Oceanic phytoplankton species have highly efficient mechanisms of iron acquisition, as they can take up iron from environments in which it is present at subnanomolar concentrations. In eukaryotes, three main models were proposed for iron transport into the cells by first studying the kinetics of iron uptake in different algal species and then, more recently, by using modern biological techniques on the model diatom Phaeodactylum tricornutum. In the first model, the rate of uptake is dependent on the concentration of unchelated Fe species, and is thus limited thermodynamically. Iron is transported by endocytosis after carbonate-dependent binding of Fe(III)' (inorganic soluble ferric species) to phytotransferrin at the cell surface. In this strategy the cells are able to take up iron from very low iron concentration. In an alternative model, kinetically limited for iron acquisition, the extracellular reduction of all iron species (including Fe') is a prerequisite for iron acquisition. This strategy allows the cells to take up iron from a great variety of ferric species. In a third model, hydroxamate siderophores can be transported by endocytosis (dependent on ISIP1) after binding to the FBP1 protein, and iron is released from the siderophores by FRE2-dependent reduction. In prokaryotes, one mechanism of iron uptake is based on the use of siderophores excreted by the cells. Iron-loaded siderophores are transported across the cell outer membrane via a TonB-dependent transporter (TBDT), and are then transported into the cells by an ABC transporter. Open ocean cyanobacteria do not excrete siderophores but can probably use siderophores produced by other organisms. In an alternative model, inorganic ferric species are transported through the outer membrane by TBDT or by porins, and are taken up by the ABC transporter system FutABC. Alternatively, ferric iron of the periplasmic space can be reduced by the alternative respiratory terminal oxidase (ARTO) and the ferrous ions can be transported by divalent metal transporters (FeoB or ZIP). After reoxidation, iron can be taken up by the high-affinity permease Ftr1.

• Klíčová slova
• iron, iron uptake, micro-algae, ocean, phytoplankton,
• Publikační typ
• časopisecké články MeSH
• přehledy MeSH

PII signal transduction proteins are widely spread among all domains of life where they regulate a multitude of carbon and nitrogen metabolism related processes. Non-diazotrophic cyanobacteria can utilize a high variety of organic and inorganic nitrogen sources. In recent years, several physiological studies indicated an involvement of the cyanobacterial PII protein in regulation of ammonium, nitrate/nitrite, and cyanate uptake. However, direct interaction of PII has not been demonstrated so far. In this study, we used biochemical, molecular genetic and physiological approaches to demonstrate that PII regulates all relevant nitrogen uptake systems in Synechocystis sp. strain PCC 6803: PII controls ammonium uptake by interacting with the Amt1 ammonium permease, probably similar to the known regulation of E. coli ammonium permease AmtB by the PII homolog GlnK. We could further clarify that PII mediates the ammonium- and dark-induced inhibition of nitrate uptake by interacting with the NrtC and NrtD subunits of the nitrate/nitrite transporter NrtABCD. We further identified the ABC-type urea transporter UrtABCDE as novel PII target. PII interacts with the UrtE subunit without involving the standard interaction surface of PII interactions. The deregulation of urea uptake in a PII deletion mutant causes ammonium excretion when urea is provided as nitrogen source. Furthermore, the urea hydrolyzing urease enzyme complex appears to be coupled to urea uptake. Overall, this study underlines the great importance of the PII signal transduction protein in the regulation of nitrogen utilization in cyanobacteria.

• Klíčová slova
• ABC transporters, GlnB, PII signaling protein, ammonium uptake, cyanobacteria, nitrate uptake, nitrogen regulation, urea uptake,
• Publikační typ
• časopisecké články MeSH

Ala and Gly substitutions for Pro 101 (P101) located in transmembrane domain 2 of the dopamine transporter (DAT) abolished transport activity but did not disrupt plasma membrane expression. Due to the high conservation of P101 in all neurotransmitter transporters and the capability of Pro to add flexibility to helices, we hypothesized that P101 contributes to the dynamic feature of substrate translocation. To test this hypothesis, here we analysed transport activity for DAT mutants where this Pro was mutated into different amino acids, including Ser, Val, Leu and Phe. The transmembrane domain 2 helix of P101F, unlike the other mutants, was computationally predicted to have a Van der Waals energy threefold higher than the wild-type helix. P101F mutant expression was consistently disrupted in COS cells. Among all the other mutants that express normally, P101V, with a side-chain size close to that of Pro, restores the transport activity of P101A by sevenfold. Most importantly, P101V, P101L and P101S display negative-dosage effects on dopamine (DA) transport, i.e. the velocity-concentration curve for DA uptake does not show a plateau with increasing [DA] but rather peaks and then goes down. These data support the view that P101 of DAT plays an essential role in DA translocation.

• MeSH
• Cercopithecus aethiops MeSH
• COS buňky MeSH
• dopamin metabolismus   MeSH
• inhibitory vychytávání dopaminu metabolismus   MeSH
• kokain analogy a deriváty   metabolismus   MeSH
• membránové glykoproteiny chemie   genetika   metabolismus   MeSH
• membránové transportní proteiny chemie   genetika   metabolismus   MeSH
• mutageneze cílená * MeSH
• prolin chemie   genetika   MeSH
• proteiny nervové tkáně chemie   genetika   metabolismus   MeSH
• proteiny přenášející dopamin přes plazmatickou membránu MeSH
• substituce aminokyselin genetika   MeSH
• termodynamika MeSH
• tyramin metabolismus   MeSH
• zvířata MeSH
• Check Tag
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• Research Support, N.I.H., Extramural MeSH
• Research Support, U.S. Gov't, P.H.S. MeSH
• srovnávací studie MeSH
• Názvy látek
• (1R-(exo,exo))-3-(4-fluorophenyl)-8-methyl-8- azabicyclo(3.2.1)octane-2-carboxylic acid, methyl ester MeSH Prohlížeč
• dopamin MeSH
• inhibitory vychytávání dopaminu MeSH
• kokain MeSH
• membránové glykoproteiny MeSH
• membránové transportní proteiny MeSH
• prolin MeSH
• proteiny nervové tkáně MeSH
• proteiny přenášející dopamin přes plazmatickou membránu MeSH
• tyramin MeSH

The uptake of stable cesium (133Cs) by Calla palustris was evaluated from four different substrates: water, soil, keramzit (a clay granule) and water with the addition of a potassium compound, after an eight days exposure to a solution of 0.5mM cesium chloride. Stable cesium was used because it is commonly supposed that its uptake by plants is the same of that of radiocesium (137Cs). The plants were differentiated in their parts (roots, healthy leaves, dead leaves and flowers) and analyzed with ICP-MS. The lowest average concentration of absorbed Cs was found in plants exposed in soil (0.7mg/kg, S.D.=96.8), while the highest in plants exposed in water (147mg/kg, S.D.=51.7). During the experiment the water planted plants removed 31.6% of provided Cs while those planted in soil removed only 0.06%. The addition of potassium to water was tested because of the competition effect that arises between these two elements: this effect was confirmed with the result that the average uptake in the presence of potassium was lower (41mg/kg in exposed plants, S.D.=76.1). The uptake was also lower in the solid-based substrates (soil and keramzit), because of the known tendency of Cs to bind with soil particles, thus becoming less available to plants. There was no evidence that the different parts of the plant showed different uptake effectiveness, or that the health of the plant (evaluated with a qualitative method) had any effect on the uptake of Cs.

• Klíčová slova
• (133)Cs, Calla palustris, Phytoremediation, Radiocesium, Stable cesium, Uptake,
• MeSH
• biodegradace MeSH
• Calla (rostlina) metabolismus   MeSH
• cesium metabolismus   farmakologie   MeSH
• chloridy farmakologie   MeSH
• draslík metabolismus   farmakologie   MeSH
• kořeny rostlin metabolismus   MeSH
• látky znečišťující životní prostředí metabolismus   MeSH
• minerály MeSH
• nadzemní části rostlin metabolismus   MeSH
• půda MeSH
• voda MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• cesium chloride MeSH Prohlížeč
• cesium MeSH
• chloridy MeSH
• draslík MeSH
• keramzit MeSH Prohlížeč
• látky znečišťující životní prostředí MeSH
• minerály MeSH
• půda MeSH
• voda MeSH

The pharmacokinetic profile and tissue uptake of daidzein (DAI) was determined in rat serum and tissues (lungs, eyes, brain, heart, spleen, fat, liver, kidney, and testes) after intravenous and intraperitoneal administration of DAI in suspension or complexed with ethylenediamine-modified γ-cyclodextrin (GCD-EDA/DAI). The absolute and relative bioavailability of DAI suspended (20 mg/kg i.v. vs. 50 mg/kg i.p.) and complexed (0.54 mg/kg i.v. vs. 1.35 mg/kg i.p.) was determined. After i.p. administration, absorption of DAI complexed with GCD-EDA was more rapid (tmax = 15 min) than that of DAI in suspension (tmax = 45 min) with a ca. 3.6 times higher maximum concentration (Cmax = 615 vs. 173 ng/mL). The i.v. half-life of DAI was longer in GCD-EDA/DAI complex compared with DAI in suspension (t0.5 = 380 min vs. 230 min). The volume of distribution of DAI given i.v. in GCD-EDA/DAI complex was ca. 6 times larger than DAI in suspension (38.6 L/kg vs. 6.2 L/kg). Our data support the concept that the pharmacokinetics of DAI suspended in high doses are nonlinear. Increasing the intravenous dose 34 times resulted in a 5-fold increase in AUC. In turn, increasing the intraperitoneal dose 37 times resulted in a ca. 2-fold increase in AUC. The results of this study suggested that GCD-EDA complex may improve DAI bioavailability after i.p. administration. The absolute bioavailability of DAI in GCD-EDA inclusion complex was ca. 3 times greater (F = 82.4% vs. 28.2%), and the relative bioavailability was ca. 21 times higher than that of DAI in suspension, indicating the need to study DAI bioavailability after administration by routes other than intraperitoneal, e.g., orally, subcutaneously, or intramuscularly. The concentration of DAI released from GCD-EDA/DAI inclusion complex to all the rat tissues studied was higher than after administration of DAI in suspension. The concentration of DAI in brain and lungs was found to be almost 90 and 45 times higher, respectively, when administered in complex compared to the suspended DAI. Given the nonlinear relationship between DAI bioavailability and the dose released from the GCD-EDA complex, complexation of DAI may thus offer an effective approach to improve DAI delivery for treatment purposes, for example in mucopolysaccharidosis (MPS), allowing the reduction of ingested DAI doses.

• Klíčová slova
• bioavailability, daidzein, nonlinear pharmacokinetics, tissue uptake, γ-cyclodextrin,
• Publikační typ
• časopisecké články MeSH

Candida krusei is a pathogenic yeast species that is phylogenetically outside both of the well-studied yeast groups, whole genome duplication and CUG. Like all other yeast species, it needs to accumulate high amounts of potassium cations, which are needed for proliferation and many other cell functions. A search in the sequenced genomes of nine C. krusei strains revealed the existence of two highly conserved genes encoding putative potassium uptake systems. Both of them belong to the TRK family, whose members have been found in all the sequenced genomes of species from the Saccharomycetales subclade. Analysis and comparison of the two C. krusei Trk sequences revealed all the typical features of yeast Trk proteins but also an unusual extension of the CkTrk2 hydrophilic N-terminus. The expression of both putative CkTRK genes in Saccharomyces cerevisiae lacking its own potassium importers showed that only CkTrk1 is able to complement the absence of S. cerevisiae's own transporters and provide cells with a sufficient amount of potassium. Interestingly, a portion of the CkTrk1 molecules were localized to the vacuolar membrane. The presence of CkTrk2 had no evident phenotype, due to the fact that this protein was not correctly targeted to the S. cerevisiae plasma membrane. Thus, CkTrk2 is the first studied yeast Trk protein to date that was not properly recognized and targeted to the plasma membrane upon heterologous expression in S. cerevisiae.

• Klíčová slova
• Candida, Trk proteins, cation homeostasis, potassium uptake, yeast K+ transporters,
• MeSH
• Candida klasifikace   genetika   růst a vývoj   metabolismus   MeSH
• draslík metabolismus   MeSH
• fungální proteiny genetika   metabolismus   MeSH
• fylogeneze MeSH
• genetická variace MeSH
• genom fungální genetika   MeSH
• iontový transport MeSH
• proteiny přenášející kationty genetika   metabolismus   MeSH
• rekombinantní proteiny genetika   metabolismus   MeSH
• Saccharomyces cerevisiae klasifikace   genetika   růst a vývoj   metabolismus   MeSH
• Saccharomycetales klasifikace   genetika   MeSH
• testy genetické komplementace MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• draslík MeSH
• fungální proteiny MeSH
• proteiny přenášející kationty MeSH
• rekombinantní proteiny MeSH

The ability of thorium uptake as well as responses to heavy metal stress were tested in tobacco cultivar La Burley 21. Thorium was accumulated preferentially in the root system. The presence of citric, tartaric and oxalic acids in hydroponic medium increased thorium accumulation in all plant organs. On the other hand, the addition of diamines and polyamines, the important antioxidants in plants, resulted in decrease of thorium accumulation, especially in the root system. Negative correlation was found between putrescine concentration and thorium accumulation. Nevertheless, the most important factor influencing the accumulation of thorium was the absence of phosphate ions in a hydroponic medium that caused more than 10-fold increase of thorium uptake in all plant parts. Accumulation and distribution of thorium was followed in six cultivars and 14 selected transformants. Cultivar La Barley 21 represented an average between the tested genotypes, having a very good distribution ratio between roots, stems and leaves.

• Klíčová slova
• Citric acid, Phosphate, Plant uptake, Polyamines, Thorium, Tobacco,
• MeSH
• diaminy chemie   farmakologie   MeSH
• fosfáty chemie   nedostatek   MeSH
• genotyp MeSH
• hydroponie MeSH
• ionty chemie   MeSH
• kořeny rostlin účinky léků   metabolismus   MeSH
• listy rostlin účinky léků   metabolismus   MeSH
• polyaminy chemie   farmakologie   MeSH
• putrescin chemie   farmakologie   MeSH
• stonky rostlin účinky léků   metabolismus   MeSH
• tabák metabolismus   MeSH
• thorium chemie   metabolismus   MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• diaminy MeSH
• fosfáty MeSH
• ionty MeSH
• polyaminy MeSH
• putrescin MeSH
• thorium MeSH

Understanding how plant water uptake interacts with acquisition of soil nitrogen (N) and other nutrients is fundamental for predicting plant responses to a changing environment, but it is an area where models disagree. We present a novel isotopic labelling approach which reveals spatial patterns of water and N uptake, and their interaction, by trees. The stable isotopes 15 N and 2 H were applied to a small area of the forest floor in stands with high and low soil N availability. Uptake by surrounding trees was measured. The sensitivity of N acquisition to water uptake was quantified by statistical modelling. Trees in the high-N stand acquired twice as much 15 N as in the low-N stand and around half of their N uptake was dependent on water uptake (2 H enrichment). By contrast, in the low-N stand there was no positive effect of water uptake on N uptake. We conclude that tree N acquisition was only marginally dependent on water flux toward the root surface under low-N conditions whereas under high-N conditions, the water-associated N uptake was substantial. The results suggest a fundamental shift in N acquisition strategy under high-N conditions.

• Klíčová slova
• 15N, Pinus sylvestris (Scots pine), deuterium, diffusion, isotope, mass flow, nitrogen uptake, water uptake,
• MeSH
• borovice lesní * MeSH
• dusík analýza   MeSH
• půda MeSH
• stromy * MeSH
• tajga MeSH
• voda MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• dusík MeSH
• půda MeSH
• voda MeSH

The effect of potassium (K) concentration gradient on stable caesium (Cs) uptake by Calla palustris was studied under hydroponic conditions after eight-day exposure in a greenhouse experiment. The plants were exposed to two different concentrations of Cs (provided as 0.5 and 1 mM CsCl) and five different concentrations of K (provided as K2SO4 in 0.5, 1, 2, 5, and 10 mM). The results indicate negative dependence of Cs uptake on K concentrations for both Cs treatments. The application of K reduced the transfer of stable Cs from water to plant by about 44-72% for 0.5 mM CsCl and 56-74% for 1 mM CsCl. The highest efficiency of Cs removal from water was observed for plants in K+ deficient solutions (plants starving), with an efficiency 8.0% for plants cultivated in 0.5 mM CsCl and 9.4% for plants in 1 mM CsCl. An increasing concentration of K also supported translocation of Cs from roots to leaves. Higher translocation was observed for the treatments with lower level of Cs, where the concentration of Cs in leaves became higher than that in roots. The Cs uptake and translocations were affected not only by the external concentration of K, but also the external concentration of stable Cs. A high concentration of K in the environment protects the food chain from Cs uptake by plants, but lowers the efficiency of phytoremediation techniques.

• Klíčová slova
• Caesium, Calla palustris, Phytoremediation, Potassium, Uptake,
• MeSH
• biodegradace MeSH
• biologický transport účinky léků   fyziologie   MeSH
• Calla (rostlina) metabolismus   MeSH
• cesium analýza   metabolismus   MeSH
• chloridy analýza   metabolismus   MeSH
• draslík metabolismus   farmakologie   MeSH
• kořeny rostlin chemie   metabolismus   MeSH
• listy rostlin chemie   metabolismus   MeSH
• radioaktivní látky znečišťující půdu MeSH
• radioizotopy cesia analýza   metabolismus   MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• cesium chloride MeSH Prohlížeč
• cesium MeSH
• chloridy MeSH
• draslík MeSH
• radioaktivní látky znečišťující půdu MeSH
• radioizotopy cesia MeSH

Epilithon contributes to phosphorus (P) cycling in lakes, but its P uptake traits have been rarely studied. We measured the chemical composition of epilithon and its inorganic P uptake kinetics using isotope 33P in three deep oligo- to mesotrophic post-mining lakes in April, July, and October 2019. Over the sampling period, epilithon biomass doubled, while the P content in biomass dropped to 60% of the April values, and the seasonal changes in P content expressed per epilithon area were only marginal and statistically not significant. High epilithic C:P molar ratios (677 on average) suggested strong P deficiency in all investigated lakes. Regarding the kinetic parameters of phosphorus uptake, maximum uptake velocity (V max , seasonal range 1.9-129 mg P g OM-1 h-1) decreased by an order of magnitude from April to October, while half-saturation constant (K S , seasonal range 3.9-135 mg P L-1) did not show any consistent temporal trend. Values of epilithic specific P uptake affinity (SPUA E , seasonal range 0.08-3.1 L g OM-1 h-1) decreased from spring to autumn and were two to four orders of magnitude lower than the corresponding values for seston (SPUA sest ), which showed an opposite trend. Considering our results, we suggest a possible mechanism underlying a stable coexistence of planktonic and epilithic microorganisms, with plankton prospering mostly in summer and autumn and epilithon in winter and spring season. Additionally, a phenomenon of reversible abiotic P adsorption on epilithon was observed.

• Klíčová slova
• epilithon, hydric recultivation, oligotrophic lakes, periphyton, phosphorus uptake, specific P affinity,
• Publikační typ
• časopisecké články MeSH