Natural hybridization in tropical spikerushes of Eleocharis subgenus Limnochloa (Cyperaceae): Evidence from morphology and DNA markers

? Premise of the study: Natural hybridization represents an important force driving plant evolution and affecting community structure and functioning. Hybridization may be overlooked, however, among morphologically highly uniform congeners. An excellent example of such a group is Eleocharis subgenus Limnochloa, which has no reliably proven hybrids. Does this reflect biological barriers to interspecific crosses or difficulties in detecting the hybrids? We tested the hypothesis that hybridization occurs among sympatric Eleocharis cellulosa, E. interstincta, and E. mutata in northern Belize, Central America. ? Methods: Morphometric study (407 plants) was followed by examination of inter-simple sequence repeat (ISSR) polymorphisms (44 plants) and ITS sequence variation (33 plants). ? Key results: Two putatively hybrid morphotypes were discerned-E. cellulosa-resembling and E. interstincta-resembling. DNA markers of E. cellulosa and E. interstincta displayed additive constitution in plants from one E. cellulosa-resembling population only. The other putatively hybrid populations contained ISSR and ITS markers of the species they resembled morphologically, several unique ISSR markers, and ITS sequences of an undescribed South American Limnochloa entity. DNA markers of E. mutata were absent in the putative hybrids. ? Conclusions: Simultaneous use of various types of molecular markers can overcome many pitfalls of investigations concerning hybridization among closely related and morphologically similar species. Northern Belize represents a hybrid zone of E. cellulosa and E. interstincta. A third participant in the hybridization events occurring in this zone is an unknown Limnochloa lineage but is not E. mutata. Interspecific hybridization may play a significant role in the diversification of Eleocharis.     

Variation in the spectrum of Fusarium species on winter wheat

In 1998–2000 a monitoring of the spectrum of Fusarium species on winter wheat was carried out in the Rhineland. The epidemic spread ofFusarium spp. on wheat plants during growing season was investigated as well as the grain contamination after harvest.F avenaceum was the Fusarium species isolated most frequently followed byF culmorum, F poae andF graminearum. Microdochium nivale occurred considerably only in 1998. Both, susceptibility and plant height of the cultivars were correlated to the incidence of Fusarium species /M nivale on harvested kernels; interactions with cropping intensities were detected. The incidence ofF poae seemed to be independent of the cultivar-specific Fusarium susceptibility. Despite the lack of disease symptoms, between growth stages 45–85 mycelium ofFusarium spp. was detectable in the leaves as well as conidia on the leaf surfaces.     

Yield reduction and mycotoxin contamination of wheat due to<Emphasis Type="Italic">Fusarium culmorum</Emphasis>

The inoculation of wheat ears with 27 isolates ofFusarium culmorum in growth stage 65 reduced 1000-grain weights by 14 to 61%. For the phytopathological characterisation of isolates the virulence on primary wheat leaves and the growth rate an potato-dextrose-agar were assessed. Deoxynivalenol-producing isolates ofF. culmorum reduced the 1000-grain weight more than nivalenol-producing isolates.     

Identification of a gammaherpesvirus selective chemokine binding protein that inhibits chemokine action

Chemokines are involved in recruitment and activation of hematopoietic cells at sites of infection and inflammation. The M3 gene of gammaHV68, a gamma-2 herpesvirus that infects and establishes a lifelong latent infection and chronic vasculitis in mice, encodes an abundant secreted protein during productive infection. The M3 gene is located in a region of the genome that is transcribed during latency. We report here that the M3 protein is a high-affinity broad-spectrum chemokine scavenger. The M3 protein bound the CC chemokines human regulated upon activation of normal T-cell expressed and secreted (RANTES), murine macrophage inflammatory protein 1alpha (MIP-1alpha), and murine monocyte chemoattractant protein 1 (MCP-1), as well as the human CXC chemokine interleukin-8, the murine C chemokine lymphotactin, and the murine CX(3)C chemokine fractalkine with high affinity (K(d) = 1. 6 to 18.7 nM). M3 protein chemokine binding was selective, since the protein did not bind seven other CXC chemokines (K(d) > 1 microM). Furthermore, the M3 protein abolished calcium signaling in response to murine MIP-1alpha and murine MCP-1 and not to murine KC or human stromal cell-derived factor 1 (SDF-1), consistent with the binding data. The M3 protein was also capable of blocking the function of human CC and CXC chemokines, indicating the potential for therapeutic applications. Since the M3 protein lacks homology to known chemokines, chemokine receptors, or chemokine binding proteins, these studies suggest a novel herpesvirus mechanism of immune evasion.     

Is there evidence of fetal-maternal heart rate synchronization?

Background

The prenatal condition offers a unique possibility of examining physiological interaction between individuals. Goal of this work was to look for evidence of coordination between fetal and maternal cardiac systems.

Methods

177 magnetocardiograms were recorded in 62 pregnancies (16^th–42^nd week of gestation). Fetal and maternal RR interval time series were constructed and the phases, i.e. the timing of the R peaks of one time series in relation to each RR interval of the other were determined. The distributions of these phases were examined and synchrograms were constructed for real and surrogate pairs of fetal and maternal data sets. Synchronization epochs were determined for defined n:m coupling ratios.

Results

Differences between real and surrogate data could not be found with respect to number of synchronization epochs found (712 vs. 741), gestational age, subject, recording or n:m combination. There was however a preference for the occurrence of synchronization epochs in specific phases in real data not apparent in the surrogate for some n:m combinations.

Conclusion

The results suggest that occasional coupling between fetal and maternal cardiac systems does occur.

     

Independence of Evolutionary and Mutational Rates after Transmission of Avian Influenza Viruses to Swine

In 1979, an H1N1 avian influenza virus crossed the species barrier, establishing a new lineage in European swine. Because there is no direct or serologic evidence of previous H1N1 strains in these pigs, these isolates provide a model for studying early evolution of influenza viruses. The evolutionary rates of both the coding and noncoding changes of the H1N1 swine strains are higher than those of human and classic swine influenza A viruses. In addition, early H1N1 swine isolates show a marked plaque heterogeneity that consistently appears after a few passages. The presence of a mutator mutation was postulated (C. Scholtissek, S. Ludwig, and W. M. Fitch, Arch. Virol. 131:237–250, 1993) to account for these observations and the successful establishment of an avian H1N1 strain in swine. To address this question, we calculated the mutation rates of A/Mallard/New York/6750/78 (H2N2) and A/Swine/Germany/2/81 (H1N1) by using the frequency of amantadine-resistant mutants. To account for the inherent variability of estimated mutation rates, we used a probabilistic model for the statistical analysis. The resulting estimated mutation rates of the two strains were not significantly different. Therefore, an increased mutation rate due to the presence of a mutator mutation is unlikely to have led to the successful introduction of avian H1N1 viruses in European swine.Influenza viruses undergo rapid variation in nature, thereby limiting prevention of epidemics and pandemics (20). Therefore, questions regarding their evolution remain important, and the answers may yield information useful for predicting further antigenic changes and for explaining the occurrence of new pandemic strains. In 1979, an H1N1 influenza virus of avian origin was transmitted to pigs in northern Europe, thereby introducing a new stable lineage (22, 26). Because there is no direct or serologic evidence of previous H1N1 strains in these pigs (35), we do not need to extrapolate the point of introduction from evolutionary changes over time. Therefore, the European swine influenza H1N1 viruses are a model for studying the early evolution of influenza virus strains in a new host after their introduction in the absence of reassortment.Several characteristics of these H1N1 swine viruses make them particularly interesting for studying the evolution of influenza viruses. Analysis of phylogenic data on their HA, NP, M, and NS genes revealed that the evolutionary rates of both the coding and noncoding changes of these strains are up to 54% higher than those of human and classic swine viruses (18, 33). Such higher evolutionary rates might be due to positive Darwinian selection in avian-like swine influenza viruses, reflecting adaptation to a new host; to differences in sampling frequencies (10) of the viral lineages compared; or to a higher mutation rate. The elevated rate of noncoding changes might be due to fixation of linked coding changes. In addition, early H1N1 swine viruses show a marked plaque heterogeneity and an unusually high escape rate in the presence of various monoclonal antibodies (18). These observations suggest that at least one other factor, independent from positive selection of advantageous variants, must have influenced the evolution of the swine H1N1 isolates since 1979. One candidate is the presence of a mutator mutation (24). An initial variant could have a mutation in its polymerase complex that caused it to be more error prone and to generate a broader spectrum of variants. Such a polymerase might be detrimental for an established strain but advantageous under stress conditions such as adaptation to a new environment. After that, variants with a less error-prone polymerase might again become predominant in the population (18).We wanted to determine whether increased mutation rates due to the presence of a mutator mutation might have contributed to the establishment of the European swine H1N1 viruses. To this end, we calculated the mutation rates of A/Swine/Germany/2/81, a well-characterized early H1N1 swine isolate, and A/Mallard/New York/6750/78 (H2N2), a well-established avian isolate; the evolution of avian influenza viruses is considerably slower than that of classic swine and human isolates (16). An avian H1N1 precursor virus was not available for study. To accommodate the inherent high variability of estimated mutation rates, we developed a new probabilistic model (see Appendix) to calculate the mutation rate and its standard deviation (SD) and screened several parallel clones. To facilitate rapid screening of parallel cultures, we evaluated the frequency with which amantadine-resistant mutants developed. Our results suggest that the mutation rates of A/Swine/Germany/2/81 and A/Mallard/New York/6750/78 are not significantly different and fail to reflect their very different evolutionary backgrounds.     

The murine gammaherpesvirus 68 v-cyclin gene is an oncogene that promotes cell cycle progression in primary lymphocytes

Several gammaherpesviruses contain open reading frames encoding proteins homologous to mammalian D-type cyclins. In this study, we analyzed the expression and function of the murine gammaherpesvirus 68 (gammaHV68) viral cyclin (v-cyclin). The gammaHV68 v-cyclin gene was expressed in lytically infected fibroblasts as a leaky-late mRNA of approximately 0.9 kb encoding a protein of approximately 25 kDa. To evaluate the effect of the gammaHV68 v-cyclin on cell cycle progression in primary lymphocytes and to determine if the gammaHV68 v-cyclin gene is an oncogene, we generated transgenic mice by using the lck proximal promoter to express the gammaHV68 v-cyclin in early T cells. Expression of the gammaHV68 v-cyclin significantly increased the number of thymocytes in cell culture, as determined by measuring both DNA content and incorporation of 5-bromo-2-deoxyuridine following in vivo pulse-labeling. Expression of the gammaHV68 v-cyclin interfered with normal thymocyte maturation, as shown by increased numbers of CD4(+) CD8(+) double-positive thymocytes and decreased numbers of CD4(+) or CD8(+) single-positive and T-cell-receptor-bright thymocytes and splenocytes in transgenic mice. Despite increased numbers of cycling thymocytes, gammaHV68-v-cyclin-transgenic mice did not have proportionately increased thymocyte numbers, and staining by terminal deoxynucleotidyltransferase-mediated dUTP-biotin nick end labeling demonstrated increased apoptosis in the thymi of v-cyclin-transgenic mice. Fifteen of 38 gammaHV68-v-cyclin-transgenic mice developed high-grade lymphoblastic lymphoma between 3 and 12 months of age. We conclude that (i) the gammaHV68 v-cyclin is expressed as a leaky-late gene in lytically infected cells, (ii) expression of the gammaHV68 v-cyclin in thymocytes promotes cell cycle progression and inhibits normal T-cell differentiation, and (iii) the gammaHV68 v-cyclin gene is an oncogene.     

New species and new record of Tetranychus Dufour from Australia, with a key to the major groups in this genus based on females (Acari: Prostigmata: Tetranychidae)

A new species of spider mite, Tetranychus bunda sp. n., is described and illustrated from Australia. It was found damaging the foliage of Desmodium tortuosum (Sw.) DC. (Fabaceae) in Darwin, Northern Territory. In addition, the geographical range of Tetranychus fijiensis Hirst is extended to include Australia. This species was found in the Northern Territory feeding on frangipani ( Plumeria sp., Apocynaceae), betel palm ( Areca catechu L., Arecaceae) and Macarthur feather palm ( Ptychosperma macarthurii [H. Wendl. ex Veitch] (H. Wendl. ex Hook. f., Arecaceae)). Details of the biology of T. bunda sp. n. and T. fijiensis are given. A key to the major groups of Tetranychus Dufour of the world, based on females, is presented and species known to occur in Australia are outlined.     

Microbial Phototrophic, Heterotrophic, and Diazotrophic Activities Associated with Aggregates in the Permanent Ice Cover of Lake Bonney, Antarctica

Abstract The McMurdo Dry Valley lakes, Antarctica, one of the Earth's southernmost ecosystems containing liquid water, harbor some of the most environmentally extreme (cold, nutrient-deprived) conditions on the planet. Lake Bonney has a permanent ice cover that supports a unique microbial habitat, provided by soil particles blown onto the lake surface from the surrounding, ice-free valley floor. During continuous sunlight summers (Nov.-Feb.), the dark soil particles are heated by solar radiation and melt their way into the ice matrix. Layers and patches of aggregates and liquid water are formed. Aggregates contain a complex cyanobacterial-bacterial community, concurrently conducting photosynthesis (CO2 fixation), nitrogen (N2) fixation, decomposition, and biogeochemical zonation needed to complete essential nutrient cycles. Aggregate-associated CO2- and N2-fixation rates were low and confined to liquid water (i.e., no detectable activities in the ice phase). CO2 fixation was mediated by cyanobacteria; both cyanobacteria and eubacteria appeared responsible for N2 fixation. CO2 fixation was stimulated primarily by nitrogen (NO3-), but also by phosphorus (PO43-). PO43- and iron (FeCl3 + EDTA) enrichment stimulated of N2 fixation. Microautoradiographic and physiological studies indicate a morphologically and metabolically diverse microbial community, exhibiting different cell-specific photosynthetic and heterotrophic activities. The microbial community is involved in physical (particle aggregation) and chemical (establishing redox gradients) modification of a nutrient- and organic matter-enriched microbial "oasis," embedded in the desertlike (i.e., nutrient depleted) lake ice cover. Aggregate-associated production and nutrient cycling represent microbial self-sustenance in a microenvironment supporting "life at the edge," as it is known on Earth.     

How many species of Isothecium (Lembophyllaceae,Bryophyta) are there in Macaronesia? A survey using integrative taxonomy

Species boundaries are sometimes difficult to assess, especially when molecular data do not neatly match morphologically defined units. This study investigates the moss genus Isothecium, with special emphasis on Macaronesian populations. Morphological studies are combined with the analysis of three rapidly evolving markers: nuclear internal transcribed spacer and plastid trnG and trnL‐trnF. The results of the morphological studies suggest that Isothecium is represented by five species in Macaronesia, including a new endemic species from Madeira, I sothecium montanum sp. nov. , which is described here. The molecular results are less conclusive than the morphology results in delimiting species of this genus, even when indels are included as informative. Once possible methodological shortcomings have been discarded, the results can be interpreted as having been caused by incomplete lineage sorting, probably as a consequence of recent speciation. The molecular results also suggest that the origin of the Macaronesian endemics may be explained by at least two independent colonization events. Finally, the delimitation of a new endemic species of Isothecium in Macaronesia indicates that current knowledge on the taxonomy of spore‐producing plants may be far from complete in this hotspot of biodiversity. © 2015 The Linnean Society of London, Botanical Journal of the Linnean Society, 2015, 00 , 000–000.