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1.
Potassium Transport in Enteromorpha intestinalis (L.) Link: II. EFFECTS OF MEDIUM COMPOSITION AND METABOLIC INHIBITORS 总被引:2,自引:0,他引:2
In springwater (25.5 mol m3 Cl, 20.4 mol m3Na+, 0.14 mol m3 K+) Enteromorpha intestinalis couldnot survive for more than a few weeks unless provided with 0.5mol m3 K+ in the medium or alternatively exposed to seawaterfor 1 day per week. Maintenance of a cytoplasmic K+ level ofabout 200 mol m3 is critical for the maintenance of normalmetabolic activity. Net gains of intracellular K+ occurred whenthe plants were transferred from low-salinity to seawater; converselylarge net losses occurred when plants were transferred fromseawater to springwater. These two processes were not simplythe reverse of one another; net gain of K+ involved a largeincrease in the tracer flux both into and out of the cell butnet loss of K+ virtually halted the tracer flux into the cell.Any injury incurred by rapid salinity changes was short-lived;plants were rapidly able to adjust intracellular [K1.K+). K+(orto some extent Rb+) was found to be necessary in the effluxmedium for 42K+ exchange to occur. The osmotic concentrationof the medium was also important but extracellular Na+ and Clconcentrationswere not critical. K+ influx and efflux in both springwaterand seawater were largely independent of light and were sensitivein varying degrees to a range of common metabolic inhibitorsand uncouplers. The results are best explained by the presenceof an active K+ influx, generated by an ATP-dependent K+ pumpat the plasmalemma. Key words: Enteromorpha, Potassium transport, Salinity changes, Uncouplers, Inhibitors 相似文献
2.
SODIUM TRANSPORT IN ENTEROMORPHA INTESTINALIS (L.) LINK 总被引:1,自引:1,他引:0
3.
The permeability (P) of a lipophilic cation, triphenylmethylphosphonium(TPMP+) which is frequently used as a membrane potential probe,has been measured in Chara australis (Charophyceae). PTPMP+across biological membranes is usually thought to be very highbut this is not the case across the plasmalemma of Chara. Thepermeability of TPMP+ across the plasmalemma was found to betypical of inorganic cations, about 1.0 nm s1. Estimateswere made of the permeability of lipophilic cations across someother cell membranes, based on previously published work. Thepermeability of TPMP+ across the plasma membranes of the redalga, Griffithsia monilis and the blue-green alga, Anabaenavariabilis was about 25 nm s1. The permeabilityof TPMP+ across the plasma membranes of eukaryotes and prokaryotesappears to be similar. The permeability of lipophilic cationsacross the cristae of isolated mitochondria are exceptionallyhigh, about 170 nm s1. TPMP+ did not behave as a thiamineanalogue in Chara, unlike in the case of yeast. The means ofentry of TPMP+ into the Chara cell, driven by the electrochemicalgradient across the plasmalemma, has not been identified. Thepresence of a second lipophilic cation probe, DDA+ (dibenzyldimethylammonium),caused a decrease in the uptake flux of TPMP+; this suggeststhat the two lipophilic cations compete for the same site atthe surface of the plasmalemma. Key words: Chara australis, TPMP+, Permeability, Lipophilic cation 相似文献
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The cyanobacterium Synechococcus R-2 (Anacystis nidulans, S. leopoliensis) PCC 7942 has a sodium-dependent chloride transporter 总被引:1,自引:1,他引:0
R. J. RITCHIE 《Plant, cell & environment》1992,15(2):163-177
Synechococcus R-2 (PCC 7942) actively accumulated Cl? in the light and dark, under control conditions (BG-11 media: pHo, 7·5; [Na+]o, 18 mol m?3; [Cl?]o, 0·508 molm?3). In BG-11 medium [Cl?], was 17·2±0·848 mol m?3 (light), electrochemical potential of Cl? (ΔμCl?i,o) =+211±2mV; [Cl?]i= 1·24±0·11 mol m?3(dark), ΔμCl?i,o=+133±4mV. Cl? fluxes, but not permeabilities, were much higher in the light: ?Cl?i,o= 4·01±5·4 nmol m?2 s?1, PCl?i,o= 47±5pm s?1 (light); ?Cl?i,o= 0·395±0·071 nmol m?2 s?1, PCl?i,o= 69±14 pm s?1 (dark). Chloride fluxes are inhibited by acid pHo (pHo 5; ?Cl?i,o= 0·14±0·04 nmol m?2 s?1); optimal at pHo 7·5 and not strongly inhibited by alkaline pHo (pHo 10; ?Cl?1i,o= 1·7±0·14 nmol m?2 s?1). A Cl?in/2H+in coporter could not account for the accumulation of Cl? alkaline pHo. Permeability of Cl? is very low, below 100pm s?1 under all conditions used, and appears to be maximal at pHo 7·5 (50–70 pm s?1) and minimal in acid pHo (20pm s?1). DCCD (dicyclohexyl-carbodiimide) inhibited ?Cl?i,o in the light about 75% and [Cl?]i fell to 2·2±0·26 (4) mol m?3. Valinomycin had no effect but monensin severely inhibited Cl? uptake ([Cl?]i= 1·02±0·32 mol m?3; ?Cl?i,o= 0·20±0·1 nmol m?2 s?1). Vanadate (200 mmol m?3) accelerated the Cl? flux (?Cl?i,o= 5·28±0·64 nmol m?2 s?1) but slightly decreased accumulation of Cl? ([Cl?], = 13·9±1·3 mol m?3) in BG-11 medium but had no significant effect in Na+-free media. DCMU (dichlorophenyldimethylurea) did not reduce [Cl?], or ?Cl?i,o to that found in the dark ([Cl?]i= 8·41±0·76 mol m?3; ?Cl?i,o= 2·06±0·36 nmol m?2 s?1). Synechococcus also actively accumulated Cl? in Na+-free media, [Cl?]i was lower but ΔΨi,o hyperpolarized in Na+-free media and so the ΔμCl?i,o was little changed ([Cl?]i= 7·98±0·698 mol m?3; ΔμCl?i,o=+203±3 mV). Net Cl? uptake was stimulated by Na+; Li+ acted as a partial analogue for Na+. Synechococcus has a Na+ activated Cl? transporter which is probably a primary 2Cl?/ATP pump. The Cl? pump is voltage sensitive. ΔμCl?i,o is directly proportional to ΔΨi,o(P»0·01%): ΔμCl?i,o= -1·487 (±0·102) ×ΔΨi,o, r= -0·983, n= 31. The ΔμCl?i,o increased (more positive) as the Δμi,o became more negative. The ΔμCl?i,o has no known function, but might provide a driving force for the uptake of micronutrients. 相似文献
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7.
M. A. SCHÄFER D. MAZZI K. KLAPPERT H. KAURANEN J. VIEIRA A. HOIKKALA M. G. RITCHIE C. SCHLÖTTERER 《Journal of evolutionary biology》2010,23(3):518-527
Current advances in genetic analysis are opening up our knowledge of the genetics of species differences, but challenges remain, particularly for out‐bred natural populations. We constructed a microsatellite‐based linkage map for two out‐bred lines of Drosophila montana derived from divergent populations by taking advantage of the Drosophila virilis genome and available cytological maps of both species. Although the placement of markers was quite consistent with cytological predictions, the map indicated large heterogeneity in recombination rates along chromosomes. We also performed a quantitative trait locus (QTL) analysis on a courtship song character (carrier frequency), which differs between populations and is subject to strong sexual selection. Linkage mapping yielded two significant QTLs, which explained 3% and 14% of the variation in carrier frequency, respectively. Interestingly, as in other recent studies of traits which can influence speciation, the strongest QTL mapped to a genomic region partly covered by an inversion polymorphism. 相似文献
8.
Reproductive isolation and the period gene of Drosophila 总被引:2,自引:0,他引:2
The identification of genes of large effect on ecologically important traits is an important aim of molecular ecology. The period gene of Drosophila is a candidate for a gene with a large influence on premating isolation between Drosophila species, as it determines species specific aspects of courtship behaviour. Strains of D. melanogaster are available which have been genetically transformed with the period gene of either D. melanogaster or D. simulans. Here we show that D. melanogaster females do not discriminate between two such strains. This suggests that period may only make a small contribution to total premating isolation between these species. We discuss the use of genetically transformed strains in assessing the influence of single genes on complex traits. 相似文献
9.
The role of methane as a greenhouse gas and the contribution of bacteria to the production (methanogenesis) and destruction (methane oxidation) of methane is described. Using experimental approaches based on DNA sequences identifying either methanogen-specific or methanotroph-specific gene sequences methods were developed to broaden the detection and identification of methane metabolizing bacteria in natural environments. These methods were focused on blanket bog peat but are suitable for other environments. In addition to group specific 16S rRNA DNA sequences, specific functional gene probes based on methane coenzyme reductase sequences for methanogens and methane monooxygenase sequences for methanotrophs, were developed. These sequences were used in PCR-based protocols to detect and amplify specific gene sequences from the total DNA isolated from transverse sections of blanket bog peat. This permitted the analysis of the vertical distribution of methanogen and methanotroph populations, discrimination between different sub-sets of these populations, and the identification of novel organisms not previously detected by culture-based methods. 相似文献
10.
CHLORIDE TRANSPORT IN ENTEROMORPHA INTESTINALIS (L.) LINK 总被引:2,自引:2,他引:0