TY - THES AB - Metabolic adaptation is a critical feature of migrating cells. It tunes the metabolic programs of migrating cells to allow them to efficiently exert their crucial roles in development, inflammatory responses and tumor metastasis. Cell migration through physically challenging contexts requires energy. However, how the metabolic reprogramming that underlies in vivo cell invasion is controlled is still unanswered. In my PhD project, I identify a novel conserved metabolic shift in Drosophila melanogaster immune cells that by modulating their bioenergetic potential controls developmentally programmed tissue invasion. We show that this regulation requires a novel conserved nuclear protein, named Atossa. Atossa enhances the transcription of a set of proteins, including an RNA helicase Porthos and two metabolic enzymes, each of which increases the tissue invasion of leading Drosophila macrophages and can rescue the atossa mutant phenotype. Porthos selectively regulates the translational efficiency of a subset of mRNAs containing a 5’-UTR cis-regulatory TOP-like sequence. These 5’TOPL mRNA targets encode mitochondrial-related proteins, including subunits of mitochondrial oxidative phosphorylation (OXPHOS) components III and V and other metabolic-related proteins. Porthos powers up mitochondrial OXPHOS to engender a sufficient ATP supply, which is required for tissue invasion of leading macrophages. Atossa’s two vertebrate orthologs rescue the invasion defect. In my PhD project, I elucidate that Atossa displays a conserved developmental metabolic control to modulate metabolic capacities and the cellular energy state, through altered transcription and translation, to aid the tissue infiltration of leading cells into energy demanding barriers. AU - Emtenani, Shamsi ID - 8983 SN - 2663-337X TI - Metabolic regulation of Drosophila macrophage tissue invasion ER - TY - THES AB - Many flows encountered in nature and applications are characterized by a chaotic motion known as turbulence. Turbulent flows generate intense friction with pipe walls and are responsible for considerable amounts of energy losses at world scale. The nature of turbulent friction and techniques aimed at reducing it have been subject of extensive research over the last century, but no definite answer has been found yet. In this thesis we show that in pipes at moderate turbulent Reynolds numbers friction is better described by the power law first introduced by Blasius and not by the Prandtl–von Kármán formula. At higher Reynolds numbers, large scale motions gradually become more important in the flow and can be related to the change in scaling of friction. Next, we present a series of new techniques that can relaminarize turbulence by suppressing a key mechanism that regenerates it at walls, the lift–up effect. In addition, we investigate the process of turbulence decay in several experiments and discuss the drag reduction potential. Finally, we examine the behavior of friction under pulsating conditions inspired by the human heart cycle and we show that under such circumstances turbulent friction can be reduced to produce energy savings. AU - Scarselli, Davide ID - 7258 SN - 2663-337X TI - New approaches to reduce friction in turbulent pipe flow ER - TY - THES AB - Mutations are the raw material of evolution and come in many different flavors. Point mutations change a single letter in the DNA sequence, while copy number mutations like duplications or deletions add or remove many letters of the DNA sequence simultaneously. Each type of mutation exhibits specific properties like its rate of formation and reversal. Gene expression is a fundamental phenotype that can be altered by both, point and copy number mutations. The following thesis is concerned with the dynamics of gene expression evolution and how it is affected by the properties exhibited by point and copy number mutations. Specifically, we are considering i) copy number mutations during adaptation to fluctuating environments and ii) the interaction of copy number and point mutations during adaptation to constant environments.   AU - Tomanek, Isabella ID - 8653 KW - duplication KW - amplification KW - promoter KW - CNV KW - AMGET KW - experimental evolution KW - Escherichia coli SN - 2663-337X TI - The evolution of gene expression by copy number and point mutations ER - TY - THES AB - Self-organization is a hallmark of plant development manifested e.g. by intricate leaf vein patterns, flexible formation of vasculature during organogenesis or its regeneration following wounding. Spontaneously arising channels transporting the phytohormone auxin, created by coordinated polar localizations of PIN-FORMED 1 (PIN1) auxin exporter, provide positional cues for these as well as other plant patterning processes. To find regulators acting downstream of auxin and the TIR1/AFB auxin signaling pathway essential for PIN1 coordinated polarization during auxin canalization, we performed microarray experiments. Besides the known components of general PIN polarity maintenance, such as PID and PIP5K kinases, we identified and characterized a new regulator of auxin canalization, the transcription factor WRKY DNA-BINDING PROTEIN 23 (WRKY23). Next, we designed a subsequent microarray experiment to further uncover other molecular players, downstream of auxin-TIR1/AFB-WRKY23 involved in the regulation of auxin-mediated PIN repolarization. We identified a novel and crucial part of the molecular machinery underlying auxin canalization. The auxin-regulated malectin-type receptor-like kinase CAMEL and the associated leucine-rich repeat receptor-like kinase CANAR target and directly phosphorylate PIN auxin transporters. camel and canar mutants are impaired in PIN1 subcellular trafficking and auxin-mediated repolarization leading to defects in auxin transport, ultimately to leaf venation and vasculature regeneration defects. Our results describe the CAMEL-CANAR receptor complex, which is required for auxin feed-back on its own transport and thus for coordinated tissue polarization during auxin canalization. AU - Hajny, Jakub ID - 8822 SN - 2663-337X TI - Identification and characterization of the molecular machinery of auxin-dependent canalization during vasculature formation and regeneration ER - TY - THES AB - Cytoplasm is a gel-like crowded environment composed of tens of thousands of macromolecules, organelles, cytoskeletal networks and cytosol. The structure of the cytoplasm is thought to be highly organized and heterogeneous due to the crowding of its constituents and their effective compartmentalization. In such an environment, the diffusive dynamics of the molecules is very restricted, an effect that is further amplified by clustering and anchoring of molecules. Despite the jammed nature of the cytoplasm at the microscopic scale, large-scale reorganization of cytoplasm is essential for important cellular functions, such as nuclear positioning and cell division. How such mesoscale reorganization of the cytoplasm is achieved, especially for very large cells such as oocytes or syncytial tissues that can span hundreds of micrometers in size, has only begun to be understood. In this thesis, I focus on the recent advances in elucidating the molecular, cellular and biophysical principles underlying cytoplasmic organization across different scales, structures and species. First, I outline which of these principles have been identified by reductionist approaches, such as in vitro reconstitution assays, where boundary conditions and components can be modulated at ease. I then describe how the theoretical and experimental framework established in these reduced systems have been applied to their more complex in vivo counterparts, in particular oocytes and embryonic syncytial structures, and discuss how such complex biological systems can initiate symmetry breaking and establish patterning. Specifically, I examine an example of large-scale reorganizations taking place in zebrafish embryos, where extensive cytoplasmic streaming leads to the segregation of cytoplasm from yolk granules along the animal-vegetal axis of the embryo. Using biophysical experimentation and theory, I investigate the forces underlying this process, to show that this process does not rely on cortical actin reorganization, as previously thought, but instead on a cell-cycle-dependent bulk actin polymerization wave traveling from the animal to the vegetal pole of the embryo. This wave functions in segregation by both pulling cytoplasm animally and pushing yolk granules vegetally. Cytoplasm pulling is mediated by bulk actin network flows exerting friction forces on the cytoplasm, while yolk granule pushing is achieved by a mechanism closely resembling actin comet formation on yolk granules. This study defines a novel role of bulk actin polymerization waves in embryo polarization via cytoplasmic segregation. Lastly, I describe the cytoplasmic reorganizations taking place during zebrafish oocyte maturation, where the initial segregation of the cytoplasm and yolk granules occurs. Here, I demonstrate a previously uncharacterized wave of microtubule aster formation, traveling the oocyte along the animal-vegetal axis. Further research is required to determine the role of such microtubule structures in cytoplasmic reorganizations therein. Collectively, these studies provide further evidence for the coupling between cell cytoskeleton and cell cycle machinery, which can underlie a core self-organizing mechanism for orchestrating large-scale reorganizations in a cell-cycle-tunable manner, where the modulations of the force-generating machinery and cytoplasmic mechanics can be harbored to fulfill cellular functions. AU - Shamipour, Shayan ID - 8350 SN - 2663-337X TI - Bulk actin dynamics drive phase segregation in zebrafish oocytes ER -