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71.
Genetic variation within and between vegetative compatibility groups (VCGs) of Amylostereum areolatum (Fr.) Boid. and Amylostereum chailletii (Pers.: Fr.) Boid. isolates was investigated. DNA fingerprints were made using the M13 core sequence as a primer. A total of 53 isolates of A. areolatum and 57 isolates of A. chailletii from Lithuania, Sweden, Denmark and Great Britain were studied. In all cases isolates belonging to the same VCG showed identical DNA banding patterns, suggesting that VCGs correspond to clones. In A. areolatum the vast majority of the isolates (spread by Sirex juvencus L.) were assigned to dispersive clones, that have wide geographical distribution (i.e. the same genotypes were detected in Lithuania, Sweden and Denmark), with low genetic variation between the different clones. By contrast, A. chailletii population structure was consistent with the spread of airborne basidiospores produced by outcrossing. Only a small fraction of A. chailletii isolates studied, could be assigned to dispersal clones with a local distribution, spread by Urocerus gigas L. Overall, M13 fingerprinting detected low genetic differentiation in both species in the samples we studied. 相似文献
72.
CHARACTERISTIC patterns resembling those revealed by the fluorochrome techniques1 appear along human mitotic metaphase chromosomes when methanol-acetic acid-fixed preparations are heated to 69° C and stained with Giemsa solution. This procedure is a greatly simplified version of one developed by F. E. Arrighi and T. C. Hsu (personal communication) which heavily stains the centromere regions and produces distinct patterns on the chromosome arms. We chose the conditions for pretreatment of the preparations on the basis of the finding of Marmur and Doty2 that the transition temperature, that is, the temperature at which the double helical configuration of DNA changes to a disordered coiling, for adenine-thymine nucleotide pairs, is 69° C. For cytosine-guanine pairs they found that the transition temperature is 110° C. Heating to the lower transition temperature should therefore denature regions of DNA rich in adenine-thymine pairs, leaving regions rich in cytosine-guanine pairs intact; such differences might be reflected in the staining properties, although the differential staining that occurs after heat treatment is obviously open to alternative interpretations. 相似文献
73.
FRANS WITTE MONIQUE WELTEN MARTIN HEEMSKERK IRENE VAN DER STAP LISANNE HAM HENDRIKUS RUTJES JAN WANINK 《Biological journal of the Linnean Society. Linnean Society of London》2008,94(1):41-52
During the upsurge of the introduced predatory Nile perch in Lake Victoria in the 1980s, the zooplanktivorous Haplochromis ( Yssichromis ) pyrrhocephalus nearly vanished. The species recovered coincident with the intense fishing of Nile perch in the 1990s, when water clarity and dissolved oxygen levels had decreased dramatically due to increased eutrophication. In response to the hypoxic conditions, total gill surface in resurgent H. pyrrhocephalus increased by 64%. Remarkably, head length, eye length, and head volume decreased in size, whereas cheek depth increased. Reductions in eye size and depth of the rostral part of the musculus sternohyoideus, and reallocation of space between the opercular and suspensorial compartments of the head may have permitted accommodation of larger gills in a smaller head. By contrast, the musculus levator posterior, located dorsal to the gills, increased in depth. This probably reflects an adaptive response to the larger and tougher prey types in the diet of resurgent H. pyrrhocephalus . These striking morphological changes over a time span of only two decades could be the combined result of phenotypic plasticity and genetic change and may have fostered recovery of this species. © 2008 The Linnean Society of London, Biological Journal of the Linnean Society , 2008, 94 , 41–52. 相似文献
74.
INA FRANZN BERNARD SLIPPERS RIMVYDAS VASILIAUSKAS JAN STENLID 《Molecular ecology resources》2006,6(3):870-872
Seven polymorphic microsatellite markers were developed for the wood‐decay basidiomycete Phlebia centrifuga. The primers were identified using two techniques, based on intersimple sequence repeats (ISSR) and amplified fragment length polymorphism (AFLP), respectively. The markers were screened on 27 isolates from Europe and North America. Two markers varied only on a worldwide scale, but not within Europe. The other five showed variation on both scales. These markers will now be used to characterize populations of P. centrifuga, which is red‐listed as near‐threatened in its natural habitat due to human disturbance. 相似文献
75.
1. High water column NO3? concentrations, low light availability and anoxic, muddy sediments are hypothesised to be key factors hampering growth of rooted submerged plants in shallow, eutrophic fresh water systems. In this study, the relative roles and interacting effects of these potential stressors on survival, growth, allocation of biomass and foliar nutrient concentrations of Potamogeton alpinus were determined in a mesocosm experiment using contrasting values of each factor (500 versus 0 μmol L?1 NO3?; low irradiance, corresponding to the eutrophic environment, versus ambient irradiance; and muddy versus sandy sediment). 2. Low irradiance, high NO3? and sandy sediment led to reduced growth. In a muddy sediment, plants had lower root : shoot ratios than in a sandy sediment. 3. Growth at high NO3? and on the sandy sediment resulted in lower foliar N and C concentrations than in the contrasting treatments. The C : N ratio was higher at high NO3? and on the sandy sediment. Foliar P was higher on the muddy than on the sandy sediment but was not affected by irradiance or NO3?. The N : P ratio was lowest at high NO3? on the sandy sediment. 4. Total foliar free amino acid concentration was lowest on sand, low irradiance and high NO3?. Total free amino acid concentration and growth were not correlated. 5. Turbidity and ortho‐PO43? concentration of the water layer were lower at high water column NO3? indicating that the growth reduction was not associated with increased algal growth but that physiological mechanisms were involved. 6. We conclude that high water column NO3? concentrations can significantly reduce the growth of ammonium preferring rooted submerged species such as P. alpinus, particularly on sediments with a relatively low nutrient availability. Further experiments are needed to assess potential negative effects on other species and to further elucidate the underlying physiological mechanisms. 相似文献
76.
JACQUES F. G. M. MEIS JAN PETER VERHAVE PAUL H. K. JAP ROBERT E. SINDEN JOSEPH H. E. T. MEUWISSEN 《The Journal of eukaryotic microbiology》1983,30(2):361-366
The invasion of liver parenchymal cells by sporozoites of Plasmodium berghei Vincke & Lips, 1948, was studied in vivo using transmission electron microscopy. Livers of Brown Norway rats were examined 30 and 60 min after intraportal injection of 15 million sporozoites each. Sporozoites found after incorporation into vacuoles in hepatocytes were often located near a bile canaliculus at the lateral cell surface, surrounded by hepatocyte lysosomal structures; however, degradation of sporozoites caused by lysosomal digestion inside hepatocytes was never observed. Due to the crescent shape of sporozoites, serial sections were necessary to demonstrate the actual process of invasion of the hepatocyte. The hepatocyte's plasmalemma appeared to invaginate due to the sporozoite's action, thereby creating a parasitophorous vacuole. It was suggested that the sporozoite actively penetrated the hepatocyte; however, no visible depletion of rhoptries and micronemes was observed. 相似文献
77.
The rate of decarboxylation of DL-tryptophan-carboxyl-14C in homogenates of cotyledons, hypocotyls and roots of sterile and non-sterile cucumber seedlings of 4, 8 and 11 days was measured. Tryptophan decarboxylating activity is highest in hypocotyls, lowest in cotyledons. In all organs the activity decreases with age. This enzyme activity does not parallel the IAA level in the organs during ageing. 相似文献
78.
BORIS BÖRSTLER ODILE THIÉRY ZUZANA SÝKOROVÁ ALFRED BERNER DIRK REDECKER 《Molecular ecology》2010,19(7):1497-1511
Glomus intraradices, an arbuscular mycorrhizal fungus (AMF), is frequently found in a surprisingly wide range of ecosystems all over the world. It is used as model organism for AMF and its genome is being sequenced. Despite the ecological importance of AMF, little has been known about their population structure, because no adequate molecular markers have been available. In the present study we analyse for the first time the intraspecific genetic structure of an AMF directly from colonized roots in the field. A recently developed PCR‐RFLP approach for the mitochondrial rRNA large subunit gene (mtLSU) of these obligate symbionts was used and complemented by sequencing and primers specific for a particularly frequent mtLSU haplotype. We analysed root samples from two agricultural field experiments in Switzerland and two semi‐natural grasslands in France and Switzerland. RFLP type composition of G. intraradices (phylogroup GLOM A‐1) differed strongly between agricultural and semi‐natural sites and the G. intraradices populations of the two agricultural sites were significantly differentiated. RFLP type richness was higher in the agricultural sites compared with the grasslands. Detailed sequence analyses which resolved multiple sequence haplotypes within some RFLP types even revealed that there was no overlap of haplotypes among any of the study sites except between the two grasslands. Our results demonstrate a surprisingly high differentiation among semi‐natural and agricultural field sites for G. intraradices. These findings will have major implications on our views of processes of adaptation and specialization in these plant/fungus associations. 相似文献
79.
DAVID S. PORTNOY JAN R. MCDOWELL EDWARD J. HEIST JOHN A. MUSICK JOHN E. GRAVES 《Molecular ecology》2010,19(10):1994-2010
The sandbar shark, Carcharhinus plumbeus, is a large, cosmopolitan, coastal species. Females are thought to show philopatry to nursery grounds while males potentially migrate long distances, creating an opportunity for male‐mediated gene flow that may lead to discordance in patterns revealed by mitochondrial DNA (mtDNA) and nuclear markers. While this dynamic has been investigated in elasmobranchs over small spatial scales, it has not been examined at a global level. We examined patterns of historical phylogeography and contemporary gene flow by genotyping 329 individuals from nine locations throughout the species’ range at eight nuclear microsatellite markers and sequencing the complete mtDNA control region. Pairwise comparisons often resulted in fixation indices and divergence estimates of greater magnitude using mtDNA sequence data than microsatellite data. In addition, multiple methods of estimation suggested fewer populations based on microsatellite loci than on mtDNA sequence data. Coalescent analyses suggest divergence and restricted migration among Hawaii, Taiwan, eastern and western Australia using mtDNA sequence data and no divergence and high migration rates, between Taiwan and both Australian sites using microsatellite data. Evidence of secondary contact was detected between several localities and appears to be discreet in time rather than continuous. Collectively, these data suggest complex spatial/temporal relationships between shark populations that may feature pulses of female dispersal and more continuous male‐mediated gene flow. 相似文献
80.
JIN TAO GUO KATE WEATHERBY DEE CARTER JAN ŠLAPETA 《The Journal of eukaryotic microbiology》2010,57(5):444-446
ABSTRACT. Chromera velia (Chromerida: Alveolata) is a photosynthetic, unicellular organism closely related to parasitic apicomplexa. Diurnal rhythmicity of an immotile–motile transformation has been observed but its role in the life cycle remains largely unknown. Using a multiwell system, we show that salinity and f‐medium concentration significantly affect the percentage of motile C. velia cells. An inverse relationship between salinity and motility in C. velia occurred, and flagellation was also suppressed at high nutrient levels. These results suggest a low salinity environment with relatively low nutrient levels enables flagellate transformation during the diurnal cycle of C. velia. 相似文献