@article{6093, abstract = {Blebs are cellular protrusions observed in migrating cells and in cells undergoing spreading, cytokinesis, and apoptosis. Here we investigate the flow of cytoplasm during bleb formation and the concurrent changes in cell volume using zebrafish primordial germ cells (PGCs) as an in vivo model. We show that bleb inflation occurs concomitantly with cytoplasmic inflow into it and that during this process the total cell volume does not change. We thus show that bleb formation in primordial germ cells results primarily from redistribution of material within the cell rather than being driven by flow of water from an external source.}, author = {Goudarzi, Mohammad and Boquet-Pujadas, Aleix and Olivo-Marin, Jean Christophe and Raz, Erez}, journal = {PLOS ONE}, number = {2}, publisher = {Public Library of Science}, title = {{Fluid dynamics during bleb formation in migrating cells in vivo}}, doi = {10.1371/journal.pone.0212699}, volume = {14}, year = {2019}, } @article{6095, abstract = {Both classical and recent studies suggest that chromosomal inversion polymorphisms are important in adaptation and speciation. However, biases in discovery and reporting of inversions make it difficult to assess their prevalence and biological importance. Here, we use an approach based on linkage disequilibrium among markers genotyped for samples collected across a transect between contrasting habitats to detect chromosomal rearrangements de novo. We report 17 polymorphic rearrangements in a single locality for the coastal marine snail, Littorina saxatilis. Patterns of diversity in the field and of recombination in controlled crosses provide strong evidence that at least the majority of these rearrangements are inversions. Most show clinal changes in frequency between habitats, suggestive of divergent selection, but only one appears to be fixed for different arrangements in the two habitats. Consistent with widespread evidence for balancing selection on inversion polymorphisms, we argue that a combination of heterosis and divergent selection can explain the observed patterns and should be considered in other systems spanning environmental gradients.}, author = {Faria, Rui and Chaube, Pragya and Morales, Hernán E. and Larsson, Tomas and Lemmon, Alan R. and Lemmon, Emily M. and Rafajlović, Marina and Panova, Marina and Ravinet, Mark and Johannesson, Kerstin and Westram, Anja M and Butlin, Roger K.}, issn = {1365-294X}, journal = {Molecular Ecology}, number = {6}, pages = {1375--1393}, publisher = {Wiley}, title = {{Multiple chromosomal rearrangements in a hybrid zone between Littorina saxatilis ecotypes}}, doi = {10.1111/mec.14972}, volume = {28}, year = {2019}, } @article{6102, abstract = {Light is a union of electric and magnetic fields, and nowhere is the complex relationship between these fields more evident than in the near fields of nanophotonic structures. There, complicated electric and magnetic fields varying over subwavelength scales are generally present, which results in photonic phenomena such as extraordinary optical momentum, superchiral fields, and a complex spatial evolution of optical singularities. An understanding of such phenomena requires nanoscale measurements of the complete optical field vector. Although the sensitivity of near- field scanning optical microscopy to the complete electromagnetic field was recently demonstrated, a separation of different components required a priori knowledge of the sample. Here, we introduce a robust algorithm that can disentangle all six electric and magnetic field components from a single near-field measurement without any numerical modeling of the structure. As examples, we unravel the fields of two prototypical nanophotonic structures: a photonic crystal waveguide and a plasmonic nanowire. These results pave the way for new studies of complex photonic phenomena at the nanoscale and for the design of structures that optimize their optical behavior.}, author = {Le Feber, B. and Sipe, J. E. and Wulf, Matthias and Kuipers, L. and Rotenberg, N.}, issn = {2047-7538}, journal = {Light: Science and Applications}, number = {1}, publisher = {Springer Nature}, title = {{A full vectorial mapping of nanophotonic light fields}}, doi = {10.1038/s41377-019-0124-3}, volume = {8}, year = {2019}, } @article{6104, abstract = {Abiotic stress poses constant challenges for plant survival and is a serious problem for global agricultural productivity. On a molecular level, stress conditions result in elevation of reactive oxygen species (ROS) production causing oxidative stress associated with oxidation of proteins and nucleic acids as well as impairment of membrane functions. Adaptation of root growth to ROS accumulation is facilitated through modification of auxin and cytokinin hormone homeostasis. Here, we report that in Arabidopsis root meristem, ROS-induced changes of auxin levels correspond to decreased abundance of PIN auxin efflux carriers at the plasma membrane (PM). Specifically, increase in H2O2 levels affects PIN2 endocytic recycling. We show that the PIN2 intracellular trafficking during adaptation to oxidative stress requires the function of the ADP-ribosylation factor (ARF)-guanine-nucleotide exchange factor (GEF) BEN1, an actin-associated regulator of the trafficking from the PM to early endosomes and, presumably, indirectly, trafficking to the vacuoles. We propose that H2O2 levels affect the actin dynamics thus modulating ARF-GEF-dependent trafficking of PIN2. This mechanism provides a way how root growth acclimates to stress and adapts to a changing environment.}, author = {Zwiewka, Marta and Bielach, Agnieszka and Tamizhselvan, Prashanth and Madhavan, Sharmila and Ryad, Eman Elrefaay and Tan, Shutang and Hrtyan, Mónika and Dobrev, Petre and Vanková, Radomira and Friml, Jiří and Tognetti, Vanesa B.}, issn = {1471-9053}, journal = {Plant and Cell Physiology}, number = {2}, pages = {255--273}, publisher = {Oxford University Press}, title = {{Root adaptation to H2O2-induced oxidative stress by ARF-GEF BEN1- and cytoskeleton-mediated PIN2 trafficking}}, doi = {10.1093/pcp/pcz001}, volume = {60}, year = {2019}, } @article{6105, abstract = { Hosts can alter their strategy towards pathogens during their lifetime; that is, they can show phenotypic plasticity in immunity or life history. Immune priming is one such example, where a previous encounter with a pathogen confers enhanced protection upon secondary challenge, resulting in reduced pathogen load (i.e., resistance) and improved host survival. However, an initial encounter might also enhance tolerance, particularly to less virulent opportunistic pathogens that establish persistent infections. In this scenario, individuals are better able to reduce the negative fecundity consequences that result from a high pathogen burden. Finally, previous exposure may also lead to life‐history adjustments, such as terminal investment into reproduction. Using different Drosophila melanogaster host genotypes and two bacterial pathogens, Lactococcus lactis and Pseudomonas entomophila, we tested whether previous exposure results in resistance or tolerance and whether it modifies immune gene expression during an acute‐phase infection (one day post‐challenge). We then asked whether previous pathogen exposure affects chronic‐phase pathogen persistence and longer‐term survival (28 days post‐challenge). We predicted that previous exposure would increase host resistance to an early stage bacterial infection while it might come at a cost to host fecundity tolerance. We reasoned that resistance would be due in part to stronger immune gene expression after challenge. We expected that previous exposure would improve long‐term survival, that it would reduce infection persistence, and we expected to find genetic variation in these responses. We found that previous exposure to P. entomophila weakened host resistance to a second infection independent of genotype and had no effect on immune gene expression. Fecundity tolerance showed genotypic variation but was not influenced by previous exposure. However, L. lactis persisted as a chronic infection, whereas survivors cleared the more pathogenic P. entomophila infection. To our knowledge, this is the first study that addresses host tolerance to bacteria in relation to previous exposure, taking a multi‐faceted approach to address the topic. Our results suggest that previous exposure comes with transient costs to resistance during the early stage of infection in this host–pathogen system and that infection persistence may be bacterium‐specific. }, author = {Kutzer, Megan and Kurtz, Joachim and Armitage, Sophie A.O.}, issn = {1365-2656}, journal = {Journal of Animal Ecology}, number = {4}, pages = {566--578}, publisher = {Wiley}, title = {{A multi-faceted approach testing the effects of previous bacterial exposure on resistance and tolerance}}, doi = {10.1111/1365-2656.12953}, volume = {88}, year = {2019}, } @inproceedings{6163, abstract = {We propose a new non-orthogonal basis to express the 3D Euclidean space in terms of a regular grid. Every grid point, each represented by integer 3-coordinates, corresponds to rhombic dodecahedron centroid. Rhombic dodecahedron is a space filling polyhedron which represents the close packing of spheres in 3D space and the Voronoi structures of the face centered cubic (FCC) lattice. In order to illustrate the interest of the new coordinate system, we propose the characterization of 3D digital plane with its topological features, such as the interrelation between the thickness of the digital plane and the separability constraint we aim to obtain. A characterization of a 3D digital sphere with relevant topological features is proposed as well with the help of a 48 symmetry that comes with the new coordinate system.}, author = {Biswas, Ranita and Largeteau-Skapin, Gaëlle and Zrour, Rita and Andres, Eric}, booktitle = {21st IAPR International Conference on Discrete Geometry for Computer Imagery}, isbn = {978-3-6624-6446-5}, issn = {0302-9743}, location = {Marne-la-Vallée, France}, pages = {27--37}, publisher = {Springer Berlin Heidelberg}, title = {{Rhombic dodecahedron grid—coordinate system and 3D digital object definitions}}, doi = {10.1007/978-3-030-14085-4_3}, volume = {11414}, year = {2019}, } @article{6174, abstract = {We propose a scaling theory for the many-body localization (MBL) phase transition in one dimension, building on the idea that it proceeds via a “quantum avalanche.” We argue that the critical properties can be captured at a coarse-grained level by a Kosterlitz-Thouless (KT) renormalization group (RG) flow. On phenomenological grounds, we identify the scaling variables as the density of thermal regions and the length scale that controls the decay of typical matrix elements. Within this KT picture, the MBL phase is a line of fixed points that terminates at the delocalization transition. We discuss two possible scenarios distinguished by the distribution of rare, fractal thermal inclusions within the MBL phase. In the first scenario, these regions have a stretched exponential distribution in the MBL phase. In the second scenario, the near-critical MBL phase hosts rare thermal regions that are power-law-distributed in size. This points to the existence of a second transition within the MBL phase, at which these power laws change to the stretched exponential form expected at strong disorder. We numerically simulate two different phenomenological RGs previously proposed to describe the MBL transition. Both RGs display a universal power-law length distribution of thermal regions at the transition with a critical exponent αc=2, and continuously varying exponents in the MBL phase consistent with the KT picture.}, author = {Dumitrescu, Philipp T. and Goremykina, Anna and Parameswaran, Siddharth A. and Serbyn, Maksym and Vasseur, Romain}, issn = {2469-9969}, journal = {Physical Review B}, number = {9}, publisher = {American Physical Society}, title = {{Kosterlitz-Thouless scaling at many-body localization phase transitions}}, doi = {10.1103/physrevb.99.094205}, volume = {99}, year = {2019}, } @article{6186, abstract = {We prove that the local eigenvalue statistics of real symmetric Wigner-type matrices near the cusp points of the eigenvalue density are universal. Together with the companion paper [arXiv:1809.03971], which proves the same result for the complex Hermitian symmetry class, this completes the last remaining case of the Wigner-Dyson-Mehta universality conjecture after bulk and edge universalities have been established in the last years. We extend the recent Dyson Brownian motion analysis at the edge [arXiv:1712.03881] to the cusp regime using the optimal local law from [arXiv:1809.03971] and the accurate local shape analysis of the density from [arXiv:1506.05095, arXiv:1804.07752]. We also present a PDE-based method to improve the estimate on eigenvalue rigidity via the maximum principle of the heat flow related to the Dyson Brownian motion.}, author = {Cipolloni, Giorgio and Erdös, László and Krüger, Torben H and Schröder, Dominik J}, issn = {2578-5885}, journal = {Pure and Applied Analysis }, number = {4}, pages = {615–707}, publisher = {MSP}, title = {{Cusp universality for random matrices, II: The real symmetric case}}, doi = {10.2140/paa.2019.1.615}, volume = {1}, year = {2019}, } @article{6190, abstract = {Increased levels of the chemokine CCL2 in cancer patients are associated with poor prognosis. Experimental evidence suggests that CCL2 correlates with inflammatory monocyte recruitment and induction of vascular activation, but the functionality remains open. Here, we show that endothelial Ccr2 facilitates pulmonary metastasis using an endothelial-specific Ccr2-deficient mouse model (Ccr2ecKO). Similar levels of circulating monocytes and equal leukocyte recruitment to metastatic lesions of Ccr2ecKO and Ccr2fl/fl littermates were observed. The absence of endothelial Ccr2 strongly reduced pulmonary metastasis, while the primary tumor growth was unaffected. Despite a comparable cytokine milieu in Ccr2ecKO and Ccr2fl/fl littermates the absence of vascular permeability induction was observed only in Ccr2ecKO mice. CCL2 stimulation of pulmonary endothelial cells resulted in increased phosphorylation of MLC2, endothelial cell retraction, and vascular leakiness that was blocked by an addition of a CCR2 inhibitor. These data demonstrate that endothelial CCR2 expression is required for tumor cell extravasation and pulmonary metastasis. Implications: The findings provide mechanistic insight into how CCL2–CCR2 signaling in endothelial cells promotes their activation through myosin light chain phosphorylation, resulting in endothelial retraction and enhanced tumor cell migration and metastasis.}, author = {Roblek, Marko and Protsyuk, Darya and Becker, Paul F. and Stefanescu, Cristina and Gorzelanny, Christian and Glaus Garzon, Jesus F. and Knopfova, Lucia and Heikenwalder, Mathias and Luckow, Bruno and Schneider, Stefan W. and Borsig, Lubor}, issn = {1557-3125}, journal = {Molecular Cancer Research}, number = {3}, pages = {783--793}, publisher = {AACR}, title = {{CCL2 is a vascular permeability factor inducing CCR2-dependent endothelial retraction during lung metastasis}}, doi = {10.1158/1541-7786.MCR-18-0530}, volume = {17}, year = {2019}, } @article{6191, abstract = {The formation of self-organized patterns is key to the morphogenesis of multicellular organisms, although a comprehensive theory of biological pattern formation is still lacking. Here, we propose a minimal model combining tissue mechanics with morphogen turnover and transport to explore routes to patterning. Our active description couples morphogen reaction and diffusion, which impact cell differentiation and tissue mechanics, to a two-phase poroelastic rheology, where one tissue phase consists of a poroelastic cell network and the other one of a permeating extracellular fluid, which provides a feedback by actively transporting morphogens. While this model encompasses previous theories approximating tissues to inert monophasic media, such as Turing’s reaction–diffusion model, it overcomes some of their key limitations permitting pattern formation via any two-species biochemical kinetics due to mechanically induced cross-diffusion flows. Moreover, we describe a qualitatively different advection-driven Keller–Segel instability which allows for the formation of patterns with a single morphogen and whose fundamental mode pattern robustly scales with tissue size. We discuss the potential relevance of these findings for tissue morphogenesis.}, author = {Recho, Pierre and Hallou, Adrien and Hannezo, Edouard B}, issn = {1091-6490}, journal = {Proceedings of the National Academy of Sciences of the United States of America}, number = {12}, pages = {5344--5349}, publisher = {National Academy of Sciences}, title = {{Theory of mechanochemical patterning in biphasic biological tissues}}, doi = {10.1073/pnas.1813255116}, volume = {116}, year = {2019}, } @article{6232, abstract = {The boundary behaviour of solutions of stochastic PDEs with Dirichlet boundary conditions can be surprisingly—and in a sense, arbitrarily—bad: as shown by Krylov[ SIAM J. Math. Anal.34(2003) 1167–1182], for any α>0 one can find a simple 1-dimensional constant coefficient linear equation whose solution at the boundary is not α-Hölder continuous.We obtain a positive counterpart of this: under some mild regularity assumptions on the coefficients, solutions of semilinear SPDEs on C1 domains are proved to be α-Hölder continuous up to the boundary with some α>0.}, author = {Gerencser, Mate}, issn = {0091-1798}, journal = {Annals of Probability}, number = {2}, pages = {804--834}, publisher = {Institute of Mathematical Statistics}, title = {{Boundary regularity of stochastic PDEs}}, doi = {10.1214/18-AOP1272}, volume = {47}, year = {2019}, } @article{6240, abstract = {For a general class of large non-Hermitian random block matrices X we prove that there are no eigenvalues away from a deterministic set with very high probability. This set is obtained from the Dyson equation of the Hermitization of X as the self-consistent approximation of the pseudospectrum. We demonstrate that the analysis of the matrix Dyson equation from (Probab. Theory Related Fields (2018)) offers a unified treatment of many structured matrix ensembles.}, author = {Alt, Johannes and Erdös, László and Krüger, Torben H and Nemish, Yuriy}, issn = {0246-0203}, journal = {Annales de l'institut Henri Poincare}, number = {2}, pages = {661--696}, publisher = {Institut Henri Poincaré}, title = {{Location of the spectrum of Kronecker random matrices}}, doi = {10.1214/18-AIHP894}, volume = {55}, year = {2019}, } @article{6259, abstract = {The plant hormone auxin has crucial roles in almost all aspects of plant growth and development. Concentrations of auxin vary across different tissues, mediating distinct developmental outcomes and contributing to the functional diversity of auxin. However, the mechanisms that underlie these activities are poorly understood. Here we identify an auxin signalling mechanism, which acts in parallel to the canonical auxin pathway based on the transport inhibitor response1 (TIR1) and other auxin receptor F-box (AFB) family proteins (TIR1/AFB receptors)1,2, that translates levels of cellular auxin to mediate differential growth during apical-hook development. This signalling mechanism operates at the concave side of the apical hook, and involves auxin-mediated C-terminal cleavage of transmembrane kinase 1 (TMK1). The cytosolic and nucleus-translocated C terminus of TMK1 specifically interacts with and phosphorylates two non-canonical transcriptional repressors of the auxin or indole-3-acetic acid (Aux/IAA) family (IAA32 and IAA34), thereby regulating ARF transcription factors. In contrast to the degradation of Aux/IAA transcriptional repressors in the canonical pathway, the newly identified mechanism stabilizes the non-canonical IAA32 and IAA34 transcriptional repressors to regulate gene expression and ultimately inhibit growth. The auxin–TMK1 signalling pathway originates at the cell surface, is triggered by high levels of auxin and shares a partially overlapping set of transcription factors with the TIR1/AFB signalling pathway. This allows distinct interpretations of different concentrations of cellular auxin, and thus enables this versatile signalling molecule to mediate complex developmental outcomes.}, author = {Cao, Min and Chen, Rong and Li, Pan and Yu, Yongqiang and Zheng, Rui and Ge, Danfeng and Zheng, Wei and Wang, Xuhui and Gu, Yangtao and Gelová, Zuzana and Friml, Jiří and Zhang, Heng and Liu, Renyi and He, Jun and Xu, Tongda}, issn = {1476-4687}, journal = {Nature}, pages = {240--243}, publisher = {Springer Nature}, title = {{TMK1-mediated auxin signalling regulates differential growth of the apical hook}}, doi = {10.1038/s41586-019-1069-7}, volume = {568}, year = {2019}, } @article{6261, abstract = {Nitrate regulation of root stem cell activity is auxin-dependent.}, author = {Wang, Y and Gong, Z and Friml, Jiří and Zhang, J}, issn = {1532-2548}, journal = {Plant Physiology}, number = {1}, pages = {22--25}, publisher = {ASPB}, title = {{Nitrate modulates the differentiation of root distal stem cells}}, doi = {10.1104/pp.18.01305}, volume = {180}, year = {2019}, } @article{6262, abstract = {Gravitropism is an adaptive response that orients plant growth parallel to the gravity vector. Asymmetric distribution of the phytohormone auxin is a necessary prerequisite to the tropic bending both in roots and shoots. During hypocotyl gravitropic response, the PIN3 auxin transporter polarizes within gravity-sensing cells to redirect intercellular auxin fluxes. First gravity-induced PIN3 polarization to the bottom cell mem- branes leads to the auxin accumulation at the lower side of the organ, initiating bending and, later, auxin feedback-mediated repolarization restores symmetric auxin distribution to terminate bending. Here, we per- formed a forward genetic screen to identify regulators of both PIN3 polarization events during gravitropic response. We searched for mutants with defective PIN3 polarizations based on easy-to-score morphological outputs of decreased or increased gravity-induced hypocotyl bending. We identified the number of hypocotyl reduced bending (hrb) and hypocotyl hyperbending (hhb) mutants, revealing that reduced bending corre- lated typically with defective gravity-induced PIN3 relocation whereas all analyzed hhb mutants showed defects in the second, auxin-mediated PIN3 relocation. Next-generation sequencing-aided mutation map- ping identified several candidate genes, including SCARECROW and ACTIN2, revealing roles of endodermis specification and actin cytoskeleton in the respective gravity- and auxin-induced PIN polarization events. The hypocotyl gravitropism screen thus promises to provide novel insights into mechanisms underlying cell polarity and plant adaptive development.}, author = {Rakusová, Hana and Han, Huibin and Valošek, Petr and Friml, Jiří}, issn = {1365-313x}, journal = {The Plant Journal}, number = {6}, pages = {1048--1059}, publisher = {Wiley}, title = {{Genetic screen for factors mediating PIN polarization in gravistimulated Arabidopsis thaliana hypocotyls}}, doi = {10.1111/tpj.14301}, volume = {98}, year = {2019}, } @article{6297, abstract = {Cell-cell and cell-glycocalyx interactions under flow are important for the behaviour of circulating cells in blood and lymphatic vessels. However, such interactions are not well understood due in part to a lack of tools to study them in defined environments. Here, we develop a versatile in vitro platform for the study of cell-glycocalyx interactions in well-defined physical and chemical settings under flow. Our approach is demonstrated with the interaction between hyaluronan (HA, a key component of the endothelial glycocalyx) and its cell receptor CD44. We generate HA brushes in situ within a microfluidic device, and demonstrate the tuning of their physical (thickness and softness) and chemical (density of CD44 binding sites) properties using characterisation with reflection interference contrast microscopy (RICM) and application of polymer theory. We highlight the interactions of HA brushes with CD44-displaying beads and cells under flow. Observations of CD44+ beads on a HA brush with RICM enabled the 3-dimensional trajectories to be generated, and revealed interactions in the form of stop and go phases with reduced rolling velocity and reduced distance between the bead and the HA brush, compared to uncoated beads. Combined RICM and bright-field microscopy of CD44+ AKR1 T-lymphocytes revealed complementary information about the dynamics of cell rolling and cell morphology, and highlighted the formation of tethers and slings, as they interacted with a HA brush under flow. This platform can readily incorporate more complex models of the glycocalyx, and should permit the study of how mechanical and biochemical factors are orchestrated to enable highly selective blood cell-vessel wall interactions under flow.}, author = {Davies, Heather S. and Baranova, Natalia S. and El Amri, Nouha and Coche-Guérente, Liliane and Verdier, Claude and Bureau, Lionel and Richter, Ralf P. and Débarre, Delphine}, issn = {0945-053X}, journal = {Matrix Biology}, pages = {47--59}, publisher = {Elsevier}, title = {{An integrated assay to probe endothelial glycocalyx-blood cell interactions under flow in mechanically and biochemically well-defined environments}}, doi = {10.1016/j.matbio.2018.12.002}, volume = {78-79}, year = {2019}, } @article{6310, abstract = {An asymptotic formula is established for the number of rational points of bounded anticanonical height which lie on a certain Zariskiopen subset of an arbitrary smooth biquadratic hypersurface in sufficiently many variables. The proof uses the Hardy–Littlewood circle method.}, author = {Browning, Timothy D and Hu, L.Q.}, issn = {1090-2082}, journal = {Advances in Mathematics}, pages = {920--940}, publisher = {Elsevier}, title = {{Counting rational points on biquadratic hypersurfaces}}, doi = {10.1016/j.aim.2019.04.031}, volume = {349}, year = {2019}, } @article{6338, abstract = {Hippocampal activity patterns representing movement trajectories are reactivated in immobility and sleep periods, a process associated with memory recall, consolidation, and decision making. It is thought that only fixed, behaviorally relevant patterns can be reactivated, which are stored across hippocampal synaptic connections. To test whether some generalized rules govern reactivation, we examined trajectory reactivation following non-stereotypical exploration of familiar open-field environments. We found that random trajectories of varying lengths and timescales were reactivated, resembling that of Brownian motion of particles. The animals’ behavioral trajectory did not follow Brownian diffusion demonstrating that the exact behavioral experience is not reactivated. Therefore, hippocampal circuits are able to generate random trajectories of any recently active map by following diffusion dynamics. This ability of hippocampal circuits to generate representations of all behavioral outcome combinations, experienced or not, may underlie a wide variety of hippocampal-dependent cognitive functions such as learning, generalization, and planning.}, author = {Stella, Federico and Baracskay, Peter and O'Neill, Joseph and Csicsvari, Jozsef L}, journal = {Neuron}, pages = {450--461}, publisher = {Elsevier}, title = {{Hippocampal reactivation of random trajectories resembling Brownian diffusion}}, doi = {10.1016/j.neuron.2019.01.052}, volume = {102}, year = {2019}, } @article{6343, abstract = {Cryo-electron tomography (cryo-ET) provides unprecedented insights into the molecular constituents of biological environments. In combination with an image processing method called subtomogram averaging (STA), detailed 3D structures of biological molecules can be obtained in large, irregular macromolecular assemblies or in situ, without the need for purification. The contextual meta-information these methods also provide, such as a protein’s location within its native environment, can then be combined with functional data. This allows the derivation of a detailed view on the physiological or pathological roles of proteins from the molecular to cellular level. Despite their tremendous potential in in situ structural biology, cryo-ET and STA have been restricted by methodological limitations, such as the low obtainable resolution. Exciting progress now allows one to reach unprecedented resolutions in situ, ranging in optimal cases beyond the nanometer barrier. Here, I review current frontiers and future challenges in routinely determining high-resolution structures in in situ environments using cryo-ET and STA.}, author = {Schur, Florian KM}, issn = {0959-440X}, journal = {Current Opinion in Structural Biology}, number = {10}, pages = {1--9}, publisher = {Elsevier}, title = {{Toward high-resolution in situ structural biology with cryo-electron tomography and subtomogram averaging}}, doi = {10.1016/j.sbi.2019.03.018}, volume = {58}, year = {2019}, } @article{6348, abstract = {High-speed optical telecommunication is enabled by wavelength-division multiplexing, whereby hundreds of individually stabilized lasers encode information within a single-mode optical fibre. Higher bandwidths require higher total optical power, but the power sent into the fibre is limited by optical nonlinearities within the fibre, and energy consumption by the light sources starts to become a substantial cost factor1. Optical frequency combs have been suggested to remedy this problem by generating numerous discrete, equidistant laser lines within a monolithic device; however, at present their stability and coherence allow them to operate only within small parameter ranges2,3,4. Here we show that a broadband frequency comb realized through the electro-optic effect within a high-quality whispering-gallery-mode resonator can operate at low microwave and optical powers. Unlike the usual third-order Kerr nonlinear optical frequency combs, our combs rely on the second-order nonlinear effect, which is much more efficient. Our result uses a fixed microwave signal that is mixed with an optical-pump signal to generate a coherent frequency comb with a precisely determined carrier separation. The resonant enhancement enables us to work with microwave powers that are three orders of magnitude lower than those in commercially available devices. We emphasize the practical relevance of our results to high rates of data communication. To circumvent the limitations imposed by nonlinear effects in optical communication fibres, one has to solve two problems: to provide a compact and fully integrated, yet high-quality and coherent, frequency comb generator; and to calculate nonlinear signal propagation in real time5. We report a solution to the first problem.}, author = {Rueda Sanchez, Alfredo R and Sedlmeir, Florian and Kumari, Madhuri and Leuchs, Gerd and Schwefel, Harald G.L.}, issn = {1476-4687}, journal = {Nature}, number = {7752}, pages = {378--381}, publisher = {Springer Nature}, title = {{Resonant electro-optic frequency comb}}, doi = {10.1038/s41586-019-1110-x}, volume = {568}, year = {2019}, }