Experimentell bewirkte Blockierung der histologischen Differenzierung in der Chorda von Triton

Ohne ZusammenfassungAusgeführt mit Unterstützung der Stiftung für wissenschaftliche Forschung an der Universität Zürich.     

Bayesian Weighing of Electron Cryo-Microscopy Data for Integrative Structural Modeling

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Three-dimensional preparation and imaging reveal intrinsic microtubule properties

We present an experimental investigation of microtubule dynamic instability in three dimensions, based on laser light-sheet fluorescence microscopy. We introduce three-dimensional (3D) preparation of Xenopus laevis egg extracts in Teflon-based cylinders and provide algorithms for 3D image processing. Our approach gives experimental access to the intrinsic dynamic properties of microtubules and to microtubule population statistics in single asters. We obtain evidence for a stochastic nature of microtubule pausing.     

Metazoan parasite assemblages of wild Seriola lalandi (Carangidae) from eastern and southern Australia

Yellowtail kingfish, Seriola lalandi support significant commercial and recreational fisheries as well as aquaculture operations throughout the world. Metazoan parasite infections of S. lalandi are of considerable economic and ecological importance, yet very little is known about wild parasite assemblages. S. lalandi were collected from the east coast and south coast of Australia and examined for metazoan parasites. Forty-three parasite taxa were identified, including 26 new host records. Four of the parasite species recovered have been previously associated with disease or mortality in Seriola aquaculture. Comparisons are made between ectoparasite and endoparasite prevalence and intensity of S. lalandi from New South Wales and Victoria. S. lalandi sampled from the east coast of Australia shared ectoparasites previously documented from this species in New Zealand, providing support that S. lalandi in the Tasman Sea comprise a single stock. Based on previously used criteria to evaluate the suitability of parasites as biological tags, the monogenean Paramicrocotyloides reticularis Rohde and the copepod Parabrachiella seriolae Yamaguti and Yamasu may be potentially useful for stock discrimination.     

Structure-function mapping of a heptameric module in the nuclear pore complex

The nuclear pore complex (NPC) is a multiprotein assembly that serves as the sole mediator of nucleocytoplasmic exchange in eukaryotic cells. In this paper, we use an integrative approach to determine the structure of an essential component of the yeast NPC, the ~600-kD heptameric Nup84 complex, to a precision of ~1.5 nm. The configuration of the subunit structures was determined by satisfaction of spatial restraints derived from a diverse set of negative-stain electron microscopy and protein domain-mapping data. Phenotypic data were mapped onto the complex, allowing us to identify regions that stabilize the NPC's interaction with the nuclear envelope membrane and connect the complex to the rest of the NPC. Our data allow us to suggest how the Nup84 complex is assembled into the NPC and propose a scenario for the evolution of the Nup84 complex through a series of gene duplication and loss events. This work demonstrates that integrative approaches based on low-resolution data of sufficient quality can generate functionally informative structures at intermediate resolution.     

Duetting Behaviour in the Leafhopper Aphrodes makarovi (Hemiptera: Cicadellidae)

Mate recognition and location in Cicadellidae is mediated exclusively via substrate-borne vibrational signals. In the present study we investigated vibrational signals and mate searching behaviour of the leafhopper Aphrodes makarovi. We studied mating behaviour and exchange of vibrational signals between live insects and in playback experiments. Males emitted long and complex calling signals composed of several sections. Female reply was long and always overlapped the end of the male call. The exchange of male and female vibrational signals was a complex and dynamic interaction during which both partners modified their signals according to partner’s reply. The duration of female reply was influenced by the duration of the male call to which she was responding, while the duration of male call was influenced by the duration of the previous female reply. Such relationship suggests the role of sexual selection in the evolution of male vibrational signals.