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Lily Khadempour Valerie LeMay David Jack J?rg Bohlmann Colette Breuil 《Microbial ecology》2012,64(4):909-917
The mountain pine beetle (MPB) is a native bark beetle of western North America that attacks pine tree species, particularly lodgepole pine. It is closely associated with the ophiostomatoid ascomycetes Grosmannia clavigera, Leptographium longiclavatum, Ophiostoma montium, and Ceratocystiopsis sp.1, with which it is symbiotically associated. To develop a better understanding of interactions between beetles, fungi, and host trees, we used target-specific DNA primers with qPCR to assess the changes in fungal associate abundance over the stages of the MPB life cycle that occur in galleries under the bark of pine trees. Multivariate analysis of covariance identified statistically significant changes in the relative abundance of the fungi over the life cycle of the MPB. Univariate analysis of covariance identified a statistically significant increase in the abundance of Ceratocystiopsis sp.1 through the beetle life cycle, and pair-wise analysis showed that this increase occurs after the larval stage. In contrast, the abundance of O. montium and Leptographium species (G. clavigera, L. longiclavatum) did not change significantly through the MPB life cycle. From these results, the only fungus showing a significant increase in relative abundance has not been formally described and has been largely ignored by other MPB studies. Although our results were from only one site, in previous studies we have shown that the fungi described were all present in at least ten sites in British Columbia. We suggest that the role of Ceratocystiopsis sp.1 in the MPB system should be explored, particularly its potential as a source of nutrients for teneral adults. 相似文献
3.
Kevin J. Beiler Suzanne W. Simard Valerie LeMay Daniel M. Durall 《Molecular ecology》2012,21(24):6163-6174
Understanding ectomycorrhizal fungal (EMF) community structure is limited by a lack of taxonomic resolution and autecological information. Rhizopogon vesiculosus and Rhizopogon vinicolor (Basidiomycota) are morphologically and genetically related species. They are dominant members of interior Douglas‐fir (Pseudotsuga menziesii var. glauca) EMF communities, but mechanisms leading to their coexistence are unknown. We investigated the microsite associations and foraging strategy of individual R. vesiculosus and R. vinicolor genets. Mycelia spatial patterns, pervasiveness and root colonization patterns of fungal genets were compared between Rhizopogon species and between xeric and mesic soil moisture regimes. Rhizopogon spp. mycelia were systematically excavated from the soil and identified using microsatellite DNA markers. Rhizopogon vesiculosus mycelia occurred at greater depth, were more spatially pervasive, and colonized more tree roots than R. vinicolor mycelia. Both species were frequently encountered in organic layers and between the interface of organic and mineral horizons. They were particularly abundant within microsites associated with soil moisture retention. The occurrence of R. vesiculosus shifted in the presence of R. vinicolor towards mineral soil horizons, where R. vinicolor was mostly absent. This suggests that competition and foraging strategy may contribute towards the vertical partitioning observed between these species. Rhizopogon vesiculosus and R. vinicolor mycelia systems occurred at greater mean depths and were more pervasive in mesic plots compared with xeric plots. The spatial continuity and number of trees colonized by genets of each species did not significantly differ between soil moisture regimes. 相似文献
4.
We have used immunocytochemistry and molecular cloning methods to identify and characterize structural polypeptides of the centromere. These studies permit us to resolve two distinct regions: the inner and outer centromere. (i) Components of the outer centromere: autoantibodies from certain patients with rheumatic disease identify a family of three immunologically related polypeptides that we have designated CENP-A (17 kDa), CENP-B (80 kDa), and CENP-C (140 kDa). CENP-B has been cloned and sequenced. DNA sequence analysis indicates that this polypeptide possesses two large regions with extraordinary concentrations of acidic residues (region I: 61 residues with 79% glu + asp; region II: 31 residues with 87% glu + asp). Despite this concentration of negative charge, immunocytochemical experiments suggest that CENP-B may be a DNA binding protein. In these experiments, the levels of CENP-B are seen to vary reproducibly from chromosome to chromosome. The role of CENP-B in vivo is unknown. However, it is unlikely to bind directly to the spindle microtubules since it is found at an inactive centromere that apparently does not attach to the spindle. (ii) Components of the inner centromere: we have injected mice with the whole chromosome scaffold fraction to elicit production of monoclonal antibodies. One such antibody identifies two structurally related polypeptides (the INCENP antigens, 135 and 155 kDa) that are preferentially located between the sister chromatids at the centromere. The INCENP antigens undergo dramatic movements from the chromosomes to the central spindle during mitosis. They are ultimately sequestered in the midbody and discarded. Several lines of evidence suggest that the INCENP polypeptides may be involved in the regulation of sister chromatid separation at the metaphase-anaphase transition. 相似文献
5.
The postsynaptic density (PSD) is a cytoskeletal specialization within the postsynaptic membrane of a neuron that helps to concentrate and organize neurotransmitter receptors at a chemical synapse. The total number of receptors within the PSD, which is a major factor in determining the physiological strength or weight of a synapse, fluctuates due to the surface diffusion of receptors into and out of the PSD, and the interactions of receptors with scaffolding proteins and cytoskeletal elements within the PSD. In this article, we present a stochastic model of protein receptor trafficking at the PSD that takes into account these various processes. The PSD is treated as a stochastically gated corral, which contributes a source of extrinsic or environmental noise that supplements the intrinsic noise arising from small receptor numbers. Using a combination of stochastic analysis and Monte Carlo simulations, we determine the time-dependent variation in the mean and variance of synaptic receptor numbers for a variety of initial conditions that simulate fluorescence recovery after photobleaching experiments, and indicate how such data might be used to infer certain properties of the PSD. 相似文献
6.
The methods are given which were used to determine the number of stages in the life history of Trichoniscus pusillus pusillus Brandt, 1833 and the stages are described as far as possible. Not all stadia can be separated on morphological grounds and animals extracted from monthly litter samples were measured and the stadia separated by use of probability paper. This method proved quite successful and confirmed the characterization of the three earlier juvenile stadia on morpholigical grounds and the number of the later juvenile stadia determined from laboratory cultures. There are six juvenile and five adult stadia. 相似文献
7.
Homology of Saccharomyces cerevisiae ADH4 to an iron-activated alcohol dehydrogenase from Zymomonas mobilis 总被引:8,自引:0,他引:8
Summary Insertion of the transposable element Ty at the ADH4 locus results in increased levels of a new alcohol dehydrogenase (ADH) activity in Saccharomyces cerevisiae. The DNA sequence of this locus has been determined. It contains a long open reading frame which is not homologous to the other ADH isozymes that have been characterized in S. cerevisiae nor does it show obvious homology to Drosophila ADH. The hypothetical ADH does, however, show strong homology to the sequence of an iron-activated ADH from the bacterium Zymomonas mobilis. Thus ADH4 appears to encode an ADH structural gene which, along with the Zymomonas enzyme, may define a new family of alcohol dehydrogenases.Now The Plant Cell Research Institute, Inc., 6560 Trinity Court, Dublin, CA 94568, USA 相似文献
8.
Altitudinal changes in the incidence of crassulacean acid metabolism in vascular epiphytes and related life forms in Papua New Guinea 总被引:1,自引:0,他引:1
M. J. Earnshaw K. Winter H. Ziegler W. Stichler N. E. G. Cruttwell K. Kerenga P. J. Cribb J. Wood J. R. Croft K. A. Carver T. C. Gunn 《Oecologia》1987,73(4):566-572
Summary The occurrence of Crassulacean acid metabolism (CAM), as judged from 13C values, was investigated in epiphytes and some related plant species at a series of sites covering the approximate altitudinal range of epiphytes in Papua New Guinea. Comprehensive collections were made at each site and the occurrence of water storage tissue and blade thickness was also determined. Some 26% of epiphytic orchids from a lowland rainforest (2–300 m.a.s.l) showed 13C values typical of obligate CAM and possessed leaves thicker than 1 mm. A second group of orchids, mostly with succulent leaves, possessed intermediate 13C values between -23 and -26% and accounted for 25% of the total species number. Some species of this group may exhibit weak CAM or be facultative CAM plants. The remainder of the lowland rainforest species appeared to be C3 plants with 13C values between -28 and -35%. and generally possessed thin leaves. Obligate CAM species of orchids from a lower montane rainforest (1175 m.a.s.l) comprised 26% of the species total and mostly possessed thick leaves. The remainder of the species were generally thin-leaved with 13C values between -26 and -35%. largely indicative of C3 photosynthesis. Orchids with intermediate 13C values were not found in the lower montane rainforest. Obligate CAM appeared to be lacking in highland epiphytes from an upper montane rainforest and subalpine rainforest (2600–3600 m.a.s.l). However the fern, Microsorium cromwellii had a 13C value of -21.28%. suggesting some measure of CAM activity. Other highland ferns and orchids showed more negative °13C values, up to-33%., typical of C3 photosynthesis. The highland epiphytic orchids possessed a greater mean leaf thickness than their lowland C3 counterparts due to the frequent occurrence of water storage tissue located on the adaxial side of the leaf. It is suggested that low daytime temperatures in the highland microhabitats is a major factor in explaining the absence of CAM. The increased frequency of water storage tissue in highland epiphytes may be an adaptation to periodic water stress events in the dry season and/or an adaptation to increased levels of UV light in the tropicalpine environment. 相似文献
9.
Control of wild carrot somatic embryo development by antioxidants : a probable mode of action of 2,4-dichlorophenoxyacetic Acid 总被引:1,自引:0,他引:1
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As we previously reported for glutathione (GSH), both ascorbic acid (AA) and vitamin E were observed to suppress wild carrot (Daucus carota L.) somatic embryogenesis with little concomitant effect on biomass. Endogenous concentrations of AA were lower during embryo development than during cell proliferation, exhibiting a temporal pattern nearly identical to that of GSH. GSSG (oxidized GSH) reductase was found to be considerably more active in proliferating than in developing cultures, whereas no difference was evident in the case of dehydroascorbate (DHA) reductase. Both GSH and AA concentrations in these cells are governed by 2,4-D. These results show that redox status is a strong determinant of proliferative versus developmental growth and indicate that the mode of action of 2,4-D in this system may be explained at least in part by its influence on endogenous antioxidant levels. 相似文献
10.
Vertical distributions and relations of euphausiid populations off Elephant Island,March 1984 总被引:4,自引:3,他引:1
Summary Distributional relationships are described for post-larval and larval Euphausia superba and Thysanoessa sp. (probably macrura) and post-larval Euphausia frigida collected in 0–70/80 m and 0–175/200 m depth ranges with a MOCNESS sampler north of Elephant Island (61°S, 55°W) during 17–23 March 1984. Larval E. superba (predominantly calyptopes stage 2 and 3) were rare shallower than 80 m at night. Day catches of post-larval E. suberba were small and night catches were primarily near the top of the thermocline above 50 m depth. Thysanoessa sp. occurred throughout the 0–200 m depth range and was abundant in the upper 80 m both night and day. E. frigida migrated to the upper 80 m at night from deeper day depths. Larval stages of E. superba and bost-larval stages of all three species demonstrated independent and variable vertical distribution patterns both night and day. Changes in E. superba abundance and distributional patterns could to a certain extent be associated with observed environmental changes. An increase in larval and decrease in post-larval E. superba abundances between 0–80 m was associated with an intrusion of cold water at depth. At night, vertically restricted concentrations of post-larval E. superba were associated with shallow mixed layer depths, and a significant vertical separation of developmental stages and size categories was observed only during periods of stratification in the upper 80 m. Fluctuations in the distribution and abundance of Thysanoessa sp. and distribution of E. frigida did not appear to be influenced by physical parameters within the upper 80 m. Within the 0–80 m depth range, the distributions of these two species differed from each other and from E. superba and showed large tow to tow variability that could not be related to physical parameters in the upper water column. 相似文献