Cockroaches traverse crevices, crawl rapidly in confined spaces, and inspire a soft, legged robot
Kaushik Jayaram and Robert J. Full
Cockroaches intrude everywhere by exploiting their soft-bodied, shape-changing ability. We discovered that cockroaches traversed horizontal crevices smaller than a quarter of their height in less than a second by compressing their bodies’ compliant exoskeletons in half. Once inside vertically confined spaces, cockroaches still locomoted rapidly at 20 body lengths per second using an unexplored mode of locomotion—body-friction legged crawling. Using materials tests, we found that the compressive forces cockroaches experience when traversing the smallest crevices were 300 times body weight. Cockroaches withstood forces nearly 900 times body weight without injury, explaining their robustness to compression. Cockroach exoskeletons provided inspiration for a soft, legged search-and-rescue robot that may penetrate rubble generated by tornados, earthquakes, or explosions. (See pp. E950–E957.)
Identification of amino acid networks governing catalysis in the closed complex of class I terpene synthases
Patrick Schrepfer, Alexander Buettner, Christian Goerner, Michael Hertel, Jeaphianne van Rijn, Frank Wallrapp, Wolfgang Eisenreich, Volker Sieber, Robert Kourist, and Thomas Brück
Class I terpene synthases are essential in biosynthesis of bioactive terpenoids (e.g., Taxol). Identification of structure–function correlations is hampered by highly dynamic carbocation-driven reactions and the limited availability of catalytically relevant crystal structures. We provide the closed, catalytically active conformations of taxadiene synthase (TXS) and various taxonomically unrelated class I terpene synthases in complex with their catalytically relevant carbocationic intermediates. Our methodology allows direct prediction and validation of universal structural features that govern the highly dynamic catalytic processes of class I terpene synthases. Our data enabled delineation of a discrete reaction pathway for TXS and allowed targeted enzyme engineering to generate alternate macrocyclic core structures, which can act as synthons for bioactive lead structures. (See pp. E958–E967.)
Proteomic comparison defines novel markers to characterize heterogeneous populations of extracellular vesicle subtypes
Joanna Kowal, Guillaume Arras, Marina Colombo, Mabel Jouve, Jakob Paul Morath, Bjarke Primdal-Bengtson, Florent Dingli, Damarys Loew, Mercedes Tkach, and Clotilde Théry
The last decade has seen a rapid expansion of interest in extracellular vesicles (EVs), proposed to mediate cell–cell communication in patho/physiological conditions. Although heterogeneity of EVs has become obvious, as highlighted recently by the International Society for Extracellular Vesicles, the field is lacking specific tools to distinguish EVs of different intracellular origins, and thus probably different functions. Here, thanks to a comprehensive comparison of different types of EVs isolated from a single cell type, we define proteins generically present in EVs, small EV-specific and -excluded ones, and a few specific of endosome-derived exosomes or nonexosomal small EVs. This work will allow proper evaluation of the molecular mechanisms of biogenesis and secretion and the respective functions of subtypes of EVs. (See pp. E968–E977.)
Contrasting effects of intralocus sexual conflict on sexually antagonistic coevolution
Tanya M. Pennell, Freek J. H. de Haas, Edward H. Morrow, and G. Sander van Doorn
Biologists distinguish two forms of conflict between the sexes, recognized as separate drivers of rapid evolution and diversification. Sexual conflict manifests itself as a tug-of-war between selective forces acting on genes jointly expressed by males and females, allowing neither to maximize their fitness. It also appears in mating interactions, where males and females engage in evolutionary arms races to increase their reproductive success to the detriment of their partner. We model the plausible scenario that reproductive traits are involved in both types of conflict and show that their interaction can draw the sexes into perpetual cycles of escalation, alternated by phases of conflict resolution. This result sheds light on the maintenance of sexually antagonistic variation and the complex dynamics of male–female coevolution. (See pp. E978–E986.)
Inbreeding drives maize centromere evolution
Kevin L. Schneider, Zidian Xie, Thomas K. Wolfgruber, and Gernot G. Presting
The diversity of centromere-specific DNA repeats in different species (centromere paradox) and the seemingly parallel rapid evolution of the cenH3 histone protein have previously been interpreted to be related to evolutionary pressures acting on both molecules based on their interaction (centromere drive hypothesis). Here we describe the detailed mechanism and chronology of centromere repeat replacement, and identify inbreeding as a major driver of centromeric DNA replacement that ultimately gives rise to new tandem centromere repeats at genetically indistinguishable loci. These insights explain both the frequently observed disturbance of established centromeres in crop plants following their domestication and the rapid appearance of novel centromere repeat sequences in genetically isolated individuals in nature during speciation. (See pp. E987–E996.)
High expression levels of macrophage migration inhibitory factor sustain the innate immune responses of neonates
Thierry Roger, Anina Schneider, Manuela Weier, Fred C. G. J. Sweep, Didier Le Roy, Jürgen Bernhagen, Thierry Calandra, and Eric Giannoni
During pregnancy, high circulating levels of adenosine and prostaglandins reduce the ability of fetal immune cells to mount powerful proinflammatory responses. In contrast, newborns express 10-fold higher levels of the proinflammatory immune regulator migration inhibitory factor (MIF) compared with adults. MIF sustains cell activation and cytokine production and counterregulates adenosine and prostaglandin E2-mediated immunosuppression in newborn monocytes. Yet excessive MIF expression during an established infection worsens the outcome of newborn mice. Thus, we identify a unique role for MIF in regulating neonatal innate immune responses and propose that MIF has a protective role to reduce susceptibility to infection during the neonatal period but may favor uncontrolled inflammation during sepsis, leading to adverse outcomes. (See pp. E997–E1005.)
Interaction of TAPBPR, a tapasin homolog, with MHC-I molecules promotes peptide editing
Giora I. Morozov, Huaying Zhao, Michael G. Mage, Lisa F. Boyd, Jiansheng Jiang, Michael A. Dolan, Ramesh Venna, Michael A. Norcross, Curtis P. McMurtrey, William Hildebrand, Peter Schuck, Kannan Natarajan, and David H. Margulies
This report explores the biochemical and structural basis of the interactions of TAP binding protein, related (TAPBPR), a tapasin homolog, with MHC-I molecules. TAPBPR associates with MHC-I molecules early in their biosynthesis and folding but is not part of the peptide-loading complex (PLC). Here, by examining the interactions of recombinant TAPBPR with peptide-free and peptide-complexed MHC-I molecules, we show that TAPBPR serves as a peptide editor. Structural comparison of TAPBPR with tapasin indicates the similarities of the two molecules and provides a basis for evaluating the steps of peptide loading. Understanding the molecular underpinnings of peptide loading of MHC-I by TAPBPR and tapasin has wide-ranging influence on our ability to modulate peptide loading for vaccine design and T-cell recognition. (See pp. E1006–E1015.)
Endogenous dendritic cells from the tumor microenvironment support T-ALL growth via IGF1R activation
Todd A. Triplett, Kim T. Cardenas, Jessica N. Lancaster, Zicheng Hu, Hilary J. Selden, Guadalupe J. Jasso, Sadhana Balasubramanyam, Kathy Chan, LiQi Li, Xi Chen, Andrea N. Marcogliese, Utpal P. Davé, Paul E. Love, and Lauren I. R. Ehrlich
T-cell acute lymphoblastic leukemia (T-ALL) is a malignancy of developing T cells. Cancer cell growth is often driven by cell-intrinsic alterations in signaling pathways as well as extrinsic signals from the tumor microenvironment. Here we identify tumor-associated dendritic cells as a key endogenous cell type in the tumor microenvironment that promotes murine T-ALL growth and survival at both primary and metastatic tumor sites. We also find that tumor-associated dendritic cells activate the insulin-like growth factor I receptor in T-ALL cells, which is critical for their survival. Analysis of primary patient T-ALL samples reveals phenotypically analogous tumor microenvironments. Our findings suggest that targeting signals from the tumor microenvironment could expand therapeutic options for T-ALL. (See pp. E1016–E1025.)
ImmunoPET/MR imaging allows specific detection of Aspergillus fumigatus lung infection in vivo
Anna-Maria Rolle, Mike Hasenberg, Christopher R. Thornton, Djamschid Solouk-Saran, Linda Männ, Juliane Weski, Andreas Maurer, Eliane Fischer, Philipp R. Spycher, Roger Schibli, Frederic Boschetti, Sabine Stegemann-Koniszewski, Dunja Bruder, Gregory W. Severin, Stella E. Autenrieth, Sven Krappmann, Genna Davies, Bernd J. Pichler, Matthias Gunzer, and Stefan Wiehr
Invasive pulmonary aspergillosis (IPA) is a frequently fatal lung disease of immunocompromised patients, and is being increasingly reported in individuals with underlying respiratory diseases. Proven diagnosis of IPA currently relies on lung biopsy and detection of diagnostic biomarkers in serum, or in bronchoalveolar lavage fluids. This study supports the use of immunoPET/MR imaging for the diagnosis of IPA, which is so far not used for diagnosis. The antibody-guided imaging technique allows accurate, noninvasive and rapid detection of fungal lung infection and discrimination of IPA from bacterial lung infections and general inflammatory responses. This work demonstrates the applicability of molecular imaging for IPA detection and its potential for aiding clinical diagnosis and management of the disease in the neutropenic host. (See pp. E1026–E1033.)
Cytoplasmic isoforms of Kaposi sarcoma herpesvirus LANA recruit and antagonize the innate immune DNA sensor cGAS
Guigen Zhang, Baca Chan, Naira Samarina, Bizunesh Abere, Magdalena Weidner-Glunde, Anna Buch, Andreas Pich, Melanie M. Brinkmann, and Thomas F. Schulz
In addition to the well-characterized main nuclear latency-associated nuclear antigen (LANA) protein of Kaposi sarcoma herpesvirus (KSHV), cytoplasmic LANA isoforms are known to exist, but their function has thus far been unknown. Here we show that N-terminally truncated cytoplasmic isoforms of LANA play a role in antagonizing the innate response triggered, by means of cGMP-AMP synthase (cGAS) and stimulator of interferon genes (STING), during the reactivation of KSHV from latency. By directly interacting with cGAS, cytoplasmic LANA variants inhibit the cGAS-STING–dependent induction of interferon and thereby promote the reactivation of KSHV from latency. These findings extend the roles of a γ-herpesvirus latent protein into the lytic replication cycle. (See pp. E1034–E1043.)
Defining the rate-limiting processes of bacterial cytokinesis
Carla Coltharp, Jackson Buss, Trevor M. Plumer, and Jie Xiao
Bacterial cytokinesis is orchestrated by a macromolecular complex termed the divisome. Central to the divisome is a ring-like, polymeric structure, called the FtsZ-ring (Z-ring). The Z-ring may generate a constrictive force analogous to that provided by the eukaryotic actomyosin ring to drive membrane invagination during cytokinesis. By combining single-molecule imaging with genetic manipulations, we found that, unexpectedly, the rate of septum closure in Escherichia coli cells during cytokinesis is robust to many substantial Z-ring perturbations but limited by a specific cell wall synthesis enzyme and further modulated by a physical link between the divisome and chromosome. Our results challenge the long-held Z-ring–centric view of bacterial cytokinesis and support a holistic view of constrictive force generation by the multicomponent divisome. (See pp. E1044–E1053.)
A critical role for alternative polyadenylation factor CPSF6 in targeting HIV-1 integration to transcriptionally active chromatin
Gregory A. Sowd, Erik Serrao, Hao Wang, Weifeng Wang, Hind J. Fadel, Eric M. Poeschla, and Alan N. Engelman
HIV-1 requires integration for efficient gene expression, and the local chromatin environment significantly influences the level of HIV-1 transcription. Silent, integrated proviruses constitute the latent HIV reservoir. As HIV-1 commandeers cellular factors to dictate its preferred integration sites, these interactions consequentially influence latency. We examined the impact of polyadenylation specificity factor CPSF6, which binds HIV-1 capsid, and the integrase-binding chromatin reader LEDGF/p75 on viral infection and integration site distribution. Integration sites were determined in cells knocked down or knocked out for one or both host factors. Our data indicate that CPSF6 directs HIV-1 to transcriptionally active chromatin, where LEDGF/p75 predominantly directs the positions of integration within genes. These findings clarify the roles of cellular forces that dictate HIV-1 integration preferences and hence virus pathogenesis. (See pp. E1054–E1063.)
Positive-strand RNA viruses stimulate host phosphatidylcholine synthesis at viral replication sites
Jiantao Zhang, Zhenlu Zhang, Vineela Chukkapalli, Jules A. Nchoutmboube, Jianhui Li, Glenn Randall, George A. Belov, and Xiaofeng Wang
Positive-strand RNA viruses [(+)RNA viruses] include many important human, animal, and plant pathogens. A highly conserved and indispensable feature of (+)RNA virus infection is that these viruses proliferate and reorganize host membranes to assemble viral replication complexes (VRCs). We show that brome mosaic virus (BMV) stimulates phosphatidylcholine (PC) synthesis at the viral replication sites. BMV recruits a host enzyme involved in PC synthesis to support proper VRC formation and genomic replication. We further show that hepatitis C virus and poliovirus also promote accumulation of PC at the viral replication sites, revealing a feature common to a group of (+)RNA viruses. This virus-specific step can be targeted to develop a broad-spectrum antiviral strategy with the least side effects on host growth. (See pp. E1064–E1073.)
Whole-brain calcium imaging with cellular resolution in freely behaving Caenorhabditis elegans
Jeffrey P. Nguyen, Frederick B. Shipley, Ashley N. Linder, George S. Plummer, Mochi Liu, Sagar U. Setru, Joshua W. Shaevitz, and Andrew M. Leifer
Large-scale neural recordings in freely moving animals are important for understanding how patterns of activity across a population of neurons generates animal behavior. Previously, recordings have been limited to either small brain regions or to immobilized or anesthetized animals exhibiting limited behavior. This work records from neurons with cellular resolution throughout the entire brain of the nematode Caenorhabditis elegans during free locomotion. Neurons are found whose activity correlates with behaviors including forward and backward locomotion and turning. A growing body of evidence suggests that animal behavior is sometimes generated by the collective activity of many neurons. It is hoped that methods like this will provide quantitative datasets that yield insights into how brain-wide neural dynamics encode animal action and perception. (See pp. E1074–E1081.)
Pan-neuronal imaging in roaming Caenorhabditis elegans
Vivek Venkatachalam, Ni Ji, Xian Wang, Christopher Clark, James Kameron Mitchell, Mason Klein, Christopher J. Tabone, Jeremy Florman, Hongfei Ji, Joel Greenwood, Andrew D. Chisholm, Jagan Srinivasan, Mark Alkema, Mei Zhen, and Aravinthan D. T. Samuel
A full understanding of sensorimotor transformation during complex behaviors requires quantifying brainwide dynamics of behaving animals. Here, we characterize brainwide dynamics of individual nematodes exposed to a defined thermosensory input. We show that it is possible to uncover representations of sensory input and motor output in individual neurons of behaving animals. Panneuronal imaging in roaming animals will facilitate systems neuroscience in behaving Caenorhabditis elegans. (See pp. E1082–E1088.)
Cortical cholinergic signaling controls the detection of cues
Howard J. Gritton, William M. Howe, Caitlin S. Mallory, Vaughn L. Hetrick, Joshua D. Berke, and Martin Sarter
Virtually the entire cortex is innervated by cholinergic projections from the basal forebrain. Traditionally, this neuronal system has been described as a neuromodulator system that supports global states such as cortical arousal. The presence of fast and regionally specific bursts in cholinergic neurotransmission suggests a more specialized role in cortical processing. Here we used optogenetic methods to investigate the capacity of phasic cholinergic signaling to control behavior. Our findings indicate a causal role of phasic cholinergic signaling in using external cues to guide behavioral choice. These findings indicate the significance of phasic cholinergic activity and also illustrate the potential impact of abnormal, phasic cholinergic neurotransmission on fundamental cognitive functions that involve cue-based behavioral decisions. (See pp. E1089–E1097.)
Variable priming of a docked synaptic vesicle
Jae Hoon Jung, Joseph A. Szule, Robert M. Marshall, and Uel J. McMahan
After synaptic vesicles dock at an active zone on the presynaptic plasma membrane of axon terminals, the vesicles become primed for fusion with the membrane, an essential step in synaptic impulse transmission. We used electron tomography to examine nanometer-scale variations in structural relationships of docked vesicles at the simply arranged active zones of frog neuromuscular junctions. The results, together with prior biochemical and electrophysiological concepts, lead to the hypothesis that priming is regulated by variation in force generated by the shortening and lengthening of macromolecules in the common active zone organelle “active zone material” that links docked vesicles to presynaptic membrane components. Knowledge of mechanisms that regulate synaptic transmission is required for understanding how different synapses accomplish their specialized tasks. (See pp. E1098–E1107.)
Time-coded neurotransmitter release at excitatory and inhibitory synapses
Serafim Rodrigues, Mathieu Desroches, Martin Krupa, Jesus M. Cortes, Terrence J. Sejnowski, and Afia B. Ali
Neurotransmitter exocytosis and short-term synaptic plasticity (STSP) regulate large-scale brain electrical activity. This study is the first, to our knowledge, proposing a multiple-time-scale model that bridges between the microscopic and mesoscopic scales. It is parsimonious, yet with enough descriptive power to express, on the one hand, the interactions between the SNARE and Sec1/Munc18 (SM) protein complexes mediating all forms of neurotransmitter release and STSP and, on the other hand, the electrical activity required for neuronal communication. A key finding is the discovery of a mathematical structure, termed activity-induced transcritical canard, which quantifies and explains delayed and irregular exocytosis. This structure also provides a previously unidentified way to understand delayed and irregular processes sensitive to initial conditions across various biology processes. (See pp. E1108–E1115.)
REDUCED CHLOROPLAST COVERAGE genes from Arabidopsis thaliana help to establish the size of the chloroplast compartment
Robert M. Larkin, Giovanni Stefano, Michael E. Ruckle, Andrea K. Stavoe, Christopher A. Sinkler, Federica Brandizzi, Carolyn M. Malmstrom, and Katherine W. Osteryoung
Mechanisms that determine the cellular volume allocated to organelles are largely unknown. We demonstrate that in the plant Arabidopsis thaliana, a small gene family that encodes proteins of unknown function contributes to a mechanism that establishes the proportion of cellular volume devoted to chloroplasts. We show that this mechanism resides outside of the chloroplast by demonstrating that the protein that makes the greatest contribution to this mechanism resides in the cytoplasm and nucleus and that the trafficking of this protein between the cytoplasm and nucleus may regulate this mechanism. A deeper understanding of this mechanism may lead to the rational manipulation of chloroplast compartment size, which may lead to more efficient photosynthesis and increased yields from important crop plants. (See pp. E1116–E1125.)