Browsing by Subject "Regulation"

Now showing 1 - 7 of 7

Analyse des Flow-abhängigen Symmetriebruchs im Frosch Xenopus : die Funktion des Nodal-Inhibitors Coco
(2015) Getwan, Maike; Blum, Martin
The bilaterally symmetrical vertebrate body plan is characterized by the three body axes, anterior-posterior (AP), dorsal-ventral (DV) and the left-right (LR). The LR-axis is the last one to be specified during embryonic development. Its impact on the morphology of the developing organism is visible after a few days in Xenopus laevis, because of the orientation of the visceral organs, such as the heart, gut and the gall bladder. The first molecular differences between the left and right side can already be detected after one day during early neurulation. It is found at the gastrocoel-roof-plate (GRP), a ciliated epithelium which is essential for symmetry breakage. Cilia rotate to produce a leftward fluid movement, which represses the Cerberus/DAN gene Coco in the lateral cells of the epithelium. As Coco acts as an inhibitor of the coexpressed TGFß-type growth factor Nodal (Xnr1), Xnr1 is flow-dependently released from repression on the left side. Xnr1 is capable to induce a unilateral gene-cascade in the left lateral plate mesoderm (LPM) consisting of Nodal itself, its antagonist Lefty/ antivin and the homeobox gene Pitx2c. A central question in this setting concerns the mechanism by which flow results in the repression of Coco. The analysis of Coco transcription gave a first hint, indicating that Coco mRNA is post-transcriptionally degraded and/ or that its translation is blocked. Gene regulation at the level of mRNA usually occurs through the untranslated regions (UTR), in most cases via the 3UTR. To examine the role of the Coco 3UTR for its regulation, protector-RNAs were used which should protect endogenous Coco mRNA from potential inhibitors. Injections led to the interruption of the flow-dependent Coco repression, verifying regulation of Coco via the 3UTR. As 3UTRs are target sites for microRNAs, loss of function experiments of the processing enzyme Dicer were performed. These experiments verified the involvement of miRNAs in the regulation of Coco. Further analyses identified miR-15a as a central player. The interruption of its synthesis or the specific protection of its binding site within the Coco 3UTR prevented flow-dependent down-regulation of Coco. Epistatic experiments demonstrated that the LR-axis of embryos with inhibited flow could be rescued by addition of the miR-15a precursor on the left side. In summary this thesis work revealed miRNAs as a primary target of leftward flow, upstream of the Nodal inhibitor Coco.
Does regulation trade-off quality against inequality? : The case of German architects and construction engineers
(2018) Strohmaier, Kristina; Rostam-Afschar, Davud
We exploit an exogenous price increase by about 10% for architectural services to answer the question how price regulation affects income inequality and service quality. Using individual-level data from the German microcensus for the years 2006 to 2012, we find a significant reform effect of 8% on personal net income for self-employed architects and construction engineers. This group moved from the second lowest to the highest quintile of the net income distribution. This increase in inequality is associated with a deterioration of service quality. The reform reduced average scores of a peer ranking for architects by 18%.
Entry regulation and competition : evidence from retail and labormarkets of pharmacists
(2021) Unsorg, Maximiliane; Rostam-Afschar, Davud
We examine a deregulation of German pharmacists to assess its effects on retail and labor markets. From 2004 onward, the reform allowed pharmacists to expand their single-store firms and to open or acquire up to three affliated stores. This partial deregulation of multi-store prohibition reduced the cost of firm expansion substantially and provides the basis for our analysis. We develop a theoretical model that suggests that the general limitation of the total store number per firm to four is excessively restrictive. Firms with high managerial effciency will open more stores per furm and have higher labor demand. Our empirical analysis uses very rich information from the administrative panel data on the universe of pharmacies from 2002 to 2009 and their affiliated stores matched with survey data, which provide additional information on the characteristics of expanding firms before and after the reform. We find a sharp immediate increase in entry rates, which continues to be more than five-fold of its pre-reform level after five years for expanding firms. Expanding firms can double revenues but not profits after three years. We show that the increase of the number of employees by 50% after five years and the higher overall employment in the local markets, which increased by 40%, can be attributed to the deregulation.
The functional diversity of the high-affinity nitrate transporter gene family in hexaploid wheat: Insights from distinct expression profiles
(2023) Sigalas, Petros P.; Buchner, Peter; Kröper, Alex; Hawkesford, Malcolm J.
High-affinity nitrate transporters (NRT) are key components for nitrogen (N) acquisition and distribution within plants. However, insights on these transporters in wheat are scarce. This study presents a comprehensive analysis of the NRT2 and NRT3 gene families, where the aim is to shed light on their functionality and to evaluate their responses to N availability. A total of 53 NRT2s and 11 NRT3s were identified in the bread wheat genome, and these were grouped into different clades and homoeologous subgroups. The transcriptional dynamics of the identified NRT2 and NRT3 genes, in response to N starvation and nitrate resupply, were examined by RT-qPCR in the roots and shoots of hydroponically grown wheat plants through a time course experiment. Additionally, the spatial expression patterns of these genes were explored within the plant. The NRT2s of clade 1, TaNRT2.1-2.6, showed a root-specific expression and significant upregulation in response to N starvation, thus emphasizing a role in N acquisition. However, most of the clade 2 NRT2s displayed reduced expression under N-starved conditions. Nitrate resupply after N starvation revealed rapid responsiveness in TaNRT2.1-2.6, while clade 2 genes exhibited gradual induction, primarily in the roots. TaNRT2.18 was highly expressed in above-ground tissues and exhibited distinct nitrate-related response patterns for roots and shoots. The TaNRT3 gene expression closely paralleled the profiles of TaNRT2.1-2.6 in response to nitrate induction. These findings enhance the understanding of NRT2 and NRT3 involvement in nitrogen uptake and utilization, and they could have practical implications for improving nitrogen use efficiency. The study also recommends a standardized nomenclature for wheat NRT2 genes, thereby addressing prior naming inconsistencies.
Kapitalkosten in der Regulierung : Identifizierung und Begrenzung von Freiräumen bei der Bestimmung durch Netzbetreiber und Regulierungsbehörde
(2016) Romer, Andrea; Hachmeister, Dirk
The cost of Capital is an important part of the Network Charge.
Regulation of ammonium transport in Arabidopsis thaliana
(2022) Ganz, Pascal; Ludewig, Uwe
The overarching question of this thesis deals with how plants ensure the selective uptake of ammonium while maintaining ion and pH homeostasis. A key component of this is ammonium transporters (AMTs) with high affinity towards their substrate, which are at the same time part of a multilayered protection system against uncontrolled ammonium influx. Conserved protein sequences inside the transporter were analyzed as well as the regulatory system based on post-translational modification of the transporter.
Understanding the role of the Calcineurin B-like (CBL) proteins and the CBL-Interacting Protein Kinases (CIPK) of wheat (Triticum aestivum) in the regulation of its high affinity ammonium transporters
(2021) Ijato, Toyosi; Ludewig, Uwe
Ammonium is an important nitrogen source whose potential for toxicity (in plants) has been a limitation to its use as a fertilizer. In this work, the response of wheat to ammonium nutrition and the regulatory mechanism governing its high affinity ammonium transporters was investigated. Wheat was able to utilize sole ammonium in the 1 mM range just like sole nitrate. An elevated ammonium concentration of 10 mM caused ammonium induced toxicity effects. Unexpectedly, the wheat seedlings failed to downregulate TaAMT1;1 and TaAMT1;2 in response to elevated ammonium concentration. Nevertheless, TaAMT1;1 and TaAMT1;2 complement ammonium transport in the mep yeast strain (lacking endogenous ammonium transporters). The Voltage dependent ammonium induced currents of the transporters saturated in a concentration dependent manner with Km AMT1;1 = 76 μM and Km AMT1;2 = 196 μM. The affinity of the transporters for ammonium was voltage dependent and indicated that ammonium passes around 35 % of the membrane electric field before rate limiting deprotonation in both transporters. Furthermore, phospho-proteomics study showed the differential phosphorylation of TaAMT1;1 and TaAMT1;2 specific proteotypic phosphopetides. Interestingly, a mutation that mimics phosphorylation at the conserved threonine T453 (T453D) was able to inactivate the ammonium transport function of the transporters. Additionally TaCBL1, and TaCBL2 were able to independently regulate the activity of TaAMT1;1, while TaCBL1, TaCBL2 and TaCBL6 were able to independently impair the ammonium induced current of TaAMT1;2. Subsequently, TaCBL1, TaCBL2 and TaCBL6 interacted with TaCIPK9 to further reduce the ammonium induce current caused by the single TaCBLs proteins on TaAMT1s. TaCIPK23 and TaCIPK32 were only able to regulate TaAMT1;2 by interacting with both TaCBL2 and TaCBL6. Thus, the robust response of wheat to ammonium N was shown to include the phospho-regulation of its high affinity ammonium transporters in a manner that recruits the activity of its TaCBL and TaCIPK proteins.