BEGIN:VCALENDAR VERSION:2.0 PRODID:icalendar-ruby CALSCALE:GREGORIAN METHOD:PUBLISH BEGIN:VTIMEZONE TZID:Europe/Vienna BEGIN:DAYLIGHT DTSTART:20290325T030000 TZOFFSETFROM:+0100 TZOFFSETTO:+0200 RRULE:FREQ=YEARLY;BYDAY=-1SU;BYMONTH=3 TZNAME:CEST END:DAYLIGHT BEGIN:STANDARD DTSTART:20281029T020000 TZOFFSETFROM:+0200 TZOFFSETTO:+0100 RRULE:FREQ=YEARLY;BYDAY=-1SU;BYMONTH=10 TZNAME:CET END:STANDARD END:VTIMEZONE BEGIN:VEVENT DTSTAMP:20261106T001000Z UID:1786606200@ist.ac.at DTSTART:20260813T093000 DTEND:20260813T103000 DESCRIPTION:Speaker: Manjunath Javoor\nhosted by Rafal Klajn\nAbstract: Cel l motility depends on the protrusive force generated by the actin cytoskel eton at the leading edge of cells. In lamellipodia\, thin protrusions at t he front of migrating cells\, actin forms higher-order networks with versa tile physical properties. Previous studies have hinted at the presence of different sub-populations of filaments and their spatial organization with in actin filament networks at the leading edge of migrating cells. Due to limitations of existing experimental methods\, it has not been possible to fully describe the complexity of the actin filament populations involved in protrusions at the leading edge.Cryo-electron tomography (cryo-ET) has been used to describe the actin networks in cellular protrusions at single filament resolution in 3D. However\, these descriptions have been limited to 1-2 μm2 area of the protrusions\, providing merely snapshots of much larger assemblies that span serval tens to hundreds of square microns area . Consequently\, they have not provided a holistic overview of the existin g variability within actin networks. We therefore lack a comprehensive und erstanding of how actin network geometries orchestrate cell migration.To a ddress these challenges\, I developed a montage cryo-electron tomography w orkflow to obtain three-dimensional views of lamellipodial regions coverin g areas of up to 100 μm2 at single-filament resolution. Seamless three-di mensional tomogram stitching is achieved by combining neural-network-based denoising strategies with novel optical-flow-based algorithms\, thereby p reserving filament continuity across large reconstructed volumes. Our comp utational analysis pipeline enabled us to vectorize all filaments within t hese volumes\, including filaments reaching lengths of up to 4 μm. The da ta generated here represent a valuable resource for the actin community\, as they provide one of the most detailed and extensive three-dimensional d escriptions of actin filament architecture in the lamellipodium. Specifica lly\, they reveal accurate F-actin concentrations\, filament length distri butions\, connectivity\, and the spatial organization of filament sub-popu lations. These datasets can be used to support and constrain biophysical a nd theoretical models of actin network organization\, dynamics\, and force generation. LOCATION:Sunstone Bldg / Ground floor / Big Seminar Room B / 63 seats (I23. EG.102) and Zoom\, ISTA ORGANIZER: SUMMARY:Manjunath Javoor: Thesis Defense: Large-scale imaging of cellular a ctin networks at single-filament resolution using montage cryo-electron to mography URL:https://talks-calendar.ista.ac.at/events/6576 END:VEVENT BEGIN:VEVENT DTSTAMP:20261106T001000Z UID:1786623300@ist.ac.at DTSTART:20260813T141500 DTEND:20260813T151500 DESCRIPTION:Speaker: Vicente Luis Diaz Melian\nhosted by Kimberly Modic \nA bstract: When a Leidenfrost droplet floats on its own vapor layer\, the in terplay between vapor pressure\, surface tension\, and gravity determines its shape\, and in the stable regime the underside of the droplet exhibits curvature inversion. Using interferometric imaging\, we observe a differe nt behavior for a levitated hydrogel sphere. Curvature inversion appears b riefly after deposition\, but the continuous vaporization process removes this feature\, leading first to an oscillatory regime and eventually to a steady state without curvature inversion. We demonstrate the essential rol e of vaporization in shaping the hydrogel underbelly\, where direct mass l oss has a stronger influence than the balance between vapor pressure and e lastic forces. LOCATION:Central Bldg / O1 / Lecture Hall (I02.O1.014) and Zoom\, ISTA ORGANIZER: SUMMARY:Vicente Luis Diaz Melian: Thesis Defense: The morphology underneath a levitated hydrogel sphere URL:https://talks-calendar.ista.ac.at/events/6561 END:VEVENT BEGIN:VEVENT DTSTAMP:20261106T001000Z UID:1786975200@ist.ac.at DTSTART:20260817T160000 DTEND:20260817T170000 DESCRIPTION:Speaker: Kevin Kögler\nhosted by Krzysztof Pietrzak\nAbstract: Modern datasets often contain as many variables as observations\, or many more\, making classical statistical tools difficult to apply and standard machine-learning models hard to understand. To address this problem\, thi s thesis develops methods for inference and compression in this high-dimen sional regime\, centered on approximate message passing (AMP)\, a family o f iterative inference algorithms which are conjecture to be optimal for ma ny of these problems.First\, we introduce rotationally invariant generaliz ed AMP (RI-GAMP)\, extending AMP beyond independent Gaussian design matric es to a broad class of matrices with complex correlations and arbitrary li miting spectra. We characterize its performance rigorously through state e volution and show that it approaches the performance of Vector AMP while a voiding its computationally expensive singular-value decomposition.We then study nonlinear autoencoders when the input and compressed dimensions gro w proportionally. For Gaussian data\, we derive fundamental limits for one -bit compression by shallow two-layer autoencoders\, characterize their op timal solutions\, and prove that gradient methods reach them. For structur ed data\, however\, a shallow linear decoder may ignore information such a s sparsity and behave exactly as it does for Gaussian inputs. Adding nonli nearities or depth overcomes this limitation: deeper decoders can learn co mputations closely related to AMP and approach optimal reconstruction for a fixed encoder.Finally\, we apply these ideas to predict plasma-protein a bundance from UK Biobank individual-level genetic data\, using approximate ly 8.4 million genetic variants from roughly 40\,000 individuals. A two-st age genetic Vector AMP pipeline first selects a small set of predictive ge nomic regions and then fits more detailed linear or tree-based models. Com bined with a one-hot representation of the genotype data\, this procedure closes the previously reported average gap between linear and deep-learnin g prediction and improves prediction for many proteins in a proteome-wide comparison.  LOCATION:Office Bldg West / Ground floor / Heinzel Seminar Room (I21.EG.101 ) and Zoom\, ISTA ORGANIZER: SUMMARY:Kevin Kögler: Thesis Defense: Compression and Inference in High Di mensions: An Approximate Message Passing Perspective URL:https://talks-calendar.ista.ac.at/events/6577 END:VEVENT BEGIN:VEVENT DTSTAMP:20261106T001000Z UID:1788163200@ist.ac.at DTSTART:20260831T100000 DTEND:20260831T110000 DESCRIPTION:Speaker: Anastasiia Teplova\nhosted by Martin Loose\nAbstract: This thesis comprises two parts addressing distinct questions in plant sig nalling. Part I examines the proposed nucleotide-cyclase activities of pro teins involved in plant hormone signalling. Part II investigates how plant s sense gravity and how this information is translated into a directional growth response.In this thesis defense talk\, I will focus on the second p art and present my research on the molecular mechanisms underlying root gr avitropism. Gravity is perceived in specialized cells called statocytes\, where starch-filled amyloplasts sediment according to the direction of gra vity. This leads to auxin redistribution\, which drives differential growt h and allows the root to bend towards gravity. LZY proteins provide an imp ortant molecular link between statolith sedimentation and the establishmen t of cell polarity. However\, how LZY polarity is connected to the downstr eam regulation of auxin transport remains incompletely understood.My work investigates this connection\, focusing on the dynamic localization and po larization of proteins in root statocytes following root reorientation. In particular\, I examine the relationship between LZY proteins and two pote ntially interconnected systems: AGC kinases involved in regulating PIN aux in transporter activity\, and the RLD–GNOM machinery involved in membran e trafficking and PIN polarity. I show that components of both systems dyn amically redistribute during the gravitropic response and investigate thei r connections with LZY proteins and with each other. Together\, these resu lts contribute to understanding how gravity-induced cell polarity is conne cted to the regulation of auxin transport during root gravitropism. LOCATION:Sunstone Bldg / Ground floor / Big Seminar Room B (I23.EG.102) and Zoom\, ISTA ORGANIZER: SUMMARY:Anastasiia Teplova: Thesis Defense: Chasing the elusive: Investigat ing nucleotide cyclase activity in gibberellin and strigolactone signallin g\; Cellular mechanisms of gravity sensing and response in roots URL:https://talks-calendar.ista.ac.at/events/6593 END:VEVENT BEGIN:VEVENT DTSTAMP:20261106T001000Z UID:1788253200@ist.ac.at DTSTART:20260901T110000 DTEND:20260901T120000 DESCRIPTION:Speaker: Stepan Ovchinnikov\nhosted by Johannes Fink\nAbstract: Bacterial adaptation depends not only on the selective environment but al so on the genetic background that determines which variants can arise and how they affect fitness. This thesis investigates how genetic background a ffects bacterial adaptive capacity by experimentally examining the effect of insertion sequence (IS) elements activity and establishing a strain sys tem for future experiments to reveal the role of natural competence.The ma in experimental study compared Escherichia coli MG1655 with a derivative l acking all 45 chromosomal IS elements\, together with additional strains d esigned to separate the effects of IS removal from restoration of the IS-d isrupted gene wbbL. Replicate populations were adapted to increasing conce ntrations of a five-antibiotic mixture and to each antibiotic individually \, and their adaptive responses and evolutionary routes were compared. Und er mixture selection\, IS-containing and IS-free populations reached simil ar endpoint resistance and acquired similar numbers of mutations\, althoug h their mutation spectra differed significantly. IS-driven mutations were rare\, indicating that IS activity contributed little to adaptation under this condition. Adaptation to individual antibiotics produced larger treat ment-specific resistance gains and more recurrent mutations in the same lo ci across independently evolved populations than adaptation to the antibio tic mixture. The contribution of IS-driven mutations varied among antibiot ics and was highest under tetracycline selection. Under tetracycline treat ment\, IS-containing populations adapted faster and reached higher selecti on concentrations than IS-free populations. Inactivation of wbbL partially restored the adaptive capacity of the IS-free strain but did not fully el iminate the difference\, while IS-containing populations repeatedly access ed IS-mediated mutations unavailable to the IS-free strains.Earlier experi ments examining adaptation to ethanol\, sodium chloride\, and butanol did not provide reliable evidence for differences between the IS backgrounds. Growth observed at high sodium chloride and butanol concentrations during selection was not retained after stress-free recovery\, whereas turbidosta t-based ethanol experiments revealed technical limitations of using the de vice for parallel long-term evolution. These results motivated the more ro bust antibiotic-selection design. Finally\, an experimental framework was developed to test whether natural competence contributes to the adaptive c apacity of Bacillus subtilis. As a first step toward the proposed experime nts\, a genotypically verified ΔcomEC strain and characterized fluorescen t strains were constructed\, but the evolution experiments remain to be in itiated.Together\, these results show that IS elements can expand the repe rtoire of accessible mutations without conferring a universal adaptive adv antage. Whether IS activity improves adaptation depends on the selective e nvironment\, the wider genetic background\, and whether IS-mediated mutati ons provide particularly beneficial adaptive routes. LOCATION:Central Bldg / O1 / Ballroom (I01.O1.006) and Zoom\, ISTA ORGANIZER: SUMMARY:Stepan Ovchinnikov: Thesis Defense: The Role of Genetic Background in Bacterial Adaptation URL:https://talks-calendar.ista.ac.at/events/6601 END:VEVENT BEGIN:VEVENT DTSTAMP:20261106T001000Z UID:1788267600@ist.ac.at DTSTART:20260901T150000 DTEND:20260901T160000 DESCRIPTION:Speaker: Jonas Ingmanns\nhosted by Monika Henzinger\nAbstract: Precise microscopic models of physical processes are often too complex to be useful for understanding or simulating phenomena on a macroscopic scale . The complexity can be drastically reduced if there is a suitable approxi mation which still accurately captures the effective large-scale behavior of the underlying model. This thesis contains contributions to the rigorou s justification of such large-scale approximations  or three different mo dels. Chapter 2 presents joint work with Federico Cornalba\, Julian Fisch er\, and Claudia Raithel. We consider a large system of weakly interacting particles\, driven by independent Brownian motions. The physicists Dean a nd Kawasaki proposed a strongly singular SPDE to describe fluctuations of the particle density. However\, without a suitable regularization\, the De an–Kawasaki equation has been shown to be ill-posed in the sense that it does not admit martingale solutions for any continuous initial data. We s how that a structure-preserving discretization of the Dean–Kawasaki equa tion – acting as a suitable regularization – captures the density fluc tuations of the particle system up to arbitrary order in the inverse numbe r of particles and a discretization error. Chapter 3 presents joint work with Elisa Davoli and Lorenza D’Elia. We consider a magnetic body consis ting of a composite material with a random microstructure. The oscillating magnetic properties are encoded in the micromagnetic energy functional wh ich is restricted to functions taking values on the sphere\, governing the observable states of magnetization. We obtain a qualitative stochastic ho mogenization result in the form of Γ-convergence. The Γ-limit is a micro magnetic energy functional with constant\, deterministic coefficients\, me aning that the magnetic body can be treated as if consisting of a single m aterial when the microstructure is small enough. On a technical level\, we obtain an analogous result replacing the sphere with other sufficiently re gular manifolds.Chapter 4 and Chapter 5 present joint work with Julian Fis cher. We consider interface motions driven by curvature and a uniform forc ing through a stationary field of possibly impenetrable random obstacles s atisfying a finite range of dependence assumption. This process models\, e .g.\, the motion of dislocation lines or magnetic domain boundaries in mat erials with inhibiting impurities. In Chapter 5\, for dimension = 2\, we introduce an easy-to-check criterion for general obstacle fields which imp lies ballistic behavior. More precisely\, this criterion yields an almost guaranteed effective minimum speed on large scales for the interface motio n \, with ‘effective’ meaning that enclosures left behind a main front can be ignored. In Chapter 4\, for any dimension ≥ 2\, assuming such a n almost guaranteed effective minimum speed\, we obtain a quantitative sto chastic homogenization result in any dimension\, proving that the main fro nt can be approximated with a constant-speed motion on large scales. LOCATION:Office Bldg West / Ground floor / Heinzel Seminar Room (I21.EG.101 ) and Zoom\, ISTA ORGANIZER: SUMMARY:Jonas Ingmanns: Thesis Defense: On the large-scale behavior of inte racting particle systems\, composite magnetic materials\, and interface mo tions through random obstacle fields URL:https://talks-calendar.ista.ac.at/events/6560 END:VEVENT BEGIN:VEVENT DTSTAMP:20261106T001000Z UID:1788433200@ist.ac.at DTSTART:20260903T130000 DTEND:20260903T140000 DESCRIPTION:Speaker: Nathalie Gruber\nhosted by Jérémie Palacci\nAbstract : Bacteria inhabit an extraordinary range of environments\, each shaped by its own selective pressures that can fluctuate within seconds to seasons. A persistent selective pressure across these environments is imposed by v iruses that infect bacteria\, called phages. This ongoing coevolution betw een bacteria and phages has led to multiple defense strategies on both sid es. Bacteria have defense strategies at multiple levels: at the cell surfa ce\, physical barriers such as capsules\, exopolysaccharides\, and recepto r modifications limit phage adsorption\, while intracellularly\, molecular defense systems degrade or restrict invading genomes. However\, how these spatially distinct layers are coordinated during infection remains largel y unexplored.To address this\, we investigated the genome-clustered anti-p hage defense island of Escherichia coli K-12\, which encodes four anti-pha ge systems. We found that a single system dominated intracellular defense across diverse phages. Strikingly\, under sustained phage pressure\, a sec ond extracellular layer of defense emerges: phage-induced mucoidy. This is a regulator of capsule synthesis (Rcs)-dependent and quorum-sensing-indep endent response that generates protective extracellular matrix. This mucoi d matrix confers broad resistance\, protecting against 29 of the 31 phages tested. Critically\, the two layers are not independent\; the strength of the defense system-mediated restriction directly sets the phage dose thre shold at which mucoidy is induced. Therefore\, intracellular and extracell ular defenses do not operate in isolation but as a single\, quantitatively coupled immune response.By revealing a direct mechanistic link between in tracellular anti-phage systems and phenotypic switching to mucoidy\, this work reframes bacterial immunity as an integrated\, multi-layered process\ , with broad implications for phage–host coevolution and for the design of phage therapies against mucoid variants\, which are associated with inc reased patient mortality. LOCATION:Central Bldg / O1 / Ballroom (I01.O1.006) and Zoom\, ISTA ORGANIZER: SUMMARY:Nathalie Gruber: Thesis Defense: Genetic Strategies Enabling Bacter ial Adaptation to Selective Pressures URL:https://talks-calendar.ista.ac.at/events/6591 END:VEVENT BEGIN:VEVENT DTSTAMP:20261106T001000Z UID:1788508800@ist.ac.at DTSTART:20260904T100000 DTEND:20260904T110000 DESCRIPTION:Speaker: Andreas Ehrmann\nhosted by Paul Schanda\nAbstract: Bio logy is overwhelmingly good at designing building blocks that are orchestr ated in remarkable processes to enable the functioning of complex organism s. Is it possible to achieve similar complexity in nanotechnology? The fie ld of self-assembly offers a promising route towards bio-inspired function ality. While significant progress has been made in the inverse design of c omplex structures\, little is currently known about embedding these struct ures with dynamics and functional behavior at levels found in biology. Unl ike biology\, we do not have million years of evolution to result in optim al behavior. We aspire to discover fundamental design principles in simple physical systems by taking an optimization approach that builds up on met hods developed by the Machine Learning community to achieve a desired func tion. Many future nanotechnologies will need to do more than hold a desig ned shape: they will need to move\, switch states\, and interact with othe r objects in controlled ways. Is it possible to replicate the precise\, ta rgeted energy delivery of ATP hydrolysis in synthetic systems\, where we c annot rely on biochemical interactions\, to power synthetic nanomachines? In this thesis\, we develop a mechanical model for a controlled energy-del ivery mechanism between bistable nanostructures\, and discover key design features necessary to generate a pathway for efficient energy transduction . Inspired by the universality of ATP hydrolysis\, this achievement could serve as a scheme for powering more and more complex tasks. We show how bi stable nanostructures can be designed so that their conformational changes produce a prescribed behavior. By separating the energetic control of a n anoscale switch from the geometric placement of its binding sites\, we ide ntify which aspects of its energy landscape can be programmed under realis tic constraints. The results provide design principles for turning synthet ic nanostructures into functional\, machine-like objects. By demonstrating how we can translate the scheme for energy delivery to three-state molecu lar machines walking along a track at a very basic level\, we take a first step towards performing a task. We reveal a fundamental speed-efficiency tradeoff and important design considerations. This research contributes to wards designing nanomachines that might eventually be able to contest with the levels of complexity and functionality found in biology. LOCATION:Central Bldg / O1 / Mondi 2a (I01.O1.008)\, ISTA ORGANIZER: SUMMARY:Andreas Ehrmann: Thesis Defense: Biological functionality without b iochemistry: designing nanomachines for target behavior URL:https://talks-calendar.ista.ac.at/events/6578 END:VEVENT BEGIN:VEVENT DTSTAMP:20261106T001000Z UID:1788951600@ist.ac.at DTSTART:20260909T130000 DTEND:20260909T140000 DESCRIPTION:Speaker: Andrea Stöllner\nhosted by Jorryt Matthee\nAbstract: Charge accumulation on aerosol particles plays an important role in a vari ety of natural and industrial processes. An example is cloud electrificati on\, in which collisions between ice crystals and graupel cause large amou nts of charge to be exchanged between airborne particles. Optical tweezers are a highly specialized tool that can hold a single micrometer-sized air borne particle stably in the same position over weeks while measuring its electric charge with elementary-charge resolution. In this work\, we show that the trapping laser can also be used to give charge to the micropartic le. Via a two-photon process the particle acquires more and more positive charge\, enabling us to study its electrical behavior from uncharged up to multiple hundred elementary charges. By studying the dynamics of such hig hly charged particles over days and weeks we find that they spontaneously undergo microdischarges which range from just a few to several hundred ele mentary charges. We show that these discharges are triggered by cosmic-ray muons which pass through the air close to the particle and supply the ion s needed to cause charge loss. Our findings highlight the potential of aer osol optical tweezers to provide new insights into microscale charging and discharging phenomena\, with implications for both fundamental studies an d atmospheric electrification processes. LOCATION:Central Bldg / O1 / Mondi 3 (I01.O1.010)\, ISTA ORGANIZER: SUMMARY:Andrea Stöllner: Thesis Defense: Microscale Electrical Behavior of Highly Charged Individual Aerosol Particles Using Optical Tweezers URL:https://talks-calendar.ista.ac.at/events/6572 END:VEVENT BEGIN:VEVENT DTSTAMP:20261106T001000Z UID:1790074800@ist.ac.at DTSTART:20260922T130000 DTEND:20260922T180000 DESCRIPTION:Abstract: We are excited to announce the 2nd annual Neuroscienc e Faculty Symposium organized by your student neuroscience track represent atives!Every neuroscience PI will hold a brief talk discussing their lab' s current research. The symposium will include catered breaks! Please als o join us for the Pizza Reception following the talks.We look forward to seeing you all there! LOCATION:Raiffeisen Lecture Hall\, ISTA ORGANIZER: SUMMARY:Neuroscience Faculty Symposium URL:https://talks-calendar.ista.ac.at/events/6589 END:VEVENT BEGIN:VEVENT DTSTAMP:20261106T001000Z UID:1792396800@ist.ac.at DTSTART:20261019T100000 DTEND:20261019T110000 DESCRIPTION:Speaker: Adrijana Smoljan\nhosted by Andela Saric\nAbstract: Th e successful colonization of terrestrial environments by plants required t he evolution of developmental and signalling mechanisms that enabled adapt ation to increasingly heterogeneous environments. Among these innovations\ , environmental sensing and directional transport of the plant hormone aux in have played central roles in shaping plant morphology and adaptation to external cues. However\, the evolutionary origins of these regulatory sys tems remain incompletely understood. This thesis investigates two fundamen tal evolutionary questions: when auxin transport mediated by PIN auxin tra nsporters emerged during plant evolution and how MIZ1 proteins acquired th eir role in root hydrotropism.The first part of the thesis examines the ev olution of PIN-FORMED (PIN) auxin transporters using chlorophyte algae and other early-diverging eukaryotic lineages. Physiological analyses demonst rated that chlorophyte algae exhibit concentration-dependent responses to exogenous auxin and possess both passive and energy-dependent auxin transp ort systems\, indicating that fundamental aspects of auxin biology predate the emergence of land plants. Phylogenetic\, structural\, and functional analyses revealed that PIN homologs are broadly distributed across diverse eukaryotic lineages and retain the characteristic PIN protein fold and pr edicted auxin-binding residues. However\, heterologous expression assays i n Xenopus laevis oocytes\, tobacco BY-2 cells\, and Arabidopsis thaliana d emonstrated that these ancestral PIN homologs lack the directional auxin e xport activity characteristic of canonical land plant PIN proteins. Instea d\, they predominantly localize to the endoplasmic reticulum and display l imited or no auxin transport activity\, suggesting that ancestral PIN prot eins primarily functioned in intracellular auxin homeostasis before being recruited for polar auxin transport during land plant evolution.The second part of the thesis investigates the evolutionary diversification of MIZ1 proteins\, key regulators of root hydrotropism in Arabidopsis thaliana. Ph ylogenetic analyses showed that MIZ1 proteins are conserved throughout lan d plants but absent from green algae\, indicating that the protein family originated early during terrestrialization. Although MIZ1 homologs from Ma rchantia polymorpha\, Physcomitrium patens\, Selaginella moellendorffii\, and Amborella trichopoda displayed highly conserved predicted structures a nd endoplasmic reticulum localization\, none were able to complement the h ydrotropic or cytokinin-response defects of the Arabidopsis miz1 mutant. F unctional characterization of Marchantia revealed that MpMIZ1a regulates t hallus development\, cytokinin-dependent growth responses\, expression of cytokinin biosynthetic genes\, and normal sporophyte development\, indicat ing an ancestral role in cytokinin homeostasis and developmental regulatio n rather than hydrotropism. Furthermore\, protein docking predicted an int eraction between MpMIZ1a and its native cytokinin receptor MpCHK\, which w as supported experimentally by bimolecular fluorescence complementation (B iFC). BiFC revealed interactions between the cognate protein pairs MpMIZ1a –MpCHK and AtMIZ1–AtAHK4\, whereas little or no interaction was detect ed for the reciprocal cross-species combinations MpMIZ1a–AtAHK4 and AtMI Z1–MpCHK. This species-specific interaction compatibility provides a pot ential mechanistic explanation for the inability of MpMIZ1a to functionall y complement the Arabidopsis miz1 mutant. Together\, the findings present ed in this thesis demonstrate that both auxin transport and MIZ1 protein f unction evolved through the progressive modification and recruitment of an cestral molecular components. The results support a model in which early P IN proteins primarily regulated intracellular auxin homeostasis before evo lving into specialized plasma membrane auxin exporters\, while MIZ1 protei ns originated as endoplasmic reticulum-associated regulators of cytokinin- dependent development and were subsequently recruited into the hydrotropic signalling pathway of seed plants. By integrating comparative genomics\, structural biology\, molecular genetics\, live-cell imaging\, and physiolo gical analyses across diverse evolutionary lineages\, this work provides n ew insights into the molecular innovations that contributed to the success ful colonization of terrestrial environments and the evolution of developm ental plasticity in land plants. LOCATION:Central Bldg / O1 / Mondi 2a (I01.O1.008)\, ISTA ORGANIZER: SUMMARY:Adrijana Smoljan: Thesis Defense: Evolution of auxin transport and MIZ1-mediated developmental responses during plant adaptation to terrestri al environments URL:https://talks-calendar.ista.ac.at/events/6666 END:VEVENT BEGIN:VEVENT DTSTAMP:20261106T001000Z UID:1792494000@ist.ac.at DTSTART:20261020T130000 DTEND:20261020T140000 DESCRIPTION:Speaker: Yuri Ignatyev\nhosted by Beatriz Vicoso\nAbstract: The spinal cord plays a central role in sensorimotor behavior\, integrating s ensory input and descending commands from the brain to generate movement. Like the brain\, it is composed of diverse populations of excitatory and i nhibitory neurons. Over the course of evolution\, vertebrates have adapted to new environments and evolved distinct body plans\, yet it remains uncl ear how the neuronal architecture of the spinal cord has changed to suppor t these adaptations. Advances in single-cell genomics have made it possibl e to characterize neuronal diversity at single-cell resolution\, but in th e spinal cord such data are largely limited to mammals. To address this ga p and understand how spinal neuronal diversity has evolved\, this thesis c ompares spinal cell types across vertebrates\, including zebrafish\, frog\ , lizard\, mouse and human.First\, we generate a single-cell transcriptomi c atlas of the developing spinal cord of the amphibian Xenopus laevis and compare it with mouse developmental data. This reveals a highly conserved developmental framework across tetrapods\, including conservation of the m ajor cardinal classes\, their spatial distributions and temporal subdivisi ons.Second\, we extend this comparison to the adult spinal cord by generat ing a single-cell and spatial transcriptomic atlas of the frog spinal cord and comparing it with mouse and human data. In contrast to development\, we find marked divergence between amphibians and mammals\, largely restric ted to dorsal excitatory interneurons of the superficial dorsal horn\, inc luding several mammalian-specific populations. Adding zebrafish further su pports the dorsal excitatory compartment as a major site of species-specif ic diversification.Finally\, we characterize the adult spinal cord of the lizard Pogona vitticeps to test whether these populations are specific to mammals or shared across amniotes. This analysis further supports their ma mmalian specificity and links them to late-born dorsal lineages.Together\, these findings suggest that the spinal cord is built on a largely conserv ed developmental framework\, whereas adult neuronal diversity has diverged selectively in the dorsal spinal cord. The superficial dorsal spinal cord thus emerges as a recently evolved hub for sensory integration in mammals . LOCATION:Office Bldg West / Ground floor / Heinzel Seminar Room (I21.EG.101 ) and Zoom\, ISTA ORGANIZER: SUMMARY:Yuri Ignatyev: Thesis Defense: Deciphering spinal interneuron heter ogeneity across vertebrate evolution URL:https://talks-calendar.ista.ac.at/events/6691 END:VEVENT BEGIN:VEVENT DTSTAMP:20261106T001000Z UID:1793619000@ist.ac.at DTSTART:20261102T123000 DTEND:20261102T133000 DESCRIPTION:Speaker: Stavros Papadopoulos\nhosted by Michael Sixt\nAbstract : The evolution of the vertebrate limb-torso-limb body plan drove a divers ification of motor behavior\, with limb and non-limb regions exhibiting in dividual but also crosscoordinated motor repertoires. How neural circuits are organized to generate distinct outputs across body regions\, however\, remains unknown. Amphibians\, the first tetrapods to walk on land\, trans ition to limb locomotion during metamorphosis and offer a unique perspecti ve on the underlying spinal cord transformation. They are separated from m ammals by almost 360 million years of evolution\, and although they share a common limb-torso-limb organization\, they display unique behavioral pat terns along their body axis. Here\, we construct a cross-species\, spatiot emporal atlas of spinal interneurons spanning the rostrocaudal and develop mental axes of frogs and mice. We uncover a common framework of interneuro n regionalization that mirrors each vertebrate’s body plan and motor out put. We find Hoxc9 is a master regulator of both rostrocaudal neuron archi tecture and neurogenesis itself: subtype architecture and progenitor expan sion are transformed thoracic-into-brachial and brachial-into-thoracic by hoxc9 mutation and Hoxc9 overexpression\, respectively. Combining electrop hysiology with computational modelling\, we show that changing regional ci rcuit architecture is sufficient to respecify motor output\, a combined pr oduct of motor and commissural interneurons. Together\, these findings est ablish a causal link between developmental patterning\, circuit architectu re\, and motor function\, identifying interneuron regionalization as a fun damental organizational principle linking bodyplan evolution to motor dive rsity. Our study lays a foundation to further dissect and directly relate individual regional differences in neuron architecture\, such as subtype i dentity\, spatial organization\, and projection pattern\, to motor variati on. And thus\, uncovering how specific behavioral necessities are met by s pinal circuits along the rostrocaudal axis throughout development and acro ss species. LOCATION:Sunstone Bldg / Ground floor / Big Seminar Room B (I23.EG.102) and Zoom\, ISTA ORGANIZER: SUMMARY:Stavros Papadopoulos: Thesis Defense: THE FORM-FUNCTION CONTINUUM O F TETRAPOD SPINAL REGIONALIZATION: Hox-Dependent Neurogenesis\, Architectu re and Output URL:https://talks-calendar.ista.ac.at/events/6709 END:VEVENT BEGIN:VEVENT DTSTAMP:20261106T001000Z UID:1793881800@ist.ac.at DTSTART:20261105T133000 DTEND:20261105T143000 DESCRIPTION:Speaker: Mathias Percipalle\nhosted by Amelia Douglass\nAbstrac t: The Human T-Cell Leukemia virus type 1 (HTLV-1) is an oncogenic deltare trovirus infecting at least 5-10 million people worldwide. It is the causa tive agent of HTLV-1 associated myelopathy/tropical spastic paraparesis (H AM/TSP)\, a spinal cord disease\, and adult T-cell leukemia/lymphoma (ATLL )\, a severe T-cell malignancy. No therapies target HTLV-1 infection\, and many steps of its late-stage viral life cycle remain poorly understood. T his thesis structurally dissects two linked stages of this cycle: the dive rgent immature assembly of HTLV-1\, and its ability to induce an extracell ular-matrix like structure on infected cells\, termed a viral biofilm. Re troviral capsid (CA) proteins display a conserved two-domain architecture consisting of independently folded N-terminal (CA-NTD) and a C-terminal (C A-CTD) subdomains. Yet\, different retrovirus species employ remarkably va riable geometrical solutions to stabilize the CA lattices forming the imma ture virus particle. HTLV-1 relies on the CA-NTD to stabilize its immature lattice\, while the Human Immunodeficiency virus type 1 (HIV-1) relies on a contiguous structural unit formed by the CA-CTD and the spacer peptide 1 (SP1). This raises the question of whether immature assembly phenotypes are modular features encoded independently within individual CA subdomains \, or emergent features requiring strict co-evolution of both subdomains. To test this\, we designed chimeric proteins pairing the CA subdomains of HTLV-1 and HIV-1. Our results show that pairing assembly-driving subdomain s from the two species still allows them to independently form their nativ e immature contacts\, while attempting to impose their preferred curvature on each other. Mutations of either chimeric subdomain do not disrupt asse mbly\, but rather shift the phenotype balance while relieving curvature st rains\, demonstrating that immature assembly properties can be encoded int o a single subdomain. The two-domain architecture of retroviral capsids th us reflects a division of labor built on structural modularity\, where one subdomain is the key driver for assembly competence while the other could serve more regulatory functions.Once assembled and released\, HTLV-1 part icles accumulate at the cell surface within a viral biofilm\, a structure unique among retroviruses that strongly enhances cell-to-cell transmission . However\, the biofilm architecture and virion organization within it\, a nd their influence on virus infectivity\, have not been explored. Using cr yo-electron microscopy methods on purified HTLV-1 biofilm\, we revealed an extracellular environment enriched in virions\, membranous vesicles and m atrix components. Biofilm-embedded virions display large heterogeneity in size and core morphology\, including single and double cores and putative maturation intermediates. Strikingly\, virions are frequently clustered an d tethered to each other and to surrounding membranes by thin linear densi ties whose dimensions match the host restriction factor tetherin\, suggest ing that HTLV-1 may exploit a canonical restriction factor to retain virio ns within the biofilm. We also determined the mature HTLV-1 capsid lattice structure to 9.4 Å resolution from biofilm-embedded particles with canon ical cores. The structure reveals that HTLV-1 still converges onto the mat ure fold conserved across retroviruses\, despite having a divergent immatu re assembly mechanism\, and seemingly undergoes a less dramatic maturation than other retroviruses. Together\, these results expand the structural framework for how HTLV-1 assembles\, matures and organizes itself at the i nfected cell surface. LOCATION:Sunstone Bldg / Ground floor / Big Seminar Room B (I23.EG.102) and Zoom\, ISTA ORGANIZER: SUMMARY:Mathias Percipalle: Thesis Defense: Structurally dissecting the lat e-stage viral lifecycle of the Human T-Cell Leukemia Virus Type 1 URL:https://talks-calendar.ista.ac.at/events/6715 END:VEVENT BEGIN:VEVENT DTSTAMP:20261106T001000Z UID:1794216600@ist.ac.at DTSTART:20261109T103000 DTEND:20261109T113000 DESCRIPTION:Speaker: Chao Shen\nhosted by Maximilian Jösch\nAbstract: It i s a basic property of electromagnetic waves that they propagate. Yet the i mplications of this fact are often glossed over when it comes to nonlinear terahertz (THz) spectroscopy of bulk dielectrics\, with propagation effec ts being given marginal attention. In thick samples\, the THz fields\, opt ical probe\, and nonlinear polarization all propagate with different veloc ities\, experiencing different dispersion\, absorption and birefringence. This gives rise to complicated nonlinear optical interactions prone to mis interpretation in the absence of a comprehensive theoretical framework. Th is thesis combines two-dimensional THz Kerr-effect spectroscopy (2D-TKE)\, two-dimensional THz-field-induced second-harmonic generation (2D-TFISH)\, and propagation-resolved numerical modeling to interpret time-resolved TH z-pump/optical-probe spectroscopies and track nonlinear THz polariton tran sport in bulk dielectrics.In birefringent LaAlO$_3$\, we use 2D-TKE data a nd four-wave-mixing simulations to separate propagation-induced electronic features from the intrinsic Raman-mediated Kerr response. We unambiguousl y identify the $0.86~\\mathrm{THz}$ and $0.36~\\mathrm{THz}$ oscillations in TKE as arising from phase-matched co- and counter-propagating THz-pump/ optical-probe coupling\, whereas the $1.1~\\mathrm{THz}$ oscillation arise s from the $E_g$ Raman phonon in LaAlO$_3$ excited through THz two-photon absorption.In KTaO$_3$\, we identify the origin of the non-oscillatory par t of the TFISH signal by combining single-pulse and 2D-TFISH measurements with simulations based on a Maxwell--Duffing model. We show that propagati ng soft-mode polaritons produce non-local transient polarization inside th e sample. Spatial integration of the TFISH response at different locations acts to single out a polariton mode with a wavevector corresponding to th e phase mismatch between the probe and its second harmonic. A Maxwell--Duf fing model reproduces the temperature and field-strength dependence of bot h the single-pulse and 2D-TFISH signals\, showing that the non-oscillatory component arises purely from nonlinear polariton propagation effects with out invoking transient ferroelectricity. The 2D data also rule out the pro posed mechanisms based on relaxational polar nanoregions or hot phonons.Fi nally\, we develop a spatiotemporal method for tracking soft-mode phonon-p olariton transport in bulk SrTiO$_3$ using 2D-TKE. The nonlinear Kerr sign al is shown to probe the spatial overlap between two independent polariton ic wave packets. Then\, using the less anharmonic $A_{2u}$ polariton as a moving reference\, we track the field-dependent evolution of $E_u$ polarit ons. We observe that anharmonic effects lead to the formation of additiona l polarization accumulation near the sample entrance and an approximately 30\\% increase in the effective velocity of the leading peak of the $E_u$ polariton. A minimal Maxwell--Duffing model captures many qualitative feat ures of the 2D-TKE signal\, including the entrance-layer response\, but pr edicts a substantially weaker velocity renormalization than observed exper imentally. These results establish 2D-TKE as a protocol to trace field-tun able polariton transport in an anharmonic medium\, while revealing behavio r beyond the Maxwell--Duffing description.Together\, these results establi sh propagation as a crucial part of understanding nonlinear THz spectrosco py of bulk dielectrics. Propagation effects can mimic intrinsic material r esponse but\, when identified\, become a sensitive probe of nonlinear latt ice dynamics and transport in quantum materials. LOCATION:Sunstone Bldg / Ground floor / Big Seminar Room A (I23.EG.102) \, ISTA ORGANIZER: SUMMARY:Chao Shen: Propagation-Resolved Nonlinear Terahertz Spectroscopy of Bulk Dielectrics URL:https://talks-calendar.ista.ac.at/events/6683 END:VEVENT BEGIN:VEVENT DTSTAMP:20261106T001000Z UID:1796374800@ist.ac.at DTSTART:20261204T100000 DTEND:20261204T110000 DESCRIPTION:Speaker: Aleksander Bena\nhosted by Calin Guet\nAbstract: Trans ition-metal catalysis has transformed modern organic synthesis\, enabling the efficient and selective formation of chemical bonds. The success of th is field largely depended on the development of tailored ligands that can tune the reactivity of the metal center. Nickel catalysis has emerged as a particularly versatile platform for cross-coupling reactions\, thanks to its ability to access multiple oxidation states. However\, the instability of paramagnetic nickel species can make these reactions difficult to cont rol. Despite the central role of ligands in transition-metal catalysis\, t heir use in tuning the reactivity of such nickel intermediates remains com paratively underexplored. Modular amino-functionalized bipyridine ligands were developed to control the reactivity of Ni(I) intermediates and facil itate challenging elementary steps in cross-coupling catalysis. This appro ach facilitated carbon-carbon and carbon-heteroatom bond formation via Ni( I)/Ni(III) catalytic pathways. Notably\, a new ligand-design facilitated v isible-light induced C(sp²)-heteroatom cross-coupling reactions\, elimina ting the need for an additional photocatalyst and enabling the coupling of a broad range of nitrogen-\, oxygen-\, sulfur- and phosphorus-based nucle ophiles with challenging aryl electrophiles\, using unprecedented low cata lyst loadings. LOCATION:Sunstone Bldg / Ground floor / Big Seminar Room B (I23.EG.102)\, I STA ORGANIZER: SUMMARY:Aleksander Bena: Tuning the Catalytic Reactivity of Ni(I) through L igand Design URL:https://talks-calendar.ista.ac.at/events/6689 END:VEVENT END:VCALENDAR