount of target DNA entered into PCR amplifications, and identify samples having target DNA below a lower threshold of 0.2 ng and requiring modification to genotyping protocols such as multiple tube amplification. Our results here also show that this approach can easily be adapted to other species where faeces are the primary source of DNA template.