Refine
Year of publication
Document Type
- Article (3394) (remove)
Language
- English (3394) (remove)
Is part of the Bibliography
- yes (3394)
Keywords
- Arabidopsis thaliana (40)
- climate change (28)
- Arabidopsis (25)
- ancient DNA (19)
- biodiversity (19)
- Dictyostelium (16)
- functional traits (16)
- Climate change (14)
- animal personality (14)
- competition (14)
Institute
- Institut für Biochemie und Biologie (3394) (remove)
Patterns of sequence divergence in about 1 kb of mitochondrial DNA coding for two genes (16s rRNA and cytochrome oxidase I, COI) were analysed in 13 populations of the fairy shrimp Tanymastix stagnalis from Norway, Germany, France, Italy (northern and central Italy plus insular populations from Sardinia and the Tuscan Archipelago) and Spain, and in one presumed population of Tanymastix stellae from Corsica. The latter species was originally known only from a single locality in Sardinia, which has been destroyed by urbanization; the Corsican population was referred to T stellae by some French authors on the basis of the collection of several cysts from mud. mtDNA data revealed a very low level of genetic divergence between the presumed population of T stellae and the other T stagnalis populations included in the study. Our genetic findings do not support the presence of T stellae in Corsica and are in line with previous SEM studies revealing that all species belonging to the genus Tanymastix produce cysts with identical morphology. The results indicate complex phylogeographic relationships and pronounced genetic differentiation among T stagnalis populations. The islands of Corsica and Sardinia on the one hand and the island of Capraia (Tuscan Archipelago) on the other were probably colonized independently at different times. Genetic relationships among continental populations do not follow a clear geographical trend, indicating that geographical distance is not the main force shaping the pattern of genetic structuring of the species. Stochastic factors such as multiple and independent founder events probably contributed to the striking pattern of genetic differentiation along with subsequent local adaptation. These results agree with previously published molecular work on several groups of aquatic organisms and further support the high potential for dispersal-low gene flow paradox shown by a large array of animals living in lentic habitats
We examined the population genetic structure of the diamondback terrapins (Malaclemys terrapin), within and among estuaries. Based on mark-recapture studies, these estuarine turtles have high site fidelity that is likely to make them vulnerable to local extinctions. We tested if observed site fidelity of adults would be reflected in intraestuarine population genetic structure of six highly polymorphic microsatellite loci (five tetranucleotide and one dinucleotide). No evidence was found for population structuring within the Charleston estuary nor among three different estuaries in South Carolina. We then examined four other terrapin populations from North Carolina to New York, as well as from the Florida Keys and from Texas. With increasing geographical distance, genetic differentiation increased from South Carolina through New York, but overall values were low. The dinucleotide locus contributed significantly more to the genetic differentiation of some population comparisons than any of the other loci. Interestingly, terrapins from South Carolina to New York were much more genetically similar to those from Texas (rho = 0.154) than to those from Florida (rho = 0.357). We attribute this pattern to extensive translocations of terrapins during the early 20th century to replenish diminished populations and to provide turtle farms with stocks. Terrapins collected in Texas were especially sought for shipment to the northeastern US because of their larger size. Our study indicates no population structure within or among adjacent estuaries. Thus, the mark-recapture information from adult and subadult feeding locations is a poor predictor of population genetic structure. Additionally, it appears that past human activities may have drastically altered the genetics of current populations. Finally, our data suggest that translocation of eggs or head starting of terrapins within estuaries or among adjacent estuaries is acceptable from a genetic standpoint
A highly sensitive piezoelectric biosensor has been developed for detection of cholinesterase inhibitors. The inhibitor benzoylecgonine-1,8-diamino-3,4-dioxaoctane (BZE-DADOO) was immobilized on a monolayer of 11- mercaptomonoundecanoic acid (MUA) self-assembled on the gold surface of the sensor. The binding of high-molecular-weight cholinesterase to the immobilized cocaine derivative was monitored with a mass sensitive piezoelectric quartz crystal (quartz crystal nanobalance; QCN). In the presence of an inhibiting substance in the sample, the binding of cholinesterase to the immobilized inhibitor was reduced. The decrease of the rate of mass change was proportional to the concentration of free inhibitor in the sample. This way the affinity sensor followed anti-cholinesterase toxicity and the enzyme activity of ChE was not addressed. A assay for detection of organophosphates (OP) was optimized. Regeneration of the sensor surface was achieved with 1 mol L-1 formic acid, which enabled 40 measurements with one sensor. All assays were carried out in a flow-through arrangement. The total measurement time (binding + regeneration) was 25 min and the detection limit for different OP (paraoxon, diisopropylfluorophosphate, chlorpyriphos, and chlorfenvinphos) was down to 10(-10) mol L-1 (0.02 mu g L-1). This sensor was used for determination of organophosphate (diisopropylfluorophosphate) levels in river water samples
We report here the development of piezoelectric affinity sensors for cocaine and cholinesterase inhibitors based on the formation of affinity complexes between an immobilized cocaine derivative and an anti-cocaine antibody or cholinesterase. For both binding reactions benzoylecgonine-1,8-diamino-3,4-dioxaoctane (BZE-DADOO) was immobilized on the surface of the sensor. For immobilization. pre-conjugated BZE-DADOO with 11-mercaptomonoundecanoic acid (MUA) via 2- (5-norbornen-2,3-dicarboximide)-1,1,3,3-tetramethyluronium-tetrafluoro borate (TNTU) allowed the formation of a chemisorbed monolayer on the piezosensor surface. The detection of cocaine was based oil a competitive assay. The change of frequency measured after 300 s of the binding reaction was used as the signal. The maximum binding of the antibody resulted in a frequency decrease of 35 Hz (with an imprecision 3%, n = 3) while the presence of 100 pmol I-1 cocaine decreased the binding by 11%. The limit of detection was consequently below 100 pmol I-1 for cocaine. The total time of one analysis was 15 min. This BZE-DADOO-modified sensor was adapted for the detection of organophosphates. BZE-DADOO - a competitive inhibitor - served as binding element for cholinesterase in a competitive assay. (C) 2004 Elsevier B.V. All rights reserved
The present study aimed at assessing genetic purity of black wildebeest (Connochoetes gnou) at Abe Bailey Nature Reserve, Gauteng Province, South Africa, using a multitocus microsatellite approach. Five loci were studied in black and blue (C. taurinus) wildebeest, the latter being a closely related species and known to produce hybrids with the morphologically very similar black wildebeest. In fact, the entire national black wildebeest population of South Africa potentially contains a significant proportion of introgressed blue wildebeest genes. In our case, eight out of 39 alleles were unique to black and 22 to blue wildebeest, with nine alleles shared between pure populations of the two species in Line with their taxonomic proximity. A possible Limited past introgression of blue wildebeest genes into the Abe Bailey population, corresponding to documents on population history, was only supported by the presence of a single allele otherwise exclusively found in samples of four pure blue but not in samples of two pure black wildebeest control populations. However, an assignment test and coefficients of population divergence did not support an extended introgression of C. taurinus alleles into the C. gnou population under study. Average heterozygosity at Abe Bailey proved to be intermediate between black and blue wildebeest, the tatter species generally harbouring more genetic variation than the former owing to larger population sizes and the absence of population bottlenecks in historical times. The implications of our data are discussed with reference to the persistence of introgressed genes and the conservation of pure black wildebeest gene pools
Agent-based complex systems are dynamic networks of many interacting agents; examples include ecosystems, financial markets, and cities. The search for general principles underlying the internal organization of such systems often uses bottom-up simulation models such as cellular automata and agent-based models. No general framework for designing, testing, and analyzing bottom-up models has yet been established, but recent advances in ecological modeling have come together in a general strategy we call pattern-oriented modeling. This strategy provides a unifying framework for decoding the internal organization of agent-based complex systems and may lead toward unifying algorithmic theories of the relation between adaptive behavior and system complexity
Diacylglycerol kinase (DGK) regulates the level of the second messenger diacylglycerol and produces phosphatidic acid (PA), another signaling molecule. The Arabidopsis thaliana genome encodes seven putative diacylglycerol kinase isozymes (named AtDGK1 to -7), structurally falling into three major clusters. So far, enzymatic activity has not been reported for any plant Cluster II DGK. Here, we demonstrate that a representative of this cluster, AtDGK7, is biochemically active when expressed as a recombinant protein in Escherichia coli. AtDGK7, encoded by gene locus At4g30340, contains 374 amino acids with an apparent molecular mass of 41.2 kDa. AtDGK7 harbors an N-terminal catalytic domain, but in contrast to various characterized DGKs (including AtDGK2), it lacks a cysteine-rich domain at its N terminus, and, importantly, its C-terminal DGK accessory domain is incomplete. Recombinant AtDGK7 expressed in E. coli exhibits Michaelis-Menten type kinetics with 1,2-dioleoyl-sn-glycerol as substrate. AtDGK7 activity was affected by pH, detergents, and the DGK inhibitor R59022. We demonstrate that both AtDGK2 and AtDGK7 phosphorylate diacylglycerol molecular species that are typically found in plants, indicating that both enzymes convert physiologically relevant substrates. AtDGK7 is expressed throughout the Arabidopsis plant, but expression is strongest in flowers and young seedlings. Expression of AtDGK2 is transiently induced by wounding. R59022 at similar to 80 mu M inhibits root elongation and lateral root formation and reduces plant growth, indicating that DGKs play an important role in plant development
1. The unicellular green alga Chlamydomonas acidophila accumulates in a thin phytoplankton layer in the hypolimnion (deep chlorophyll maximum, DCM) of an extremely acidic lake (Lake 111, pH 2.6, Lusatia, Germany), in which the underwater light spectrum is distorted and red-shifted. 2. Chlamydomonas acidophila exhibited a significantly higher absorption efficiency and a higher cellular chlorophyll b content when incubated in the red shifted underwater light of Lake 111 than in a typical, blue-green dominated, light spectrum. 3. Chlamydomonas acidophila has excellent low light acclimation properties (increased chlorophyll b content, increased oxygen yield and a low light saturation point for photosynthesis) that support survival of the species in the low light climate of the DCM. 4. In situ acclimation to the DCM under low light and temperature decreased maximum photosynthetic rate in autotrophic C. acidophila cultures, whereas the presence of glucose under these conditions enhanced photosynthetic efficiency and capacity. 5. The adaptive abilities of C. acidophila to light and temperature shown in this study, in combination with the absence of potent competitors because of low lake pH, most probably enable the unusual dominance of the green alga in the DCM of Lake 111
In extremely acidic lakes, low primary production rates have been measured. We assumed that proton stress might explain these observations and therefore investigated the photosynthetic behaviour of a Chlamydomonas species, a main primary producer in acidic lakes, over a range of pH values. Identified as C. acidophila using small subunit rDNA analysis, this species is identical to other isolates from acidic environments in Europe and South America, suggesting a worldwide distribution. Laboratory experiments with C. acidophila, revealed a broad pH-tolerance for growth and photosynthesis, the lower pH limit lying at pH 1.5 and the upper limit at pH 7. Growth rates at optimum pH conditions (pH 3 and 5) were equal to those of the mesophilic Chlamydomonas reinhardtii. In contrast, photosynthetic rates were significantly higher, suggesting that higher photosynthetic rates compensated for higher dark respiration rates, as confirmed experimentally. Electron transport capacities of PSI and PSII, P700(+) re-reduction times and measurements of PSII fluorescence revealed the induction of alternative electron transport mechanisms, such as chlororespiration, state transitions and cyclic electron transport, only at suboptimal pH values (pH 1.5; 4 and 6-7). The results indicate, that C. acidophila is well adapted to low pH and that the relatively low primary production rates are not a result of pH stress