Anastral spindle assembly and γ-tubulin in Drosophila oocytes

Background  

Anastral spindles assemble by a mechanism that involves microtubule nucleation and growth from chromatin. It is still uncertain whether γ-tubulin, a microtubule nucleator essential for mitotic spindle assembly and maintenance, plays a role. Not only is the requirement for γ-tubulin to form anastral Drosophila oocyte meiosis I spindles controversial, but its presence in oocyte meiosis I spindles has not been demonstrated and is uncertain.     

Singlet oxygen formation and chlorophyll a triplet excited state deactivation in the cytochrome b6f complex from Bryopsis?corticulans

We have attempted to investigate the correlation between the detergent-perturbed structural integrity of the Cyt b ₆ f complex from the marine green alga Bryopsis corticulans and its photo-protective properties, for which the nonionic detergents n-octyl-β-d-glucopyranoside (β-OG) and n-dodecyl-β-d-maltoside (β-DM), respectively, were used for the preparation of Cyt b ₆ f, and the singlet oxygen (¹O₂*) production as well as the triplet excited-state chlorophyll a (³Chl a*) formation and deactivation were examined by spectroscopic means. Near-infrared luminescence of ¹O₂ * (~1,270 nm) on photo-irradiation was detected for the β-OG preparation where the complex is mainly in oligomeric state, but not for the β-DM one in which the complex exists in dimeric form. Under anaerobic condition, photo-excitation of Chl a in the β-DM preparation generated ³Chl a* with a lower quantum yield of Φ_T ~ 0.02 and a longer lifetime of ~600 μs with respect to those as in the case of β-OG preparation, Φ_T ~ 0.12 and 200–300 μs. These results prove that the enzymatically active and intact Cyt b ₆ f complex on photo-excitation tends to produce little ³Chl a* or ¹O₂ *, which implies that the pigment–protein assembly of Cyt b ₆ f complex per se is crucial for photo-protection. F. Ma and X.-B. Chen contributed equally to this work.     

Interactions of Colletotrichum musae and Lasiodiplodia theobromae and their biocontrol by Pantoea agglomerans and Flavobacterium sp. in expression of crown rot of “Embul” banana

Previous research has shown that two local isolates of bacteria (Pantoea agglomerans and Flavobacterium sp.) are capable of biocontrol of the two main pathogens (Colletotrichum musae and Lasiodiplodia theobromae) known to cause crown rot on “Embul” (Musa, AAB) banana. In this investigation an attempt was made to elucidate the comparative virulence of these pathogens and to determine the underlying biocontrol mechanisms. L. theobromae was more virulent, causing faster spread of the disease, whereas C. musae was more resistant to the bacterial antagonists. Viable cells of the antagonists were more effective at suppressing conidial germination than cell-free culture media. It seemed that antifungal compounds acting on conidial germination may be heat stable and those acting on mycelia may include heat labile compounds also. Considering the specialized roles observed for each pathogen in terms of causing the disease, and in modes of control by antagonists, future field investigations on biocontrol should consider the roles played by the pathogens and the antagonists.

Phylogeny and expression profiling of CAD and CAD-like genes in hybrid Populus (P. deltoides × P. nigra): evidence from herbivore damage for subfunctionalization and functional divergence

Background  

Cinnamyl Alcohol Dehydrogenase (CAD) proteins function in lignin biosynthesis and play a critical role in wood development and plant defense against stresses. Previous phylogenetic studies did not include genes from seedless plants and did not reflect the deep evolutionary history of this gene family. We reanalyzed the phylogeny of CAD and CAD-like genes using a representative dataset including lycophyte and bryophyte sequences. Many CAD/CAD-like genes do not seem to be associated with wood development under normal growth conditions. To gain insight into the functional evolution of CAD/CAD-like genes, we analyzed their expression in Populus plant tissues in response to feeding damage by gypsy moth larvae (Lymantria dispar L.). Expression of CAD/CAD-like genes in Populus tissues (xylem, leaves, and barks) was analyzed in herbivore-treated and non-treated plants by real time quantitative RT-PCR.     

Obtaining and characterization of “Holospora curviuscula” and Holospora obtusa, bacterial symbionts of the macronuclei of Paramecium bursaria and Paramecium caudatum

The symbionts of the macronuclei of Paramecium bursaria and P. caudatum, “Holospora curviuscula” 02AZ16 and H. obtusa 88Ti, respectively, were obtained and investigated. The 16S rDNA nucleotide sequences of “Holospora curviuscula” were obtained for the first time. The differences in 16S rDNA (3.4%) suggest their classification within the genus Holospora. Molecular phylogenetic analysis of the symbionts revealed that these intranuclear symbionts of the ciliates belonged to the order Rickettsiales, forming within a compact cluster of related species.     

Ethanol-hypersensitive and ethanol-dependent cdc? mutants in Schizosaccharomyces pombe

Ethanol-hypersensitive strains (ets mutants), unable to grow on media containing 6% ethanol, were isolated from a sample of mutagenized Schizosaccharomyces pombe wild-type cells. Genetic analysis of these ets strains demonstrated that the ets phenotype is associated with mutations in a large set of genes, including cell division cycle (cdc) genes, largely non-overlapping with the set represented by the temperature conditional method; accordingly, we isolated some ets non-ts cdc ^– mutants, which may identify novel essential genes required for regulation of the S. pombe cell cycle. Conversely, seven well characterized ts cdc ^– mutants were tested for their ethanol sensitivity; among them, cdc1–7 and cdc13–117 exhibited a tight ets phenotype. Ethanol sensitivity was also tested in strains bearing different alleles of the cdc2 gene, and we found that some of them were ets, but others were non-ets; thus, ethanol hypersensitivity is an allele-specific phenotype. Based on the single base changes found in each particular allele of the cdc2 gene, it is shown that a single amino acid substitution in the p34^cdc2 gene product can produce this ets phenotype, and that ethanol hypersensitivity is probably due to the influence of this alcohol on the secondary and/or tertiary structure of the target protein. Ethanol-dependent (etd) mutants were also identified as mutants that can only be propagated on ethanol-containing media. This novel type of conditional phenotype also covers many unrelated genes. One of these etd mutants, etd1-1, was further characterized because of the lethal cdc ^– phenotype of the mutant cells under restrictive conditions (absence of ethanol). The isolation of extragenic suppressors of etd1-1, and the complementation cloning of a DNA fragment encompassing the etd1 ⁺ wild-type gene (or an extragenic multicopy suppressor) demonstrate that current genetic techniques may be applied to mutants isolated by using ethanol as a selective agent.     

Retrofitting BACs with G418 resistance, luciferase, and oriP and EBNA-1 – new vectors for in vitro and in vivo delivery

Background  

Bacterial artificial chromosomes (BACs) have been used extensively for sequencing the human and mouse genomes and are thus readily available for most genes. The large size of BACs means that they can generally carry intact genes with all the long range controlling elements that drive full levels of tissue-specific expression. For gene expression studies and gene therapy applications it is useful to be able to retrofit the BACs with selectable genes such as G418 resistance, reporter genes such as luciferase, and oriP/EBNA-1 from Epstein Barr virus which allows long term episomal maintenance in mammalian cells.     

Genetic and morphological variation in the venus clam Cyclina?sinensis along the coast of China

Six geographic samples of Cyclina sinensis were collected from the coast along China and analyzed to reveal morphological and genetic variation by using nine allozyme loci and 11 morphological variables. The discriminant function analysis (DFA) of morphology suggested a clear separation between the southern and northern populations. Polymorphism was detected at nine loci across all six populations. The mean allele number ranged from 2.44 to 2.78, and the mean observed heterozygosity ranged from 0.218 to 0.296. High level of genetic differentiation was found between three northern populations and three southern populations. The marked genetic differentiation can be explained by the upwelling of the Zhejiang province and the freshwater outflow of Yangtze River. The results obtained in this study indicate that the northern and southern populations of C. sinensis should be treated as separate units for conservation management.     

Eulophidae (hymenoptera) parasitoids of Phyllonorycter apparella and phyllonorycter populifoliella (Lepidoptera, Gracillariidae), pests of Populus tremula and populus nigra in Ul’yanovsk province, Russia

Parasitoid complexes of two species of the genus Phyllonorycter (Ph. apparella and Ph. populifoliella) reared from 2 plants (Populus tremula and P. nigra) were studied in Ul’yanovsk Province, Russia. Twenty species of parasitoids are new for Ph. apparella and 12 are new for Ph. populifoliella. Minotetrastichus frontalis and Pnigalio agraules are the dominant species for both parasitoid complexes. The highest relative abundance was observed for Ph. apparella on Populus tremula (75%) and for Ph. populifoliella on P. nigra (61%). The parasitoid complexes of Ph. apparella and Ph. populifoliella show high similarity (the Jaccard coefficient is 0.65).     

Circadian rhythm of (Z)- and (E)-2-β-d-glucopyranosyloxy-4-methoxy cinnamic acids and herniarin in leaves of Matricaria chamomilla

Chamomile (Matricaria chamomilla) in the above-ground organs synthesizes and accumulates (Z)- and (E)-2-β-d-glucopyranosyloxy-4-methoxy cinnamic acids (GMCA), the precursors of phytoanticipin herniarin (7-methoxycoumarin). The diurnal rhythmicity of the sum of GMCA (maximum before daybreak) and herniarin (acrophase at 10 h 21 min of circadian time) was observed under artificial lighting conditions LD 12:12. The acrophase is the time point of the maximum of the sinusoidal curve fitted to the experimental data. In continuous light, the circadian rhythms of both compounds were first described with similar acrophases of endogenous rhythms; a significantly different result from that in synchronized conditions. The rhythms’ mesor (the mean value of the sinusoidal curve fitted to the experimental data) under free-running conditions was not influenced. Abiotic stress under synchronized conditions decreased the average content of GMCA to half of the original level and eliminated the rhythmicity. In contrast, the rhythm of herniarin continued, though its content significantly increased. Nitrogen deficiency resulted in a significant increase in GMCA content, which did not manifest any rhythmicity while the rhythm of herniarin continued. Circadian control of herniarin could be considered as a component of the plant’s specialized defence mechanisms.     

DnaK-dependent ribosome biogenesis in Escherichia coli? : competition for dominance between the alleles dnaK756 and dnaK ?+

The Escherichia coli chaperone DnaK is vital for many cellular functions, including ribosome biogenesis at high temperature. Thus, the dnaK756-ts (λ ^R ) mutant, at the non-permissive temperature, is inhibited at a late stage of ribosome assembly, yielding 21S, 32S and 45S precursor particles. This defect, unlike the λ resistance and thermosensitivity phenotypes, is not complemented by lysogenisation with a transducing phage λ dnaK ⁺ bearing the wild-type dnaK gene. However this dominant phenotype becomes recessive when dnaK ⁺ is expressed from a medium-copy-number plasmid. On the other hand, an excess of DnaK causes an unexpected dominant-lethal effect of the dnaK756 allele near non-permissive temperatures. This interplay between the dnaK ⁺ and dnaK756 alleles supports the idea of that DnaK oligomers form in the cell. Received: 28 April 1998 / Accepted: 24 July 1998     

Are Polyommatus hispana and Polyommatus slovacus bivoltine Polyommatus coridon (Lepidoptera: Lycaenidae)? The discriminatory value of genetics in taxonomy

Taxonomic confusion exists in several sibling species groups. The Polyommatus coridon species complex (Chalk Hill Blues) serves as a model group of sibling species in which genetic analyses provide suitable means for taxonomic clarification. We studied the allozyme patterns of the two described bivoltine species of this complex, Polyommatus hispana and Polyommatus slovacus, and compared them to the two genetic lineages of the univoltine P. coridon. P. hispana is well distinguished from P. coridon (genetic distance: 0.081), and most probably is a sibling species that has evolved during glacial isolation on the Iberian Peninsula. P. slovacus is genetically indistinguishable from the eastern, Pontic–Mediterranean lineage of P. coridon; therefore we suggest that it represents a local bivoltine population only. Since the spring generation of P. slovacus was much less common than the summer generation and showed less genetic diversity, it is probable that uni-/bivoltinism is a dimorphism affecting only part of the whole population. We suggest that the higher genetic diversity of the second generation may be a consequence of gene flow from adjacent single-brooded populations.     

Apyrase and α-glucosidase in the salivary glands of Aedes albopictus

An apyrase and an α-glucosidase were detected in the salivary glands extracts of adult Aedes albopictus. The apyrase is a 61,000 Da secreted protein that hydrolyses ATP and ADP. This protein is synthesized in adults and is preferentially accumulated in the distal lateral lobes of the female salivary glands. The α-glucosidase is a secreted 67,000 Da protein. This enzyme is synthesized during adult life and accumulated in the proximal-lateral lobes of both males and females. The results are discussed and compared with data previously obtained with Aedes aegypti salivary glands.     

Takeoff flight performance and plumage wettability in Cassin’s Auklet Ptychoramphus aleuticus, Xantus’s Murrelet Synthliboramphus hypoleucus and Leach’s Storm-petrel Oceanodroma leucorhoa

Due to their marine habitats and distinctive foraging modes, seabirds face unique challenges with respect to flying that are negotiated differently by various species. One such challenge is taking off from the water with wet plumage. This study evaluated plumage wettability and takeoff performance in three seabird species: two wing-propelled divers with high wing loading, Cassin’s Auklet Ptychoramphus aleuticus and Xantus’s Murrelet Synthliboramphus hypoleucus; and Leach’s Storm-petrel Oceanodroma leucorhoa, a surface feeder with low wing loading. The plumages of the diving birds held less water than that of O. leucorhoa (~6.7% of body mass vs 9.5%). This difference is explained by O. leucorhoa’s surface to volume ratio being larger than that of the alcids. Furthermore, the alcids have afterfeathers larger than those of O. leucorhoa, which promotes a better insulation during diving. Examination of takeoff performance both before and after experimentally submerging the birds indicated that wingbeat frequency, speed and mass-specific power (peak and mean), and energy per wingbeat decreased in all species when plumage was experimentally wetted, whereas mean acceleration increased. O. leucorhoa was more strongly affected by wet plumage than the alcids, with a 32% of reduction in mass-specific energy per wingbeat compared to ≤25% in the alcids. Takeoff angle was reduced in alcids, but not significantly so in O. leucorhoa. Our results offer insights into the takeoff mechanics problems of wet seabirds given their differences in life history and morphology.     

Somatic embryogenesis and plant regeneration in diploid Allium fistulosum × A. cepa F1 hybrid onions

Procedures were developed for disinfestation of non-dormant basal plate tissue excised from field grown basal plate tissue of diploid Allium fistulosum × A. cepa F₁ hybrid onions. Contamination levels varied with the season and vegetative development of plant material. Callus initiated from basal plate tissue and immature inflorescences of the F₁ hybrids was maintained on a BDS-based medium containing 0.75 mg/l picloram and 2.0 mg/l BA. When this medium was supplemented with vitamins and glycine, and with proline at 2.5 gm/1, somatic embryos began to form. Their development continued on a BDS-based shoot promotion medium containing 0.03 mg/l picloram and 0.32 mg/l 2iP supplemented with vitamins, glycine and proline. Genotypes differed significantly in the numbers of structures regenerated. Plantlets from somatic embryos were rooted into BDS or half-strength BDS medium without growth substances and were successfully transferred to sterilized potting mix in plastic commercial corsage boxes.Abbreviations BA benzyladenine - 2,4-D 2,4-dichlorophenoxyacetic acid - picloram 4-amino-3,5,6-trichloropicolinic acid - 2iP N6-(2-isopentenyl)adenine - NAA 1-naphthylacetic acid - BDS Gamborg's B5 medium modified by Dunstan and Short (1977a)     

Tagesaktivit?t, Nestbaumethode und Brutverhalten des HonigsaugersNectarinia (Aidemonia)kilimensis in Zentralafrika

Zusammenfassung Ein Paar des HonigsaugersNectarinia kilimensis wurde in der Brutzeit beim Nestbau 21 Stunden beobachtet. Über die Bauaktivität gibt Abb. 2 Aufschluß. 140 von 144 Anflügen mit Nistmaterial waren auf 8 Stunden von 8^h–16^h konzentriert. Das Nistmaterial bestand fast ausschließlich aus Halmen, Pflanzenwolle und Spinnweben; dieses Material wurde von Anfang an abwechselnd verwendet. Nur das hat gebaut. Die Baumethoden werden beschrieben, ebenso verschiedene Balzhandlungen des . Der Nestbau dauerte 4 1/2, beim folgenden Nest 3 1/2 Tage.Beim Brüten waren Schnabel und Oberkopf des sichtbar. Während der Bauzeit wurde ein ausgeflogenes juv. nur vom gefüttert. Als es mindestens 17 Tage alt war, wurde es vom , 6 Tage später auch vom aggressive gejagt, doch war dieses juv. mehr als 3 Wochen nach dem Ausfliegen noch im Revier.

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Day-time activity, nest-building method and breeding behaviour of Bronze SunbirdNectarinia (Aidemonia) kilimensis in Central Africa

Summary A pair of Bronze SunbirdsNectarinia kilimensis was observed nest building over a period of 21 hours in the breeding season. Fig. 2 gives information on building activity. Of 144 arrivals with nest material 140 were concentrated in 8 hours from 08.00 to 16.00 hrs. Nest material consisted almost exclusively of grasses, plants, down and spider's webs; this material was, from the outset, used in an alternating pattern. The alone did the building. Nest-building methods are described, also various courtship activities of the . Nest building took 4 1/2 days, in the case of a second nest, 3 1/2 days.The 's bill and crown were visible when she was incubating. One young that had left the nest was fed by the alone. At least 17 days after this young one had fledged, it was chased aggressively by the , 6 days later also by the ; despite this, the same young bird was still in the territory more than three weeks after it had fledged.

     

Chemistry of Cirsium and Carduus: a role in ecological risk assessment for biological control of weeds?

Prediction of host plant range and ecological impact of exotic phytophagous insects, such as insects for classical biological control of weeds, represents a major challenge. Recently, the flowerhead weevil (Rhinocyllus conicus Fröl.), introduced from Europe into North America to control exotic thistles (Carduus spp.), has become invasive. It feeds heavily on some, but not all species of native North American thistles (Cirsium spp.). We hypothesized that such non-target use among native plants could be better predicted by knowledge of characteristic chemical profiles of secondary compounds to supplement the results of host specificity testing. To evaluate this hypothesis, we reviewed the literature on the chemistry of Cirsium and Carduus thistles. We asked what compounds are known to be present, what is known about their biological activity, and whether such information on chemical profiles would have better predicted realized host range and ecological effects of R. conicus in North America. We found an extensive, but incomplete literature on the chemistry of true thistles. Two main patterns emerged. First, consistent chemical similarities and interesting differences occur among species of thistles. Second, variation occurs in biologically active groups of characteristic compounds, specifically flavonoids, sterols, alkaloids and phenolic acids, that are known to influence host plant acceptance, selection, and feeding by phytophagous insects. Surprisingly, sesquiterpene lactones, which are characterisitic in closely related Asteraceae, have not been extensively reported for Cirsium or Carduus. The minimal evidence on sesquiterpene lactones may reflect extraction methods vs. true absence. In summary, our review suggests further research on thistle chemistry in insect feeding is warranted. Also, since the exotic Canada thistle (Cirsium arvense) is an invasive thistle of current concern in North America, such research on mechanisms underlying host range expansion by exotic insects would be useful.     

How many heteropteran species can live on alien goldenrods Solidago canadensis and S. gigantea in Europe?

During the vegetation periods of 2001–2003 Heteroptera associated with the invasive alien tall goldenrods Solidago canadensis and S. gigantea were studied in seven model habitats in the north-eastern part of the Czech Republic. Heteropterans associated with adjacent growths were also studied in 2002–2003. A set of 3,042 specimens of 127 samples was analyzed with the aim of estimating average species richness, abundance and trophic structure of the heteropteran assemblages of the studied plant stand. On alien Solidago, 68 heteropteran species were recorded and 71 species were collected in the stands adjacent to the tall goldenrods with 48 shared species. Despite the nearly indentical species richness and similar abundances in Solidago and adjacent stands, there are differences in the trophic structure. The majority of the shared species and species found on Solidago canadensis only are polyphagous contrary to the majority of stenophagous species found on Solidago free stands only. Only a small proportion of heteropteran species that were recorded on alien Solidago stands are specialized to Asteraceae and their abundance was mostly low. Only the lygaeid Nysius senecionis, an Asteraceae specialist, occured in masses on S. canadensis in sunny and warm habitats. Similarly, predatory Orius minutus and O. niger reached high abundance values in Solidago stands compared to adjacent stands.