SruI restriction endonuclease from Selenomonas ruminantium

Abstract Sru I, specific restriction endonuclease, has been characterized from Selenomonas ruminantium isolated from the rumen of fallow deer. Results from the study demonstrate that S. ruminantium 18D possesses a type II restriction endonuclease, which recognizes the sequence 5'-TTT↓AAA-3'. The recognition sequence of Sru I was identified using digestions on pBR322, pBR328, pUC18, M13mp18RF, pACYC184 and λDNA. The cleavage patterns obtained were compared with computer-derived data. Sru I recognises the palindromic hexanucleotide sequence and cleaves DNA after the third T in the sequence, producing blunt ends. The purification and characterization of restriction endonuclease Sru I presented here is the first described for Selenomonas ruminantium spp. and demonstrates that this microorganism pocesses a DNA-cleaving enzyme with the same specificity as Dra I or Aha III.     

Songs of Holcostethus strictus (Fabricius): a different repertoire among landbugs (Heteroptera: Pentatomidae)

Songs emitted during mating by male and female Holcostethus strictus were recorded as substrate vibrations. Spectra of the vibrational signals have a dominant frequency peak between 100 and 260 Hz and in this respect reflect the general characteristic of the family Pentatomidae. Songs of H. strictus differ from the song repertoire of the southern green stink bug Nezara viridula (L.) (Pentatomidae) in many respects. The female calling and courtship songs differ in echeme and phrase duration. The male calling song is composed of spectrally different subunits. The male courtship song is characterised by three types of spectrally and temporally different echemes. The male copulatory song is composed of echemes of two types, which constitute a phrase of less regular temporal structure. In H. strictus, males start to sing first and female songs are less complex than in N. viridula. The female calling song is evoked by male calling and does not trigger male response. The female and male courtship song phrases are superimposed on one another and we have not observed any obvious regularity in their exchange. The possible role of different songs in H. strictus is discussed and compared with that in other pentatomide landbug species.     

Stink bug interaction with host plants during communication

In solitary plant-dwelling stink bug species, success depends crucially on efficient mate location and recognition, mediated by signals transmitted through the plant. All stink bugs investigated so far communicate with species and sex-specific narrow-band calling and courtship song signals produced by abdomen vibration. Calling songs of lower specificity are characterized by readily repeated units emitted with regular repetition rate from the same place on a plant, while courtship songs take place at shorter distances in the process of species and sex recognition, together with signals of other modalities. Signal spectra with about 100Hz fundamental frequency and harmonics below 1000Hz are tuned to the resonant properties of their green host plants. The majority of the identified leg vibratory receptor cells and the underlying ventral cord interneurons respond best in the frequency range below 500Hz. Green plants with low pass filtering properties transmit optimally signals with a dominant frequency around 100Hz and strongly attenuate vibrations above 600Hz. Accurate tuning of signal spectral properties with the plant's mechanical characteristics enables communication over several meter distances, with dispersive bending waves running through the plant's rod-like structures under standing wave conditions.     

Disruption of the reproductive behaviour of Scaphoideus titanus by playback of vibrational signals

Scaphoideus titanus Ball (Hemiptera: Cicadellidae: Deltocephalinae) is the vector of the grapevine disease Flavescence dorée. In S. titanus the male–female duet (MFD), based on species-specific vibrational signals, is essential for successful copulation. The female reply within a duet is a single pulse that is coupled with the male pulse with constant latency. It has been shown that a rival male can interrupt an existing duet by emitting disruptive noise signals. We tested whether the reproductive behaviour of S. titanus can be disrupted by the playback of intra-specific and synthesized vibrational signals. Tested males responded to the playback of an MFD with typical rivalry behaviour. Such behaviour includes silent search for a duetting female (satellite behaviour) and/or emission of disruptive signals. These signals were emitted either after exchange of male–female pulses or after two male pulses coupled by latency corresponding to the female response window. The onset of male disruptive signals overlapped with a female pulse. We suggest that the intruder's disruptive signals can mask the female reply and confuse courting males. Playback of disruptive vibrational signals reduced the level of male calling and interrupted an established MFD that consequently resulted in a significantly reduced number of copulations. These results indicate that the vibrational communication channel is open to interference either from abiotic environmental noise or from signals produced by sexual competitors or heterospecifics. The present study also suggests that a detailed understanding of leafhopper behaviour is essential for trying new approaches in the development of more environmentally friendly control practices.     

Basidiomycete Clitocybe nebularis is rich in lectins with insecticidal activities

Basidiomycete mushrooms are a rich source of unique substances, including lectins, that could potentially be useful in biotechnology or biomedical applications. Lectins are a group of carbohydrate-binding proteins with diverse biological activities and functions. Here, we demonstrate the presence of a number of lectins in the basidiomycete mushroom Clitocybe nebularis. Glucose-, galactose-, sucrose-, lactose-, and Sepharose-binding lectins were isolated from fruiting bodies using affinity chromatography on Sepharose-immobilized sugars or on Sepharose. The lectins were characterized biochemically and their binding specificities examined by agglutination and agglutination inhibition assays. In addition, insecticidal and anti-nutritional properties of the lectins were studied against a model organism, fruit fly (Drosophila melanogaster), and Colorado potato beetle (Leptinotarsa decemlineata). Of the several basidiomycete mushrooms screened, C. nebularis extract showed the most potent insecticidal activity. Sucrose-binding lectin showed the strongest activity against D. melanogaster, followed by lactose- and galactose-binding lectins. Feeding bioassays with Colorado potato beetle revealed that C. nebularis extract exhibited high anti-nutritional activity against the insect; and of those tested, only lactose-binding lectin, named CNL showed the effect. Mushroom C. nebularis is shown to be rich in a variety of lectins with versatile biological activities, including insecticidal and anti-nutritional effects. C. nebularis lectins could thus have potential for use as natural insecticides.     

Transition along gradient from warm to mesic temperate forests evaluated by GAMM

Aims The aim of the study was to discover what set of variables best explains the transition from warm to mesic forest vegetation. Based on various variables grouped into sets (geomorphological, ecological, structural, soil characteristics and chorological), six models were built and tested by generalized additive mixed models (GAMMs). We assumed that each set of variables has different explanatory power. Our aim was to compare the six different models (sets of variables), to test which model best explains the species turnover in forest communities along the transition between warm and mesic temperate forests and to try to find reasons for the different explanatory power of the models.Methods The research took place in the southern part of the Balkan Peninsula. Field sampling was done according to standard methods. The gradient from warm to mesic forests was defined as the turnover of species and evaluated by projection of samples on the first unconstrained DCA axis. Geomorphological, ecological, structural and soil characteristics, together with chorological sets of variables, were regressed on the turnover of species composition. Based on the five sets of variables, six models were constructed and tested by generalized additive mixed models.Important findings Ecological conditions best explain the change of forest communities along the gradient; evolution and the development of vegetation reflected in chorotypes are also of high importance; geomorphology and structure seem not to change so dramatically and soil shows the least significant differences of all. Ecological variables are the most important set of variables in the transition between warm and mesic temperate forests but eco-evolutionary dynamics after the Pleistocene should also be taken into consideration.     

Glycosphingolipid Requirements for Endosome-to-Golgi Transport of Shiga Toxin

Shiga toxin binds to globotriaosylceramide (Gb3) receptors on the target cell surface. To enter the cytosol, Shiga toxin is dependent on endocytic uptake, retrograde transport to the Golgi apparatus and further to the endoplasmic reticulum before translocation of the enzymatically active moiety to the cytosol. Here, we have investigated the importance of newly synthesized glycosphingolipids for the uptake and intracellular transport of Shiga toxin in HEp-2 cells. Inhibition of glycosphingolipid synthesis by treatment with either PDMP or Fumonisin B₁ for 24–48 h strongly reduced the transport of Gb3-bound Shiga toxin from endosomes to the Golgi apparatus. This was associated with a change in localization of sorting nexins 1 and 2, and accompanied by a protection against the toxin. In contrast, there was no effect on transport or toxicity of the plant toxin ricin. High-resolution mass spectrometry revealed a 2-fold reduction in Gb3 at conditions giving a 10-fold inhibition of Shiga toxin transport to the Golgi. Furthermore, mass spectrometry showed that the treatment with PDMP (DL-threo-1-phenyl-2-decanoylamino-3-morpholino-1-propanol) and Fumonisin B₁ among other changes of the lipidome, affected the relative content of the different glycosphingolipid species. The largest depletion was observed for the hexosylceramide species with the N -amidated fatty acid 16:0, whereas hexosylceramide species with 24:1 were less affected. Quantitative lipid profiling with mass spectrometry demonstrated that PDMP did not influence the content of sphingomyelins, phospholipids and plasmalogens. In contrast, Fumonisin B₁ affected the amount and composition of sphingomyelin and glycolipids and altered the profiles of phospholipids and plasmalogens.     

Do chemical signals mediate reproductive behavior of Trupanea vicina,an emerging pest of ornamental marigold production in California?

A variety of signals mediate reproductive behaviors of Tephritidae, and studies of such behaviors have focused predominantly on economically important tephritid pest species. Trupanea vicina (Wulp) (Diptera: Tephritidae: Tephritinae), an Asteraceae‐feeding fruit fly, was not considered a pest until recently, when large populations developed on marigolds in California (USA) nurseries. Understanding courtship behavior and the signals that mediate mating behavior in T. vicina could produce leads for new methods of controlling this emerging pest species. Most of the sexual behaviors observed in T. vicina were expressed by males and reflected the general characteristics of known reproductive behaviors in the genus Trupanea. Analyses of headspace volatiles indicated the presence of almost exclusively one male‐specific compound, 1‐nonanol. Age‐related changes were observed in the amount but not in the composition of the male‐produced volatiles. Aerations of males showed no diel periodicity in 1‐nonanol production, but an increase after mating. Solid‐phase microextraction wipe samples from various body parts of male T. vicina showed that 1‐nonanol was concentrated on the abdomens of males exhibiting pleural distension. Laboratory bioassays failed to detect any strong attraction of either sex to synthetic 1‐nonanol. Although the functional role of 1‐nonanol in T. vicina's biology is not yet clear, we suggest that it must have some role in the life history of this species, given the relatively large amounts in which it is produced, and the specialized structures used in its production and release. Analysis of cuticular hydrocarbons extracted from males and females showed pronounced sexual dimorphism in the cuticular lipid profiles, suggesting that these compounds may have a role as short‐range and contact pheromones.     

Directional sensitivity of wind-sensitive giant interneurons in the cave cricket Troglophilus neglectus.

Unlike the situation in most cockroach and cricket species studied so far, the wind-sensitive cerci of the cave cricket Troglophilus neglectus Krauss (Rhaphidophoridae, Orthoptera) are not oriented parallel to the body axis but perpendicular to it. The effects of this difference on the morphology, and directional sensitivity of cercal giant interneurons (GIs), were investigated. In order to test the hypothesis that the 90 degrees change in cercal orientation causes a corresponding shift in directional sensitivity of GIs, their responses in both the horizontal and vertical planes were tested. One ventral and four dorsal GIs (corresponding to GIs 9-1a and 9-2a, 9-3a, 10-2a, 10-3a of gryllid crickets) were identified. The ventral GI 9-1a of Troglophilus differed somewhat from its cricket homologue in its dendritic arborisation and its directional sensitivity in the horizontal plane. The morphology and horizontal directionality of the dorsal GIs closely resembled that of their counterparts in gryllids. In the vertical plane, the directionality of all GIs tested was similar. They were all excited mainly by wind puffs from the axon-ipsilateral quadrant. The results suggest that directional sensitivity to air currents in the horizontal plane is maintained despite the altered orientation of the cerci. This is presumably due to compensatory modifications in the directional pReferences of the filiform hairs.     

Divergent apparent temperature sensitivity of terrestrial ecosystem respiration

Aims Recent studies revealed convergent temperature sensitivity of ecosystem respiration (R e) within aquatic ecosystems and between terrestrial and aquatic ecosystems. We do not know yet whether various terrestrial ecosystems have consistent or divergent temperature sensitivity. Here, we synthesized 163 eddy covariance flux sites across the world and examined the global variation of the apparent activation energy (Ea), which characterizes the apparent temperature sensitivity of and its interannual variability (IAV) as well as their controlling factors.Methods We used carbon fluxes and meteorological data across FLUXNET sites to calculate mean annual temperature, temperature range, precipitation, global radiation, potential radiation, gross primary productivity and R e by averaging the daily values over the years in each site. Furthermore, we analyzed the sites with>8 years data to examine the IAV of Ea and calculated the standard deviation of Ea across years at each site to characterize IAV.Important findings The results showed a widely global variation of Ea, with significantly lower values in the tropical and subtropical areas than in temperate and boreal areas, and significantly higher values in grasslands and wetlands than that in deciduous broadleaf forests and evergreen forests. Globally, spatial variations of Ea were explained by changes in temperature and an index of water availability with differing contribution of each explaining variable among climate zones and biomes. IAV and the corresponding coefficient of variation of Ea decreased with increasing latitude, but increased with radiation and corresponding mean annual temperature. The revealed patterns in the spatial and temporal variations of Ea and its controlling factors indicate divergent temperature sensitivity of R e, which could help to improve our predictive understanding of R e in response to climate change.