Delayed setting of the photoperiodic response in recombinant clones of the aphid species Sitobion avenae

1. To explore the possible causes of apparent changes in reproductive mode from obligate to cyclical parthenogenesis over time in recombinant clones of the aphid Sitobion avenae Fabricius, all F1 progenies from various crosses were tested for several consecutive years for sexual morph production, after several weeks' exposure to a short photoperiod. 2. Variable proportions of the F1 progenies from selfing and outcrossing holocyclic clones did not produce mating females when induction was attempted in the year of hatching, but only after further induction, the following year or after. This ‘delayed setting of the photoperiodic response’ (DSPR) was much stronger in recombinants from crosses involving only clones from oceanic regions than in those involving one clone from a region with a continental climate. 3. F1 progenies resulting from crosses between one holocyclic and one intermediate clone did not show DSPR. It appeared again in the F2. 4. DSPR preferentially affected the latest hatched clones in a given progeny. 5. This phenomenon is neither an experimental artefact nor as a result of clone contamination. It appears to be because of a genetically controlled quantitative trait affecting the length of the ‘interval timer’, and may represent an adaptation of holocyclic aphid clones from oceanic regions to unpredictable winter climates.     

Translational Control of UIS4 Protein of the Host-Parasite Interface Is Mediated by the RNA Binding Protein Puf2 in Plasmodium berghei Sporozoites

UIS4 is a key protein component of the host-parasite interface in the liver stage of the rodent malaria parasite Plasmodium berghei and required for parasite survival after invasion. In the infectious sporozoite, UIS4 protein has variably been shown to be translated but also been reported to be translationally repressed. Here we show that uis4 mRNA translation is regulated by the P. berghei RNA binding protein Pumilio-2 (PbPuf2 or Puf2 from here on forward) in infectious salivary gland sporozoites in the mosquito vector. Using RNA immunoprecipitation we show that uis4 mRNA is bound by Puf2 in salivary gland sporozoites. In the absence of Puf2, uis4 mRNA translation is de-regulated and UIS4 protein expression upregulated in salivary gland sporozoites. Here, using RNA immunoprecipitation, we reveal the first Puf2-regulated mRNA in this parasite.     

Phylogenetic revision of the Hippasterinae (Goniasteridae; Asteroidea): systematics of deep sea corallivores,including one new genus and three new species

The Hippasterinae is a subfamily within the Goniasteridae, consisting of five genera and 26 species, which occur in cold‐water settings ranging from subtidal to abyssal depths. All known genera were included in a cladistic analysis resulting in two most parsimonious trees, supporting the Hippasterinae as monophyletic. Our review supports Sthenaster emmae gen. et sp. nov. as a new genus and species from the tropical Atlantic and two new Evoplosoma species, Evoplosoma claguei sp. nov. and Evoplosoma voratus sp. nov. from seamounts in the North Pacific. Hippasteria caribaea is reassigned to the genus Gilbertaster, which previously contained a single Pacific species. Our analysis supports Evoplosoma as a derived deep water lineage relative to its continental‐shelf, shallow water sister taxa. The genus Hippasteria contains approximately 15 widely distributed, but similar‐looking species, which occur in the northern and southern hemispheres. Except for Gilbertaster, at least one species in each genus has been observed or is inferred to prey on deep‐sea corals, suggesting that this lineage is important to the conservation of deep‐sea coral habitats. The Hippasterinae shares several morphological similarities with Circeaster and Calliaster, suggesting that they may be related. © 2010 The Linnean Society of London, Zoological Journal of the Linnean Society, 2010, 160 , 266–301.     

Phylogeny of the Zoroasteridae (Zorocallina; Forcipulatida): evolutionary events in deep-sea Asteroidea displaying Palaeozoic features

The Zoroasteridae comprise a small but widespread family of asteroids distributed throughout the deep sea. Although poorly understood, they are often collected in the hundreds, suggesting that they occupy important ecological roles. A phylogenetic analysis including 24 terminal taxa and 70 morphological characters was performed, resulting in a single most-parsimonious tree. The tree separated zoroasterids with open, reticulate skeletons (e.g. Myxoderma ) as more basal than those with more heavily armored, imbricate skeletons (e.g. Zoroaster ), which were more derived. In addition to agreement with established genera, a new genus is supported by the phylogeny as the sister taxon to Myxoderma . The cladistic analysis was performed in conjunction with a revisionary survey of zoroasterid species, resulting in taxonomic changes to species in nearly every genus. Bathymetric and physiographic shifts were observed between the reticulate and imbricate zoroasterid clades. Zoroasterids possess a single marginal plate series, which occurs in basal sister-group neoasteroids (crown-group asteroids). Phylogenetic results suggest that the morphololgical resemblance between zoroasterids and Palaeozoic taxa, such as Calliasterella , is convergent but a paraphyletic Zoroasteride cannot be rejected and remains consistent with basal crown-group affinities. Although the phylogenetic position of the Eocene Zoroaster aff. fulgens was not strongly supported, its presence within a derived cluster of Zoroaster spp. suggests a relatively recent (i.e. Cenozoic) diversification into the deep sea. Taxonomic revisions, and geographical and bathymetric range extensions are also included.  © 2007 The Linnean Society of London, Zoological Journal of the Linnean Society , 2007, 150 , 177–210.     

Olfactory receptors on the antennae of the malaria mosquito Anopheles gambiae are sensitive to ammonia and other sweat-borne components

Electrophysiological studies on female An. gambiae s.s. mosquitoes revealed a receptor neuron within a subpopulation of the antennal grooved-peg sensilla sensitive to the odour of incubated sweat, but not responding to fresh sweat. This receptor neuron was sensitive to ammonia as well, a sweat-borne component which attracts female An. gambiae in a windtunnel bioassay. Neurons innervating a different subpopulation of grooved-peg sensilla did not show a response to incubated sweat. In the latter sensilla, however, one type of neuron responded to water or water containing solutions, while another receptor neuron was inhibited when stimulated with dry air, ether or ethanol. Neurons innervating sensilla trichodea, a more abundant antennal type of olfactory sensillum, did not respond to fresh or incubated sweat at the doses offered. However, receptor neurons within the sensilla trichodea responded with excitation to several sweat-borne components. A subpopulation of the sensilla trichodea was innervated by neurons sensitive to geranyl acetone. A second subpopulation housed receptor neurons sensitive to indole. 3-Methyl-1-butanol and 6-methyl-5-hepten-2-one evoked excitation of receptor neurons within both subpopulations of sensilla trichodea. Neurons were most sensitive to indole and geranyl acetone with a threshold of 0.01%. These findings are discussed in the context of host-seeking behaviour.     

Structural aspects and immunolocalization of the F420-reducing and non-F420-reducing hydrogenases from Methanobacterium thermoautotrophicum Marburg.

The F420-reducing hydrogenase and the non-F420-reducing hydrogenase (EC 1.12.99.1.) were isolated from a crude extract of Methanobacterium thermoautotrophicum Marburg. Electron microscopy of the negatively stained F420-reducing hydrogenase revealed that the enzyme is a complex with a diameter of 15.6 nm. It consists of two ring-like, stacked, parallel layers each composed of three major protein masses arranged in rotational symmetry. Each of these masses appeared to be subdivided into smaller protein masses. Electron microscopy of negatively stained samples taken from intermediate steps of the purification process revealed the presence of enzyme particles bound to inside-out membrane vesicles. Linker particles of 10 to 20 kDa which mediate the attachment of the hydrogenase to the cytoplasmic membrane were seen. Immunogold labelling confirmed that the F420-reducing hydrogenase is a membrane-bound enzyme. Electron microscopy of the negatively stained purified non-F420-reducing hydrogenase revealed that the enzyme is composed of three subunits exhibiting different diameters (5, 4, and 2 to 3 nm). According to immunogold labelling experiments, approximately 70% of the non-F420-reducing hydrogenase protein molecules were located at the cell periphery; the remaining 30% were cytoplasmic. No linker particles were observed for this enzyme.     

Metabolic origin of δ15N values in nitrogenous compounds from Brassica napus L. leaves

Nitrogen isotope composition (δ¹⁵N) in plant organic matter is currently used as a natural tracer of nitrogen acquisition efficiency. However, the δ¹⁵N value of whole leaf material does not properly reflect the way in which N is assimilated because isotope fractionations along metabolic reactions may cause substantial differences among leaf compounds. In other words, any change in metabolic composition or allocation pattern may cause undesirable variability in leaf δ¹⁵N. Here, we investigated the δ¹⁵N in different leaf fractions and individual metabolites from rapeseed (Brassica napus) leaves. We show that there were substantial differences in δ¹⁵N between nitrogenous compounds (up to 30‰) and the content in (¹⁵N enriched) nitrate had a clear influence on leaf δ¹⁵N. Using a simple steady‐state model of day metabolism, we suggest that the δ¹⁵N value in major amino acids was mostly explained by isotope fractionation associated with isotope effects on enzyme‐catalysed reactions in primary nitrogen metabolism. δ¹⁵N values were further influenced by light versus dark conditions and the probable occurrence of alternative biosynthetic pathways. We conclude that both biochemical pathways (that fractionate between isotopes) and nitrogen sources (used for amino acid production) should be considered when interpreting the δ¹⁵N value of leaf nitrogenous compounds.     

A central role for P48/45 in malaria parasite male gamete fertility

Fertilization and zygote development are obligate features of the malaria parasite life cycle and occur during parasite transmission to mosquitoes. The surface protein PFS48/45 is expressed by male and female gametes of Plasmodium falciparum and PFS48/45 antibodies prevent zygote development and transmission. Here, gene disruption was used to show that Pfs48/45 and the ortholog Pbs48/45 from a rodent malaria parasite P. berghei play a conserved and important role in fertilization. p48/45- parasites had a reduced capacity to produce oocysts in mosquitoes due to greatly reduced zygote formation. Unexpectedly, only male gamete fertility of p48/45- parasites was affected, failing to penetrate otherwise fertile female gametes. P48/45 is shown to be a surface protein of malaria parasites with a demonstrable role in fertilization.