TY - JOUR A1 - Zimmermann, P. A1 - Regierer, Babette A1 - Kossmann, Jens A1 - Frossard, Emmanuel A1 - Amrhein, Nikolaus A1 - Bucher, Matthias T1 - Differential expression of three purple acid phosphatases from potato N2 - Three cDNAs encoding purple acid phosphatase (PAP) were cloned from potato (Solanum tuberosum L. cv. Desiree) and expression of the corresponding genes was characterised. StPAP1 encodes a low-molecular weight PAP clustering with mammalian, cyanobacterial, and other plant PAPs. It was highly expressed in stem and root and its expression did not change in response to phosphorus (P) deprivation. StIPAP2 and StPAP3 code for high-molecular weight PAPs typical for plants. Corresponding gene expression was shown to be responsive to the level of P supply, with transcripts of StPAP2 and StPAP3 being most abundant in P-deprived roots or both stem and roots, respectively. Root colonisation by arbuscular mycorrhizal fungi had no effect on the expression of any of the three PAP genes. StIPAP1 mRNA is easily detectable along the root axis, including root hairs, but is barely detectable in root tips. In contrast, both StPAP2 and StPAP3 transcripts are abundant along the root axis, but absent in root hairs, and are most abundant in the root tip. All three PAPs described contain a predicted N-terminal secretion signal and could play a role in extracellular P scavenging, P mobilisation from the rhizosphere, or cell wall regeneration Y1 - 2004 SN - 1435-8603 ER - TY - JOUR A1 - Zbilut, J. P. A1 - Giuliani, A. A1 - Colosimo, A. A1 - Mitchell, J. C. A1 - Colafranceschi, M. A1 - Marwan, Norbert A1 - Webber, C. L. A1 - Uversky, V. N. T1 - Charge and hydrophobicity patterning along the sequence predicts the folding mechanism and aggregation of proteins : a computational approach N2 - The presence of partially folded intermediates along the folding funnel of proteins has been suggested to be a signature of potentially aggregating systems. Many studies have concluded that metastable, highly flexible intermediates are the basic elements of the aggregation process. In a previous paper, we demonstrated how the choice between aggregation and folding behavior was influenced by hydrophobicity distribution patterning along the sequence, as quantified by recurrence quantification analysis (RQA) of the Myiazawa-Jernigan coded primary structures. In the present paper, we tried to unify the "partially folded intermediate" and "hydrophobicity/charge" models of protein aggregation verifying the ability of an empirical relation, developed for rationalizing the effect of different mutations on aggregation propensity of acyl-phosphatase and based on the combination of hydrophobicity RQA and charge descriptors, to discriminate in a statistically significant way two different protein populations: (a) proteins that fold by a process passing by partially folded intermediates and (b) proteins that do not present partially folded intermediates Y1 - 2004 SN - 1535-3893 ER - TY - JOUR A1 - Witt, Isabell A1 - Zanor, Maria Ines A1 - Müller-Röber, Bernd T1 - Transcription factor function search : how do individual factors regulate agronomical important processes in plants? (Subproject A) Y1 - 2004 SN - 3-00-011587-0 ER - TY - JOUR A1 - Wiegand, K. A1 - Jeltsch, Florian A1 - Ward, D. T1 - Minimum recruitment frequency in plants with episodic recruitment N2 - There is concern about the lack of recruitment of Acacia trees in the Negev desert of Israel. We have developed three models to estimate the frequency of recruitment necessary for long-term population survival (i.e. positive average population growth for 1,000 years and <10% probability of extinction). Two models assume purely episodic recruitment based on the general notion that recruitment in and environments is highly episodic. They differ in that the deterministic model investigates average dynamics while the stochastic model does not. Studies indicating that recruitment episodes in and environments have been overemphasized motivated the development of the third model. This semi-stochastic model simulates a mixture of continuous and episodic recruitment. Model analysis was done analytically for the deterministic model and via running model simulations for the stochastic and semi-stochastic models. The deterministic and stochastic models predict that, on average, 2.2 and 3.7 recruitment events per century, respectively, are necessary to sustain the population. According to the semi-stochastic model, 1.6 large recruitment events per century and an annual probability of 50% that a small recruitment event occurs are needed. A consequence of purely episodic recruitment is that all recruitment episodes produce extremely large numbers of recruits (i.e. at odds with field observations), an evaluation that holds even when considering that rare events must be large. Thus, the semi- stochastic model appears to be the most realistic model. Comparing the prediction of the semi-stochastic model to field observations in the Negev desert shows that the absence of observations of extremely large recruitment events is no reason for concern. However, the almost complete absence of small recruitment events is a serious reason for concern. The lack of recruitment may be due to decreased densities of large mammalian herbivores and might be further exacerbated by possible changes in climate, both in terms of average precipitation and the temporal distribution of rain Y1 - 2004 ER - TY - JOUR A1 - Weithoff, Guntram T1 - Vertical niche separation of two consumers (Rotatoria) in an extreme habitat N2 - Herbivore populations are commonly restricted by resource limitation, by predation or a combination of the two. Food supplement experiments are suitable for investigating the extent of food limitation at any given time. The main part of this study was performed in an extremely acidic lake (pH 2.7) where the food web consists of only a few components and potential food sources for herbivores are restricted to two flagellates. Life table experiments proved that Chlamydomonas was a suitable food source whereas Ochromonas was an unsuitable food source. The two flagellates and the two rotifers exhibit a pronounced vertical distribution pattern. In this study, a series of food supplement experiments were performed in order to: (1) quantify and compare potential resource limitation of two primary consumers (Cephalodella hoodi and Elosa worallii, Rotatoria) over time, (2) compare their response at different temperatures, (3) evaluate the effect of having an unsuitable food source alongside a valuable one, (4) estimate the effect of predation on rotifers by Heliozoa, and (5) compare the results with those from other acidic lakes. Additionally, the spatio- temporal population dynamics of both species were observed. The field data confirmed a vertical separation of the two species with E. worallii dominating in the upper water layers, and C. hoodi in the deeper, cooler water layers. The results from the food supplement experiments in which Chlamydomonas served as the supplemented suitable food source showed that the two rotifers were food limited in the epilimnion throughout the season to different extents, with Cephalodella being more severely food limited than Elosa. The experiments at different temperatures provided evidence that Elosa had a higher optimum temperature for growth than Cephalodella. When the unsuitable food algae Ochromonas was added alongside the suitable food source Chlamydomonas, C. hoodi was unaffected but E. worallii was negatively affected. Predation of Heliozoa on rotifers was observed but the total effect on the rotifer dynamics is probably low. The comparison with other lakes showed that resource limitation also occurred in one other lake, although to a lesser extent. Overall, the vertical separation of the two rotifers could be explained by both their differential extent of resource limitation and differential response to temperature. Y1 - 2004 ER - TY - JOUR A1 - Weber, Andreas P. M. A1 - Oesterhelt, Christine A1 - Gross, Wolfgang A1 - Bräutigam, Andrea A1 - Imboden, Lori A1 - Krassovskaya, Inga A1 - Linka, Nicole A1 - Truchina, Julia A1 - Schneidereit, Jörg A1 - Voll, Lars A1 - Zimmermann, Marc A1 - Jamai, Aziz A1 - Riekhof, Wayne A1 - Yu, Bin A1 - Garavito, Michael R. A1 - Benning, Christoph T1 - EST-analysis of the thermo-acidophilic red microalga Galdieria sulphuraria reveals potential for lipid A biosynthesis and unveils the pathway of carbon export from rhodoplasts N2 - When we think of extremophiles, organisms adapted to extreme environments, prokaryotes come to mind first. However, the unicellular red micro-alga Galdieria sulphuraria (Cyanidiales) is a eukaryote that can represent up to 90% of the biomass in extreme habitats such as hot sulfur springs with pH values of 0-4 and temperatures of up to 56 degreesC. This red alga thrives autotrophically as well as heterotrophically on more than 50 different carbon sources, including a number of rare sugars and sugar alcohols. This biochemical versatility suggests a large repertoire of metabolic enzymes, rivaled by few organisms and a potentially rich source of thermo-stable enzymes for biotechnology. The temperatures under which this organism carries out photosynthesis are at the high end of the range for this process, making G. sulphuraria a valuable model for physical studies on the photosynthetic apparatus. In addition, the gene sequences of this living fossil reveal much about the evolution of modern eukaryotes. Finally, the alga tolerates high concentrations of toxic metal ions such as cadmium, mercury, aluminum, and nickel, suggesting potential application in bioremediation. To begin to explore the unique biology of G. sulphuraria, 5270 expressed sequence tags from two different cDNA libraries have been sequenced and annotated. Particular emphasis has been placed on the reconstruction of metabolic pathways present in this organism. For example, we provide evidence for (i) a complete pathway for lipid A biosynthesis; (ii) export of triose-phosphates from rhodoplasts; (iii) and absence of eukaryotic hexokinases. Sequence data and additional information are available at http://genomics.msu.edu/galdieria Y1 - 2004 ER - TY - JOUR A1 - Warncke, Max A1 - Vogt, Birgit A1 - Ulrich, Jacqueline A1 - von Laer, Meike Dorothee A1 - Beyer, Winfried A1 - Klump, Hannes A1 - Micheel, Burkhard A1 - Sheriff, Ahmed T1 - Efficient in vitro transduction of naive murine B cells with lentiviral vectors N2 - The aim of this study was to determine the impact of lentiviral transduction on primary murine B cells. Studying B cell activities in vivo or using them for tolerance induction requires that the cells remain unaltered in their biological behavior except for expression of the transgene. As we show here, murine B cells can efficiently be transduced by lentiviral, VSV-G-pseudotyped vectors without the necessity of prior activation. Culture with LPS gave enhanced transduction efficiencies but led to the upregulation of CD86 and proliferation of the cells. Transduction of naive B cells by lentiviral vectors was dependent on multiplicity of infection and did not lead to a concomitant activation. Furthermore, the transduced cells could be used for studies in the NOD mouse system without altering the onset of diabetes. We conclude that lentiviral gene transfer into naive B cells is a powerful tool for manipulation of B cells for therapeutic applications. Y1 - 2004 UR - http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6WBK-4C707VR- 7&_coverDate=06%2F04%2F2004&_alid=269000954&_rdoc=1&_fmt=&_orig=search&_qd=1&_cdi=6713&_sort=d&view=c&_acct=C000053886&_v e ER - TY - JOUR A1 - Wacker, Alexander A1 - von Elert, Eric T1 - Food quality controls egg quality of the zebra mussel Dreissena polymorpha : The role of fatty acids N2 - We investigated the investment of adult Dreissena polymorpha to the eggs by sampling mussels monthly from 4- and 15-m water depth. The fatty acid composition of eggs differed significantly between depths and over time. To assess whether temperature and food conditions led to the differences observed for mussels sampled from the two depths, mussels were reared in the laboratory under two different 3-month temperature regimes, simulating the temperature of the lake at 4- and 15-m depth. Possible effects of food quality were tested in each simulation using four diets differing in fatty acid composition: Cryptomonas erosa, Nannochloropsis limnetica [rich in polyunsaturated fatty acids (PUFAs) and long- chained PUFAs (.C18)], Scenedesmus obliquus, and the cyanobacterium Aphanothece sp. (deficient in long-chained PUFAs). In newly released eggs, specific (n-3) and (n-6) long-chained PUFAs increased when these fatty acids were available in the natural seston or in the laboratory diets. Mussels fed organisms deficient in long-chained PUFAs were still able to allocate arachidonic acid, eicosapentaenoic acid, and docosahexaenoic acid into eggs, which suggests that minimum levels of particular fatty acids were maintained in eggs by transfer from internal reserves of the female mussels to oocytes. In contrast to the diet, there were no effects of the temperature on the fatty acid composition of eggs. Y1 - 2004 UR - http://aslo.org/lo/toc/vol_49/issue_5/1794.pdf ER - TY - JOUR A1 - Wacker, Alexander A1 - Baur, Bruno T1 - Effects of protein and calcium concentrations of artificial diets on the growth and survival of the land snail Arianta arbustorum N2 - Animals depend on a large set of essential compounds in their food. However, not all units of food are equal from a nutritional point of view. A reduced supply of protein and calcium might be critical for the growth, reproduction and survival of herbivorous gastropods. We experimentally examined the effects of different protein and calcium supplies on the growth and survival of the land snail Arianta arbustorum. Groups of snails were reared on agar-based diets with each of three levels of protein and calcium (nine treatments). Snails fed a high-protein diet grew faster and reached adulthood earlier and at a larger adult size than snails fed intermediate and low-protein diets. Surprisingly, the calcium concentration did not affect shell growth and adult size. Snails reared on intermediate- and low-calcium diets increased their consumption rates, but, despite this compensatory feeding, these snails were unable to take up the amount of calcium required for metabolism and shell growth and had a higher mortality. The calcium deficiency could partly be mitigated by the snails' internal calcium storage and reallocation capacity. A depletion of internal calcium reserves adversely affects the entire nutrient metabolism and was the probable cause for the high mortality rates associated with the intermediate- and low calcium diets observed in the present study Y1 - 2004 SN - 0168-8170 ER - TY - THES A1 - Vigeolas, Helene T1 - Regulation of triacylglycerol biosynthesis in developing seeds of Brassica napus L. and Arabidopsis thaliana (L.) Heyn Y1 - 2004 ER -