Responses in pigmentation and anti-oxidant expression in Arctic Daphnia along gradients of DOC and UV exposure

Responses in carapace melanization and expression of the majoranti-oxidant catalase (CAT) and glutathione transferase (GST)in Arctic Daphnia were assessed in enclosures along a gradientof dissolved organic carbon (DOC). This gradient was createdby adding freeze-dried humic matter to 2 m³ UV-transparent enclosures,yielding final nominal concentrations of 1, 2.5, 5 and 10 mgC l^-1. The UV attenuation was strongly affected by additionsof DOC, and attenuation coefficients at 320 nm increased from3.0 in the control to approximately 3.5 and 11.0 m^-1 in the1 and 10 mg DOC treatments respectively. Most Daphnia showedpronounced carapace melanization, and the absorbance of short-waveradiation through the carapace was strongly related to the degreeof melanization. Nevertheless, the different UV climate in theenclosures did not cause any short-term adaptation in Daphniapigmentation over a 3 week period. The levels of CAT and GSTwere assessed over time in the control and at 10 mg DOC. Theseenzymes displayed opposite patterns, with somewhat lower activitiesof CAT at low DOC (control) relative to 10 mg DOC, while theopposite was found for GST. There was also a significant negativecorrelation between CAT and solar irradiation for GST in bothbags, while no effects were found for GST.     

Tyrant flycatchers coming out in the open: phylogeny and ecological radiation of Tyrannidae (Aves, Passeriformes)

Tyrant flycatchers constitute a substantial component of the land bird fauna in all South American habitats. Past interpretations of the morphological and ecological evolution in the group have been hampered by the lack of a well‐resolved hypothesis of their phylogenetic interrelationships. Here, we present a well‐resolved phylogeny based on DNA sequences from three nuclear introns for 128 taxa. Our results confirm much of the overall picture of Tyrannidae relationships, and also identify several novel relationships. The genera Onychorhynchus, Myiobius and Terenotriccus are placed outside Tyrannidae and may be more closely related to Tityridae. Tyrannidae consists of two main lineages. An expanded pipromorphine clade includes flatbills, tody‐tyrants and antpipits, and also Phylloscartes and Pogonotriccus. The spadebills, Neopipo and Tachuris are their closest relatives. The remainder of the tyrant flycatchers forms a well‐supported clade, subdivided in two large subclades, which differ consistently in foraging behaviour, the perch‐gleaning elaeniines and the sallying myiarchines, tyrannines and fluvicolines. A third clade is formed by the genera Myiotriccus, Pyrrhomyias, Hirundinea and three species currently placed in Myiophobus. Ancestral habitat reconstruction and divergence date estimation suggest that early divergence events in Tyrannida took place in a humid forest environment during the Oligocene. Large‐scale diversification in open habitats is confined to the clade consisting of the elaeniines, myiarchines, tyrannines and fluvicolines. This radiation correlates in time to the expansion of semi‐open and open habitats from the mid‐Miocene (c. 15 Mya) onwards. The pipromorphine, elaeniine and myiarchine–tyrannine–fluvicoline clades each employ distinct foraging strategies (upward striking, perch‐gleaning and sallying, respectively), but the degree of diversity in morphology and microhabitat exploitation is markedly different between these clades. While the pipromorphines and elaeniines each are remarkably homogenous in morphology and exploit a restricted range of microhabitats, the myiarchine–tyrannine–fluvicoline clade is more diverse in these respects. This greater ecological diversity, especially as manifested in their success in colonizing a wider spectrum of open habitats, appears to be connected to a greater adaptive flexibility of the search‐and‐sally foraging behaviour.     

Sulfide induces phosphate release from polyphosphate in cultures of a marine Beggiatoa strain

Sulfur bacteria such as Beggiatoa or Thiomargarita have a particularly high capacity for storage because of their large size. In addition to sulfur and nitrate, these bacteria also store phosphorus in the form of polyphosphate. Thiomargarita namibiensis has been shown to release phosphate from internally stored polyphosphate in pulses creating steep peaks of phosphate in the sediment and thereby inducing the precipitation of phosphorus-rich minerals. Large sulfur bacteria populate sediments at the sites of recent phosphorite formation and are found as fossils in ancient phosphorite deposits. Therefore, it can be assumed that this physiology contributes to the removal of bioavailable phosphorus from the marine system and thus is important for the global phosphorus cycle. We investigated under defined laboratory conditions which parameters stimulate the decomposition of polyphosphate and the release of phosphate in a marine Beggiatoa strain. Initially, we tested phosphate release in response to anoxia and high concentrations of acetate, because acetate is described as the relevant stimulus for phosphate release in activated sludge. To our surprise, the Beggiatoa strain did not release phosphate in response to this treatment. Instead, we could clearly show that increasing sulfide concentrations and anoxia resulted in a decomposition of polyphosphate. This physiological reaction is a yet unknown mode of bacterial polyphosphate usage and provides a new explanation for high phosphate concentrations in sulfidic marine sediments.     

Selection for High Oridonin Yield in the Chinese Medicinal Plant Isodon (Lamiaceae) Using a Combined Phylogenetics and Population Genetics Approach

Oridonin is a diterpenoid with anti-cancer activity that occurs in the Chinese medicinal plant Isodon rubescens and some related species. While the bioactivity of oridonin has been well studied, the extent of natural variation in the production of this compound is poorly known. This study characterizes natural variation in oridonin production in order to guide selection of populations of Isodon with highest oridonin yield. Different populations of I. rubescens and related species were collected in China, and their offspring were grown in a greenhouse. Samples were examined for oridonin content, genotyped using 11 microsatellites, and representatives were sequenced for three phylogenetic markers (ITS, rps16, trnL-trnF). Oridonin production was mapped on a molecular phylogeny of the genus Isodon using samples from each population as well as previously published Genbank sequences. Oridonin has been reported in 12 out of 74 species of Isodon examined for diterpenoids, and the phylogeny indicates that oridonin production has arisen at least three times in the genus. Oridonin production was surprisingly consistent between wild-collected parents and greenhouse-grown offspring, despite evidence of gene flow between oridonin-producing and non-producing populations of Isodon. Additionally, microsatellite genetic distance between individuals was significantly correlated with chemical distance in both parents and offspring. Neither heritability nor correlation with genetic distance were significant when the comparison was restricted to only populations of I. rubescens, but this result should be corroborated using additional samples. Based on these results, future screening of Isodon populations for oridonin yield should initially prioritize a broad survey of all species known to produce oridonin, rather than focusing on multiple populations of one species, such as I. rubescens. Of the samples examined here, I. rubescens or I. japonicus from Henan province would provide the best source of oridonin.     

Enhancer of Polycomb is a suppressor of position-effect variegation in Drosophila melanogaster.

Polycomb group (PcG) genes of Drosophila are negative regulators of homeotic gene expression required for maintenance of determination. Sequence similarity between Polycomb and Su(var)205 led to the suggestion that PcG genes and modifiers of position-effect variegation (PEV) might function analogously in the establishment of chromatin structure. If PcG proteins participate directly in the same process that leads to PEV, PcG mutations should suppress PEV. We show that mutations in E(Pc), an unusual member of the PcG, suppress PEV of four variegating rearrangements: In(l)wm4, B(SV), T(2;3)Sb(V) and In(2R)bw(VDe2). Using reversion of a Pelement insertion, deficiency mapping, and recombination mapping as criteria, homeotic effects and suppression of PEV associated with E(Pc) co-map. Asx is an enhancer of PEV, whereas nine other PcG loci do not affect PEV. These results support the conclusion that there are fewer similarities between PcG genes and modifiers of PEV than previously supposed. However, E(Pc) appears to be an important link between the two groups. We discuss why Asx might act as an enhancer of PEV.     

Sample preparation and high-resolution separation of mycotoxins possessing carboxyl groups

The chromatographic analysis of carboxyl-containing mycotoxins, such as fumonisin B₁, ochratoxin A, and citrinin, presents a continual challenge. Toxins must first be extracted from foods or tissues and then cleaned up before chromatographic separation and detection. Liquid–liquid extraction efficiencies for some carboxylic mycotoxins are marginal for spiked samples and uncertain for incurred residues. Immunoaffinity columns may be useful for concentrating mycotoxins from samples before chromatography. In almost every case, more than one analytical method must be used to confirm the identification of the mycotoxin. The fumonisins are especially troublesome to analyze because they are relatively insoluble in organic solvents, they are not separated easily by gas chromatography, and they do not respond to the usual absorbance or fluorescence detectors used in liquid chromatography. Fluorescence derivatization and electrospray liquid chromatography–mass spectrometry have now made it possible to detect trace levels of mycotoxins. The purity of mycotoxin standards for toxicological studies can be determined by liquid chromatography with either an evaporative light scattering detector or electrospray mass spectrometer. New developments in capillary electrophoresis, nonporous microsphere liquid chromatography, and detection methods for low-volatility compounds show promise for improving the analysis of mycotoxins in the future.