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31.
ARTURO ARGÜELLO RUTH DEL PRADO PALOMA CUBAS ANA CRESPO 《Biological journal of the Linnean Society. Linnean Society of London》2007,91(3):455-467
Morphological and phylogenetic relationships of the worldwide Mediterranean lichen forming fungus, Parmelina quercina , have been studied. Specimens from western Europe, western North America and southern Australia were analysed using molecular data (nuITS rDNA, nuLSU rDNA and mtSSU rDNA) and selected morphological features (upper cortex maculae, scanning electron microscopy examination of the epicortex, ascospores and conidia shape and size, and amphithecial retrorse rhizines). The results conclusively reveal that: (1) there is not one single species but four separate species in the Mediterranean or sub Mediterranean areas of the world. Parmelina quercina and Parmelina carporrhizans (Euroasiatic species), Parmelina coleae sp. nov. (North America) and Parmelina elixia sp. nov. (Australia); (2) largely debated P. carporrhizans is not a synonym of P. quercina but supported as a valid species circumscribed to Macaronesic relict sites; (3) the geographical isolation of the Australian population is correlated with a large genetic distance; (4) morphological characters (ascospores and conidial variability and thallus epicortex) correlate with the phylogenetic hypothesis; (5) the new or revalidated species within Parmelina quercina are not cryptic species but morphologically recognizable taxa. © 2007 The Linnean Society of London, Biological Journal of the Linnean Society , 2007, 91 , 455–467. 相似文献
32.
RUTH EICHMANN CORNELIA DECHERT KARL-HEINZ KOGEL RALPH HÜCKELHOVEN 《Molecular Plant Pathology》2006,7(6):543-552
BAX Inhibitor-1 (BI-1) is a conserved cell death suppressor protein. In barley, BI-1 ( HvBI-1 ) expression is induced upon powdery mildew infection and when over-expressed in epidermal cells of barley, HvBI-1 induces susceptibility to the biotrophic fungal pathogen Blumeria graminis . We co-expressed mammalian pro-apoptotic BAX together with HvBI-1, and the mammalian BAX antagonist BCL-XL in barley epidermal cells. BAX expression led to cessation of cytoplasmic streaming and collapse of the cytoplasm while co-expression of HvBI-1 and BCL-XL partially or completely, respectively, rescued cells from BAX lethality. When B. graminis was attacking epidermal cells, a green fluorescent protein fusion of HvBI-1 accumulated at the site of attempted penetration and was also present around haustoria. Over-expression of HvBI-1 in epidermal cells weakened a cell-wall-associated local hydrogen peroxide burst in a resistant mlo -mutant genotype and supported haustoria accommodation in race-specifically resistant MLA12 -barley. HvBI-1 is a cell death regulator protein of barley with the potential to suppress host defence reactions. 相似文献
33.
JOSEPH D. CONROY WILLIAM J. EDWARDS RUTH A. PONTIUS DOUGLAS D. KANE HONGYAN ZHANG JOHN F. SHEA JULIE N. RICHEY DAVID A. CULVER 《Freshwater Biology》2005,50(7):1146-1162
1. Recent increases in phytoplankton biomass and the recurrence of cyanobacterial blooms in western Lake Erie, concomitant with a shift from a community dominated by zebra mussels (Dreissena polymorpha) to one dominated by quagga mussels (D. bugensis), led us to test for differences in ammonia‐nitrogen and phosphate‐phosphorus excretion rates of these two species of invasive molluscs. 2. We found significant differences in excretion rate both between size classes within a taxon and between taxa, with zebra mussels generally having greater nutrient excretion rates than quagga mussels. Combining measured excretion rates with measurements of mussel soft‐tissue dry weight and shell length, we developed nutrient excretion equations allowing estimation of nutrient excretion by dreissenids. 3. Comparing dreissenid ammonia and phosphate excretion with that of the crustacean zooplankton, we demonstrated that the mussels add to nitrogen and phosphorus remineralisation, shortening nitrogen and phosphorus turnover times, and, importantly, modify the nitrogen and phosphorus cycles in Lake Erie. The increased nutrient flux from dreissenids may facilitate phytoplankton growth and cyanobacterial blooms in well‐mixed and/or shallow areas of western Lake Erie. 相似文献
34.
JEFF A. JOHNSON† RUTH E. TINGAY‡ MELANIE CULVER§ FRANK HAILER¶ MICHÈLE L. CLARKE†† DAVID P. MINDELL‡‡ 《Molecular ecology》2009,18(1):54-63
The critically endangered Madagascar fish-eagle ( Haliaeetus vociferoides ) is considered to be one of the rarest birds of prey globally and at significant risk of extinction. In the most recent census, only 222 adult individuals were recorded with an estimated total breeding population of no more than 100–120 pairs. Here, levels of Madagascar fish-eagle population genetic diversity based on 47 microsatellite loci were compared with its sister species, the African fish-eagle ( Haliaeetus vocifer ), and 16 of these loci were also characterized in the white-tailed eagle ( Haliaeetus albicilla ) and the bald eagle ( Haliaeetus leucocephalus ). Overall, extremely low genetic diversity was observed in the Madagascar fish-eagle compared to other surveyed Haliaeetus species. Determining whether this low diversity is the result of a recent bottleneck or a more historic event has important implications for their conservation. Using a Bayesian coalescent-based method, we show that Madagascar fish-eagles have maintained a small effective population size for hundreds to thousands of years and that its low level of neutral genetic diversity is not the result of a recent bottleneck. Therefore, efforts made to prevent Madagascar fish-eagle extinction should place high priority on maintenance of habitat requirements and reducing direct and indirect human persecution. Given the current rate of deforestation in Madagascar, we further recommend that the population be expanded to occupy a larger geographical distribution. This will help the population persist when exposed to stochastic factors (e.g. climate and disease) that may threaten a species consisting of only 200 adult individuals while inhabiting a rapidly changing landscape. 相似文献
35.
SYNOPSIS. An ultrastructural investigation has been carried out on 180°-rotated ciliary meridians (inverted meridians) in Tetrahymena pyriformis temperature-sensitive mutant (molb/molb), syngen 1, strain B. The longitudinal, transverse and postciliary microtubular bands, the kinetodesmal fiber, and the parasomal sac, are shown to be disposed at a 180° angle to their normal positions or orientations. Other abnormalities are as folows: the first 2 basal bodies of the inverted meridian fail to organize into “couplets” and the inverted meridian intrudes into the anterior pole region; an extra longitudinal microtubular band is found in one of the cell lines. 相似文献
36.
A protein, which consists of a defined sequence of amino-acids, can be converted into another protein of equal length by changes in the sequence of nucleotides in the segment of DNA by which it is coded. It is convenient to term this segment a gene. Most proteins are 200–400 amino-acids long, so that most genes, if defined in this way, are represented by 600–1,200, or about 103, nucleotides. The evolution of protein molecules may appear to be limited by the need for each step in the sequence to be at a selective advantage. Maynard Smith1 has compared this with a word game in which, using exclusively meaningful words, one word has to be changed to another by altering one letter at a time. 相似文献
37.
38.
ANTONIANA KRETTLI DAVID H. CHEN RUTH S. NUSSENZWEIG 《The Journal of eukaryotic microbiology》1973,20(5):662-665
Sporozoites of rodent and simian malaria (Plasmodium berghei and P. cynomolgi) were purified by centrifugation on a linear Renografin/BSA gradient. This procedure made it possible to process rapidly a large number of infected mosquitoes leading to the recovery of a considerable proportion of sporozoites. Gradient-recovered sporozoites (GRS) freed of most bacteria and mosquito tissue contaminants, retained their infectivity and immunogenicity. Mice repeatedly injected i.v. with irradiated GRS of P. berghei acquired total protection against an otherwise lethal sporozoite challenge. GRS of P. berghei and P. cynomolgi induced antisporozoite (CSP) antibody production in rats. 相似文献
39.
SUMMARY: Ignoring wasted material at the surface and sides, the variation in pH in six months old pit silage was smaller from side to side than from top to bottom. At the 2-foot level, where the best quality silage was found, variation was very slight. A correlation was found between pH and the logarithm of the microscopical count of bacteria, the total number of bacteria falling with decreasing pH. 相似文献
40.