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71.
72.
Wingfield BD; Grant WS; Wolfaardt JF; Wingfield MJ 《Molecular biology and evolution》1994,11(3):376-383
The genus Ceratocystis sensu stricto includes important fungal pathogens of
woody and herbaceous plants. This genus is distinguished from species in
Ceratocystis sensu lato by the presence of Chalara anamorphs. Ascospore
shape has been used extensively in delineating Ceratocystis taxa, which
show a large variety of ascospore shapes. Sequence analysis of one region
of he 18S ribosomal RNA subunit and two regions of the 28S ribosomal RNA
subunit showed that there was a majority of multiple substitutions at
nucleotide sites and that there was a low transition/transversion ratio, T
= 0.72. Both of these results suggest that these are well established, old
species. Ascospore morphology, for the most part, was not congruent with
the molecular phylogeny, and the use of morphological characters may be
misleading in the taxonomy of these species.
相似文献
73.
Ganglioside synthesis and transport to myelin was studied in brainstem slices prepared from 19-21-day-old rats. The slices were incubated for up to 2 h in the presence of [3H]glucosamine to label primarily the hexosamine portion of complex gangliosides. The amount of radioactivity incorporated into gangliosides during slice incubations was only 10-15% of the amount of the label incorporated during in vivo labeling of brainstem gangliosides using equivalent amounts of [3H]glucosamine. Among individual gangliosides this inhibition was greater for the more complex gangliosides. When labeled gangliosides were isolated from homogenate and myelin fractions prepared from brain slices, the complex total gangliosides of both fractions showed a lag in labeling kinetics but with a lower specific radioactivity for the myelin fraction, reflecting the larger pool size and slower turnover rate exhibited by myelin components. Chase experiments showed that more complex gangliosides in homogenate exhibited almost no effect of chase after 30 min. Addition of the Golgi-disrupting agent monensin to slice incubations inhibited the labeling of all gangliosides except GM3, GM2, and GD3, and transport to myelin of all complex gangliosides except GM2. These results show that a monensin-sensitive mode of transport is responsible for the translocation of most newly synthesized gangliosides into myelin. 相似文献
74.
MJ Doughty 《Biotechnic & histochemistry》2016,91(8):501-509
Goblet cells were visualized in impression cytology specimens from bulbar conjunctiva of the rabbit eye using Giemsa staining. Highly magnified images were used to generate outlines of the goblet cells and their characteristic eccentric nuclei. Using sets of 10 cells from 15 cytology specimens, I found that the longest dimension of the goblet cells averaged 16.7 ± 2.3 μm, the shortest dimension averaged 14.4 ± 1.8 μm and the nucleus averaged 6.3 ± 0.8 μm. The goblet cells were ellipsoid in shape and the longest:shortest cell dimension ratio averaged 1.169 ± 0.091. The goblet cell areas ranged from 108 to 338 μm2 (average 193 ± 50 μm2). The area could be predicted reliably from the longest and shortest dimensions (r2 = 0.903). The areas of goblet cell nuclei were 15–58 μm2 (average 33 ± μm2) and the nucleus:cytoplasm area fraction was predictably greater in smaller goblet cells and less in the larger goblet cells (Spearman correlation = 0.817). The nuclei were estimated to occupy an average of 9.5% of the cell volume. The differences in size, shape and nucleus:cytoplasm ratio may reflect differences in goblet cell maturation. 相似文献
75.
76.
Steven K. Schmidt Andrew J. King Courtney L. Meier William D. Bowman Emily C. Farrer Katharine N. Suding 《Plant Ecology & Diversity》2015,8(5-6):703-712
Here we review the numerous studies of plant–microbe interactions conducted at the Niwot Ridge LTER site in Colorado, USA. By synthesising work at scales ranging from the rhizosphere to the landscape, we offer a mechanistic view of how these interactions are essential to understanding the spatial and temporal structuring of plant and microbial communities across this diverse and changing landscape. These new insights are also important for making predictions about how both plant and microbial communities and populations will respond to future changes in this environment, especially with regard to the potential uphill movement of plants and microbes in response to climate change and nitrogen deposition. We predict that the uphill movement of plants and microbes will be especially apparent, and have the most impact, in areas of the alpine that are now mostly plant free. These areas are currently undergoing a shift from a microbe-dominated ecosystem to one where microbe–plant interactions will play a critical role in reducing nutrient losses to downstream ecosystems. 相似文献
77.
What's in a name; Genetic structure in Solanum section Petota studied using population-genetic tools
Mirjam MJ Jacobs Marinus JM Smulders Ronald G van den Berg Ben Vosman 《BMC evolutionary biology》2011,11(1):42
Background
The taxonomy and systematic relationships among species of Solanum section Petota are complicated and the section seems overclassified. Many of the presumed (sub)species from South America are very similar and they are able to exchange genetic material. We applied a population genetic approach to evaluate support for subgroups within this material, using AFLP data. Our approach is based on the following assumptions: (i) accessions that may exchange genetic material can be analyzed as if they are part of one gene pool, and (ii) genetic differentiation among species is expected to be higher than within species. 相似文献78.
Susan C Burleigh Teun van de Laar Corné JM Stroop Wout MJ van Grunsven Niaobh O’Donoghue Pauline M Rudd Gavin P Davey 《BMC biotechnology》2011,11(1):1-17
Background
The photorespiratory nitrogen cycle in C3 plants involves an extensive diversion of carbon and nitrogen away from the direct pathways of assimilation. The liberated ammonia is re-assimilated, but up to 25% of the carbon may be released into the atmosphere as CO2. Because of the loss of CO2 and high energy costs, there has been considerable interest in attempts to decrease the flux through the cycle in C3 plants. Transgenic tobacco plants were generated that contained the genes gcl and hyi from E. coli encoding glyoxylate carboligase (EC 4.1.1.47) and hydroxypyruvate isomerase (EC 5.3.1.22) respectively, targeted to the peroxisomes. It was presumed that the two enzymes could work together and compete with the aminotransferases that convert glyoxylate to glycine, thus avoiding ammonia production in the photorespiratory nitrogen cycle.Results
When grown in ambient air, but not in elevated CO2, the transgenic tobacco lines had a distinctive phenotype of necrotic lesions on the leaves. Three of the six lines chosen for a detailed study contained single copies of the gcl gene, two contained single copies of both the gcl and hyi genes and one line contained multiple copies of both gcl and hyi genes. The gcl protein was detected in the five transgenic lines containing single copies of the gcl gene but hyi protein was not detected in any of the transgenic lines. The content of soluble amino acids including glycine and serine, was generally increased in the transgenic lines growing in air, when compared to the wild type. The content of soluble sugars, glucose, fructose and sucrose in the shoot was decreased in transgenic lines growing in air, consistent with decreased carbon assimilation.Conclusions
Tobacco plants have been generated that produce bacterial glyoxylate carboligase but not hydroxypyruvate isomerase. The transgenic plants exhibit a stress response when exposed to air, suggesting that some glyoxylate is diverted away from conversion to glycine in a deleterious short-circuit of the photorespiratory nitrogen cycle. This diversion in metabolism gave rise to increased concentrations of amino acids, in particular glutamine and asparagine in the leaves and a decrease of soluble sugars. 相似文献79.
Stoats are significant predators of native fauna in New Zealand. They occur in many habitat types and consume a wide range of prey. The diet of stoats in the Tasman River, South Canterbury, was studied by analysis of scats and den contents. Analysis of 206 scats showed that stoats ate mainly lagomorphs, birds and invertebrates. Minor components included mice, lizards, fish and hedgehogs. Stoats ate more birds in spring than in autumn, and female stoats ate more invertebrates than did males. The contents of 219 dens collected in the same area at the same time provided further information. Birds and lagomorphs occurred at high frequency in dens, and other components were minor. Remains in dens were larger than in scats and allowed identification of many more prey items to species level. Den contents revealed a potentially substantial impact of stoats on threatened shorebirds locally; this impact was not detected by analysis of scats. 相似文献
80.
Can Yang Cong Li Henry R. Kranzler Lindsay A. Farrer Hongyu Zhao Joel Gelernter 《Human genetics》2014,133(5):617-624
Alcohol dependence (AD) is a complex psychiatric disorder that affects about 12.5 % of US adults. Genetic factors play a major role in the development of AD. We conducted a genomewide association study in 2,875 African-Americans including 1,719 AD cases and 1,156 controls. We used the Illumina Omni 1-Quad microarray, which yielded 769,498 single-nucleotide polymorphisms (SNPs) after quality control. To explore the genetic architecture of AD, we estimated the variance that could be explained by all SNPs and subsets of SNPs using two different approaches to genome partitioning. We found that 23.9 % (s.e. 9.3 %) of the phenotypic variance could be explained by using all of the common SNPs on the array. We also found a significant linear relationship between the proportion of the top SNPs used and the phenotypic variance explained by them. Based on genome partitioning of common variants, we also observed a significant linear relationship between the variance explained by a chromosome and its length. Chromosome 4, known to contain several AD risk genes, accounted for excess risk in proportion to its length. By functional partitioning, we found that the genetic variants within 20 kb of genes explained 17.5 % (s.e. 11.4 %) of the phenotypic variance. Our findings are consistent with the generally accepted view that AD is a highly polygenic trait, i.e., the genetic risk in AD appears to be conferred by multiple variants, each of which may have a small or moderate effect. 相似文献