The zebra mussel (<Emphasis Type="Italic">Dreissena polymorpha</Emphasis>) impacts European bitterling (<Emphasis Type="Italic">Rhodeus amarus</Emphasis>) load in a host freshwater mussel (<Emphasis Type="Italic">Unio pictorum</Emphasis>)

The European bitterling, Rhodeus amarus, is a non-indigenous fish species in British fresh waters. It lays its eggs in unionid mussels which themselves are vulnerable to fouling by the non-indigenous zebra mussel, Dreissena polymorpha. Observations from an unmanipulated natural system showed that only 27% of zebra mussel-fouled Unio pictorum hosted bitterling, while 47% of unfouled U. pictorum hosted bitterling. We conducted a field experiment in the River Great Ouse catchment, Cambridgeshire, England in May–June 2007 and 2008 to quantify the impact of zebra mussels on bitterling load in host mussels. Zebra mussel-fouled unionids were significantly less likely to host bitterling than unfouled unionids. The number of unionids hosting bitterling did not differ significantly whether the zebra mussels fouling the unionid were alive or dead. Bitterling appeared to discriminate against zebra mussel-fouled unionids less as the 2007 breeding season advanced, potentially because preferred unfouled unionids had a higher bitterling load, and were therefore relatively lower quality hosts than at the start of the breeding season.     

Experimental ‘omics’ data in tree research: facing complexity

High-throughput experimental technology has provided insight into the inner functioning of plants. The current experimental technology facilitates the study of plant systems in a holistic manner, measuring observables from the genome, proteome, and metabolome up to the level of the ecosystem. The call for a systemic view in plant research is being made from multiple research fields. Although not yet fully developed for tree research, data sources are also rapidly growing in this area. Nevertheless, there are challenges and pitfalls in dealing with such increases in data. Some of these difficulties are deeply rooted in the complexity of the evolutionary systems. The lessons from complexity theory are rooted in studies performed several decades ago. Honouring principles that were formulated before bioinformatics and systems biology had been introduced facilitates the derivation of analytical methods with the potential to overcome these challenges in several ways.     

Conserved dimeric subunit stoichiometry of SLC26 multifunctional anion exchangers

The SLC26 gene family encodes multifunctional transport proteins in numerous tissues and organs. Some paralogs function as anion exchangers, others as anion channels, and one, prestin (SLC26A5), represents a membrane-bound motor protein in outer hair cells of the inner ear. At present, little is known about the molecular basis of this functional diversity. We studied the subunit stoichiometry of one bacterial, one teleost, and two mammalian SLC26 isoforms expressed in Xenopus laevis oocytes or in mammalian cells using blue native PAGE and chemical cross-linking. All tested SLC26s are assembled as dimers composed of two identical subunits. Co-expression of two mutant prestins with distinct voltage-dependent capacitances results in motor proteins with novel electrical properties, indicating that the two subunits do not function independently. Our results indicate that an evolutionarily conserved dimeric quaternary structure represents the native and functional state of SLC26 transporters.     

Dimeric H-ATP synthase in the chloroplast of Chlamydomonas reinhardtii

H⁺-ATP synthase is the dominant ATP production site in mitochondria and chloroplasts. So far, dimerization of ATP synthase has been observed only in mitochondria by biochemical and electron microscopic investigations. Although the physiological relevance remains still enigmatic, dimerization was proposed to be a unique feature of the mitochondrion [Biochim. Biophys. Acta 1555 (2002) 154]. It is hard to imagine, however, that closely related protein complexes of mitochondria and chloroplast should show such severe differences in structural organization. We present the first evidences for dimerization of chloroplast ATP synthases within the thylakoid membrane.By investigation of the thylakoid membrane of Chlamydomonas reinhardtii by blue-native polyacrylamide gel electrophoresis, dimerization of the chloroplast ATP synthase was detected. Chloroplast ATP synthase dimer dissociates into monomers upon incubation with vanadate or phosphate but not by incubation with molybdate, while the mitochondrial dimer is not affected by the incubation. This suggests a distinct dimerization mechanism for mitochondrial and chloroplast ATP synthase. Since vanadate and phosphate bind to the active sites, contact sites located on the hydrophilic CF₁ part are suggested for the chloroplast ATP synthase dimer. As the degree of dimerization varies with phosphate concentration, dimerization might be a response to low phosphate concentrations.     

Depolarisation induces rapid and transient formation of intracellular sphingosine-1-phosphate.

Formation of sphingosine-1-phosphate (SPP) by sphingosine kinase serves as a signalling pathway for various membrane receptors. Here, we show that membrane depolarisation is another mechanism by which this pathway can be activated. Formation of [(3)H]SPP as well as levels of endogenous SPP were rapidly and transiently increased in PC12 pheochromocytoma cells depolarised with high KCl. Time course and maximum were similar to those induced by bradykinin. Depolarisation-induced SPP production was also observed in RINm5F insulinoma cells, dependent on extracellular Ca(2+) and fully suppressed by verapamil, thus apparently caused by Ca(2+) influx via voltage-gated Ca(2+) channels. Studies with sphingosine kinase inhibitors and overexpression of sphingosine kinase revealed a partial contribution of this pathway to depolarisation-induced noradrenaline release and Ca(2+) increase.     

Direct Observation of Surface Plasmon Polariton Propagation and Interference by Time-Resolved Imaging in Normal-Incidence Two Photon Photoemission Microscopy

Plasmonics - Time-resolved imaging of the propagation and interference of isolated ultrashort surface plasmon polariton wave packets is demonstrated using two photon photoemission microscopy. The...