bluuebunny/crossref_metadata_2025 huggingface dataset:
Small molecule inhibitor of lipoteichoic acid synthesis is an antibiotic for Gram-positive bacteria
Authors: Richter Stefan G. , Elli Derek , Kim Hwan Keun , Hendrickx Antoni P. A. , Sorg Joseph A. , Schneewind Olaf , Missiakas Dominique
Published: February 2013

The current epidemic of infections caused by antibiotic-resistant Gram-positive bacteria requires the discovery of new drug targets and the development of new therapeutics. Lipoteichoic acid (LTA), a cell wall polymer of Gram-positive bacteria, consists of 1,3-polyglycerol-phosphate linked to glycolipid. LTA synthase (LtaS) polymerizes polyglycerol-phosphate from phosphatidylglycerol, a reaction that is essential for the growth of Gram-positive bacteria. We screened small molecule libraries for compounds inhibiting growth of
Staphylococcus aureus
but not of Gram-negative bacteria. Compound 1771 [2-oxo-2-(5-phenyl-1,3,4-oxadiazol-2-ylamino)ethyl 2-naphtho[2,1-
b
]furan-1-ylacetate] blocked phosphatidylglycerol binding to LtaS and inhibited LTA synthesis in
S. aureus
and in
Escherichia coli
expressing
ltaS
. Compound 1771 inhibited the growth of antibiotic-resistant Gram-positive bacteria and prolonged the survival of mice with lethal
S. aureus
challenge, validating LtaS as a target for the development of antibiotics.
Phospholipase Cɛ links G protein-coupled receptor activation to inflammatory astrocytic responses
Authors: Dusaban Stephanie S. , Purcell Nicole H. , Rockenstein Edward , Masliah Eliezer , Cho Min Kyung , Smrcka Alan V. , Brown Joan Heller
Published: February 2013

Neuroinflammation plays a major role in the pathophysiology of diseases of the central nervous system, and the role of astroglial cells in this process is increasingly recognized. Thrombin and the lysophospholipids lysophosphatidic acid and sphingosine 1-phosphate (S1P) are generated during injury and can activate G protein-coupled receptors (GPCRs) on astrocytes. We postulated that GPCRs that couple to Ras homolog gene family, member A (RhoA) induce inflammatory gene expression in astrocytes through the small GTPase responsive phospholipase Cɛ (PLCɛ). Using primary astrocytes from wild-type and PLCɛ knockout mice, we demonstrate that 1-h treatment with thrombin or S1P increases cyclooxygenase 2 (COX-2) mRNA levels ∼10-fold and that this requires PLCɛ. Interleukin-6 and interleukin-1β mRNA levels are also increased in a PLCɛ-dependent manner. Thrombin, lysophosphatidic acid, and S1P increase COX-2 protein expression through a mechanism involving RhoA, catalytically active PLCɛ, sustained activation of protein kinase D (PKD), and nuclear translocation of NF-κB. Endogenous ligands that are released from astrocytes in an in vitro wounding assay also induce COX-2 expression through a PLCɛ- and NF-κB–dependent pathway. Additionally, in vivo stab wound injury activates PKD and induces COX-2 and other inflammatory genes in WT but not in PLCɛ knockout mouse brain. Thus, PLCɛ links GPCRs to sustained PKD activation, providing a means for GPCR ligands that couple to RhoA to induce NF-κB signaling and promote neuroinflammation.
RETRACTED: Voltage sensor ring in a native structure of a membrane-embedded potassium channel
Authors: Shi Liang , Zheng Hongjin , Zheng Hui , Borkowski Brian A. , Shi Dan , Gonen Tamir , Jiang Qiu-Xing
Published: February 2013

Voltage-gated ion channels support electrochemical activity in cells and are largely responsible for information flow throughout the nervous systems. The voltage sensor domains in these channels sense changes in transmembrane potential and control ion flux across membranes. The X-ray structures of a few voltage-gated ion channels in detergents have been determined and have revealed clear structural variations among their respective voltage sensor domains. More recent studies demonstrated that lipids around a voltage-gated channel could directly alter its conformational state in membrane. Because of these disparities, the structural basis for voltage sensing in native membranes remains elusive. Here, through electron-crystallographic analysis of membrane-embedded proteins, we present the detailed view of a voltage-gated potassium channel in its inactivated state. Contrary to all known structures of voltage-gated ion channels in detergents, our data revealed a unique conformation in which the four voltage sensor domains of a voltage-gated potassium channel from
Aeropyrum pernix
(KvAP) form a ring structure that completely surrounds the pore domain of the channel. Such a structure is named the voltage sensor ring. Our biochemical and electrophysiological studies support that the voltage sensor ring represents a physiological conformation. These data together suggest that lipids exert strong effects on the channel structure and that these effects may be changed upon membrane disruption. Our results have wide implications for lipid–protein interactions in general and for the mechanism of voltage sensing in particular.
Deubiquitinase function of arterivirus papain-like protease 2 suppresses the innate immune response in infected host cells
Authors: van Kasteren Puck B. , Bailey-Elkin Ben A. , James Terrence W. , Ninaber Dennis K. , Beugeling Corrine , Khajehpour Mazdak , Snijder Eric J. , Mark Brian L. , Kikkert Marjolein
Published: February 2013

Significance

Many viruses encode proteases that cleave both viral and host substrates. Arteriviruses encode such a dual-specificity protease (PLP2) that removes ubiquitin from cellular proteins involved in host immunity. Based on a 3D structure of PLP2, we engineered the protease to have diminished deubiquitinating activity without affecting its activity toward its viral substrate. Viruses expressing such engineered proteases displayed a significantly weakened ability to evade host immune responses. This result demonstrates a crucial role for PLP2 in arterivirus immune evasion and opens new possibilities for developing improved attenuated virus vaccines against economically important arteriviruses and other viruses encoding similar dual-specificity proteases.
Chicken hemogen homolog is involved in the chicken-specific sex-determining mechanism
Authors: Nakata Tomohiro , Ishiguro Manabu , Aduma Nana , Izumi Hiroe , Kuroiwa Asato
Published: February 2013

Using a comprehensive transcriptome analysis, a Z chromosome-linked chicken homolog of hemogen (
cHEMGN
) was identified and shown to be specifically involved in testis differentiation in early chicken embryos. Hemogen [
Hemgn
in mice,
EDAG
(erythroid differentiation-associated gene protein) in humans] was recently characterized as a hematopoietic tissue-specific gene encoding a transcription factor that regulates the proliferation and differentiation of hematopoietic cells in mammals. In chicken,
cHEMGN
was expressed not only in hematopoietic tissues but also in the early embryonic gonad of male chickens. The male-specific expression was identified in the nucleus of (pre)Sertoli cells after the sex determination period and before the expression of
SOX9
(SRY-box 9). The expression of
cHEMGN
was induced in ZW embryonic gonads that were masculinized by aromatase inhibitor treatment. ZW embryos overexpressing
cHEMGN
, generated by infection with retrovirus carrying
cHEMGN
, showed masculinized gonads. These findings suggest that
cHEMGN
is a transcription factor specifically involved in chicken sex determination.
Posttraining optogenetic manipulations of basolateral amygdala activity modulate consolidation of inhibitory avoidance memory in rats
Authors: Huff Mary L. , Miller Rachel L. , Deisseroth Karl , Moorman David E. , LaLumiere Ryan T.
Published: February 2013

Memory consolidation studies, including those examining the role of the basolateral amygdala (BLA), have traditionally used techniques limited in their temporal and spatial precision. The development of optogenetics provides increased precision in the control of neuronal activity that can be used to address the temporal nature of the modulation of memory consolidation. The present experiments, therefore, investigated whether optogenetically stimulating and inhibiting BLA activity immediately after training on an inhibitory avoidance task enhances and impairs retention, respectively. The BLA of male Sprague–Dawley rats was transduced to express either ChR2(E123A) or archaerhodopsin-3 from the
Halorubrum sodomense
strain TP009 (ArchT). Immediately after inhibitory avoidance training, rats received optical stimulation or inhibition of the BLA, and 2 d later, rats’ retention was tested. Stimulation of ChR2(E123A)-expressing neurons in the BLA using trains of 40-Hz light pulses enhanced retention, consistent with recording studies suggesting the importance of BLA activity at this frequency. Light pulses alone given to control rats had no effect on retention. Inhibition of ArchT-expressing neurons in the BLA for 15 min, but not 1 min, significantly impaired retention. Again, illumination alone given to control rats had no effect on retention, and BLA inhibition 3 h after training had no effect. These findings provide critical evidence of the importance of specific frequency patterns of activity in the BLA during consolidation and indicate that optogenetic manipulations can be used to alter activity after a learning event to investigate the processes underlying memory consolidation.
Ultralocalized thermal reactions in subnanoliter droplets-in-air
Authors: Salm Eric , Guevara Carlos Duarte , Dak Piyush , Dorvel Brian Ross , Reddy Bobby , Alam Muhammad Ashraf , Bashir Rashid
Published: February 2013

Miniaturized laboratory-on-chip systems promise rapid, sensitive, and multiplexed detection of biological samples for medical diagnostics, drug discovery, and high-throughput screening. Within miniaturized laboratory-on-chips, static and dynamic droplets of fluids in different immiscible media have been used as individual vessels to perform biochemical reactions and confine the products. Approaches to perform localized heating of these individual subnanoliter droplets can allow for new applications that require parallel, time-, and space-multiplex reactions on a single integrated circuit. Our method positions droplets on an array of individual silicon microwave heaters on chip to precisely control the temperature of droplets-in-air, allowing us to perform biochemical reactions, including DNA melting and detection of single base mismatches. We also demonstrate that ssDNA probe molecules can be placed on heaters in solution, dried, and then rehydrated by ssDNA target molecules in droplets for hybridization and detection. This platform enables many applications in droplets including hybridization of low copy number DNA molecules, lysing of single cells, interrogation of ligand–receptor interactions, and rapid temperature cycling for amplification of DNA molecules.
Evidence for participation of the methionine sulfoxide reductase repair system in plant seed longevity
Authors: Châtelain Emilie , Satour Pascale , Laugier Edith , Ly Vu Benoit , Payet Nicole , Rey Pascal , Montrichard Françoise
Published: February 2013

Seeds are in a natural oxidative context leading to protein oxidation. Although inevitable for proper progression from maturation to germination, protein oxidation at high levels is detrimental and associated with seed aging. Oxidation of methionine to methionine sulfoxide is a common form of damage observed during aging in all organisms. This damage is reversible through the action of methionine sulfoxide reductases (MSRs), which play key roles in lifespan control in yeast and animal cells. To investigate the relationship between MSR capacity and longevity in plant seeds, we first used two
Medicago truncatula
genotypes with contrasting seed quality. After characterizing the MSR family in this species, we analyzed gene expression and enzymatic activity in immature and mature seeds exhibiting distinct quality levels. We found a very strong correlation between the initial MSR capacities in different lots of mature seeds of the two genotypes and the time to a drop in viability to 50% after controlled deterioration. We then analyzed seed longevity in
Arabidopsis thaliana
lines, in which MSR gene expression has been genetically altered, and observed a positive correlation between MSR capacity and longevity in these seeds as well. Based on our data, we propose that the MSR repair system plays a decisive role in the establishment and preservation of longevity in plant seeds.
Persistent whole-chromosome aneuploidy is generally associated with nascent allohexaploid wheat
Authors: Zhang Huakun , Bian Yao , Gou Xiaowan , Zhu Bo , Xu Chunming , Qi Bao , Li Ning , Rustgi Sachin , Zhou Hao , Han Fangpu , Jiang Jiming , von Wettstein Diter , Liu Bao
Published: February 2013

Allopolyploidization has been a driving force in plant evolution. Formation of common wheat (
Triticum aestivum
L.) represents a classic example of successful speciation via allopolyploidy. Nevertheless, the immediate chromosomal consequences of allopolyploidization in wheat remain largely unexplored. We report here an in-depth investigation on transgenerational chromosomal variation in resynthesized allohexaploid wheats that are identical in genome constitution to common wheat. We deployed sequential FISH, genomic in situ hybridization (GISH), and homeolog-specific pyrosequencing, which enabled unequivocal identification of each of the 21 homologous chromosome pairs in each of >1,000 individual plants from 16 independent lines. We report that whole-chromosome aneuploidy occurred ubiquitously in early generations (from selfed generation S
1
to >S
20
) of wheat allohexaploidy although at highly variable frequencies (20–100%). In contrast, other types of gross structural variations were scant. Aneuploidy included an unexpected hidden type, which had a euploid chromosome number of 2
n
= 42 but with simultaneous loss and gain of nonhomeologous chromosomes. Of the three constituent subgenomes, B showed the most lability for aneuploidy, followed by A, but the recently added D subgenome was largely stable in most of the studied lines. Chromosome loss and gain were also unequal across the 21 homologous chromosome pairs. Pedigree analysis showed no evidence for progressive karyotype stabilization even with multigenerational selection for euploidy. Profiling of two traits directly related to reproductive fitness showed that although pollen viability was generally reduced by aneuploidy, the adverse effect of aneuploidy on seed-set is dependent on both aneuploidy type and synthetic line.
Mechanical model of blebbing in nuclear lamin meshworks
Authors: Funkhouser Chloe M. , Sknepnek Rastko , Shimi Takeshi , Goldman Anne E. , Goldman Robert D. , Olvera de la Cruz Monica
Published: February 2013

Much of the structural stability of the nucleus comes from meshworks of intermediate filament proteins known as lamins forming the inner layer of the nuclear envelope called the nuclear lamina. These lamin meshworks additionally play a role in gene expression. Abnormalities in nuclear shape are associated with a variety of pathologies, including some forms of cancer and Hutchinson–Gilford Progeria Syndrome, and often include protruding structures termed nuclear blebs. These nuclear blebs are thought to be related to pathological gene expression; however, little is known about how and why blebs form. We have developed a minimal continuum elastic model of a lamin meshwork that we use to investigate which aspects of the meshwork could be responsible for bleb formation. Mammalian lamin meshworks consist of two types of lamin proteins, A type and B type, and it has been reported that nuclear blebs are enriched in A-type lamins. Our model treats each lamin type separately and thus, can assign them different properties. Nuclear blebs have been reported to be located in regions where the fibers in the lamin meshwork have a greater separation, and we find that this greater separation of fibers is an essential characteristic for generating nuclear blebs. The model produces structures with comparable morphologies and distributions of lamin types as real pathological nuclei. Thus, preventing this opening of the meshwork could be a route to prevent bleb formation, which could be used as a potential therapy for the pathologies associated with nuclear blebs.
Biofilm streamers cause catastrophic disruption of flow with consequences for environmental and medical systems
Authors: Drescher Knut , Shen Yi , Bassler Bonnie L. , Stone Howard A.
Published: February 2013

Biofilms are antibiotic-resistant, sessile bacterial communities that occupy most moist surfaces on Earth and cause chronic and medical device-associated infections. Despite their importance, basic information about biofilm dynamics in common ecological environments is lacking. Here, we demonstrate that flow through soil-like porous materials, industrial filters, and medical stents dramatically modifies the morphology of
Pseudomonas aeruginosa
biofilms to form 3D streamers, which, over time, bridge the spaces between obstacles and corners in nonuniform environments. We discovered that accumulation of surface-attached biofilm has little effect on flow through such environments, whereas biofilm streamers cause sudden and rapid clogging. We demonstrate that flow-induced shedding of extracellular matrix from surface-attached biofilms generates a sieve-like network that captures cells and other biomass, which add to the existing network, causing exponentially fast clogging independent of growth. These results suggest that biofilm streamers are ubiquitous in nature and strongly affect flow through porous materials in environmental, industrial, and medical systems.
Deglycosylation-dependent fluorescent proteins provide unique tools for the study of ER-associated degradation
Authors: Grotzke Jeff E. , Lu Qiao , Cresswell Peter
Published: February 2013

Endoplasmic reticulum–associated degradation (ERAD) is a constitutive process that identifies misfolded proteins in the ER and shuttles them to the cytosol, where they can be degraded by the proteasome. The accumulation of misfolded proteins can be catastrophic at both the cellular and organismal level. Although the players involved and mechanistic details of ERAD are being characterized, much remains to be learned. Because of the complexity of the pathway, experimental studies generally require labor-intensive biochemical techniques. Here, we report the development of a system to analyze ERAD based on mutants of split or intact Venus fluorescent protein for which fluorescence depends on enzymatic deglycosylation. We have generated variants that only become fluorescent when they are first glycosylated in the ER and subsequently deglycosylated after retrotranslocation into the cytosol. The E3 ubiquitin ligase HMG-coA reductase degradation 1 homolog (Hrd1) and, consistent with the demonstrated glycosylation/deglycosylation requirement, the cytosolic deglycosylating enzyme peptide:N′glycanase are both required for fluorescence. Furthermore, although these deglycosylation-dependent fluorescent proteins are themselves ERAD substrates, they can also be fused to additional ERAD substrates to interrogate substrate-specific pathways. To validate the system we performed a genomewide siRNA screen that successfully identified known ERAD factors such as Hrd1; homocysteine-inducible, endoplasmic reticulum stress-inducible, ubiquitin-like domain member 1 (HERP); sel-1 suppressor of lin-12-like (SEL1L); and p97. These tools should greatly facilitate the identification of ERAD components and investigation of the mechanisms involved in this critical pathway.
Human genome-wide RNAi screen reveals a role for nuclear pore proteins in poxvirus morphogenesis
Authors: Sivan Gilad , Martin Scott E. , Myers Timothy G. , Buehler Eugen , Szymczyk Krysia H. , Ormanoglu Pinar , Moss Bernard
Published: February 2013

Poxviruses are considered less dependent on host functions than other DNA viruses because of their cytoplasmic site of replication and large genomes, which encode enzymes for DNA and mRNA synthesis. Nevertheless, RNAi screens with two independent human genome-scale libraries have identified more than 500 candidate genes that significantly inhibited and a similar number that enhanced replication and spread of infectious vaccinia virus (VACV). Translational, ubiquitin-proteosome, and endoplasmic reticulum-to-Golgi transport functions, known to be important for VACV, were enriched in the siRNA-inhibiting group, and RNA polymerase II and associated functions were enriched in the siRNA-enhancing group. Additional findings, notably the inhibition of VACV spread by siRNAs to several nuclear pore genes, were unanticipated. Knockdown of nucleoporin 62 strongly inhibited viral morphogenesis, with only a modest effect on viral gene expression, recapitulating and providing insight into previous studies with enucleated cells.
The Link between Substance Use and Reproductive Health Service Utilization among Young US Women
Authors: Hall Kelli Stidham , Moreau Caroline , Trussell James
Published: February 2013

Background

The authors sought to investigate associations between young women's use of alcohol and other substances and their sexual and reproductive health (SRH) service utilization.

Methods

The authors used data from 4421 young women aged 15–24 years in the nationally representative study, National Survey of Family Growth, 2002–2008. The authors examined associations between frequency of tobacco, alcohol, marijuana, and illicit drug use and SRH service use in the past year using logistic regression.

Results

Over half (59%) of the young women used SRH services, including contraception (48%), gynecological examination (47%), and sexually transmitted infection (STI) testing/treatment (17%) services. Proportions of SRH service use increased with higher frequencies of substance use (all P values <.001); service use was particularly common among daily substance users (range: 72% of daily marijuana users to 83% of daily binge drinkers). In multivariable analyses, associations between substance and SRH service use varied by substance and service type: weekly marijuana (odds ratio [OR] = 2.5, 95% confidence interval [95% CI] = 1.4, 4.3, P = .002) and alcohol (OR = 1.7, 95% CI = 1.1, 2.4, P = .01) use were positively associated with gynecological service use. All substances were positively associated with STI service use. However, daily smoking was negatively associated with contraceptive service use (OR = 0.6, 95% CI = 0.4, 0.8, P = .001).

Conclusion

SRH service use was common among women reporting frequent substance use. SRH settings provide an opportunity to deliver substance use screening and preventive care to young women.
Cumulative and Non-Cumulative Semantic Interference in Object Naming: Evidence from Blocked and Continuous Manipulations of Semantic Context
Authors: Belke Eva , Stielow Anna
Published: February 2013

Experiments involving blocked and continuous manipulations of the semantic naming context demonstrate that, when speakers name several taxonomically related objects in close succession, they display persistent interference effects. A review of studies using the blocked paradigm shows that, unlike the continuous paradigm, it typically does not induce cumulative interference effects in healthy speakers. This contrasts with the simulation results obtained from a model of semantic context effects recently put forward by Oppenheim and colleagues [Oppenheim, G. M., Dell, G. S., & Schwartz, M. F. (2010). The dark side of incremental learning: A model of cumulative semantic interference during lexical access in speech production. Cognition, 114, 227–262], which generates cumulative effects in both paradigms. We propose that the effects are non-cumulative in the blocked paradigm, because it allows participants to bias top-down the levels of activation of lexical-semantic representations, thereby curtailing the accumulating interference. Indeed, prior research has shown that the interference effects in the blocked paradigm are exacerbated when participants carry out a concurrent digit-retention task, loading on working memory and reducing their capacity to exert a top-down bias. In Experiment 1, combining the continuous paradigm with a digit-retention task, we demonstrate that this does not exacerbate cumulative context effects, corroborating the selective role of working memory and the associated top-down biasing mechanism in the blocked paradigm. A review of neuropsychological and neuroimaging studies demonstrates that left inferior frontal regions may play a critical role in controlling semantic interference top-down. We discuss the implications of these findings for language production research and for models of lexical-semantic encoding.
The microtubule affinity regulating kinase MARK4 promotes axoneme extension during early ciliogenesis
Authors: Kuhns Stefanie , Schmidt Kerstin N. , Reymann Jürgen , Gilbert Daniel F. , Neuner Annett , Hub Birgit , Carvalho Ricardo , Wiedemann Philipp , Zentgraf Hanswalter , Erfle Holger , Klingmüller Ursula , Boutros Michael , Pereira Gislene
Published: February 2013

Despite the critical contributions of cilia to embryonic development and human health, key regulators of cilia formation await identification. In this paper, a functional RNA interference–based screen linked 30 novel protein kinases with ciliogenesis. Of them, we have studied the role of the microtubule (MT)-associated protein/MT affinity regulating kinase 4 (MARK4) in depth. MARK4 associated with the basal body and ciliary axoneme in human and murine cell lines. Ultrastructural and functional analyses established that MARK4 kinase activity was required for initiation of axoneme extension. We identified the mother centriolar protein ODF2 as an interaction partner of MARK4 and showed that ODF2 localization to the centriole partially depended on MARK4. Our data indicated that, upon MARK4 or ODF2 knockdown, the ciliary program arrested before the complete removal of the CP110–Cep97 inhibitory complex from the mother centriole, suggesting that these proteins act at this level of axonemal extension. We propose that MARK4 is a critical positive regulator of early steps in ciliogenesis.
Robust polarity establishment occurs via an endocytosis-based cortical corralling mechanism
Authors: Jose Mini , Tollis Sylvain , Nair Deepak , Sibarita Jean-Baptiste , McCusker Derek
Published: February 2013

Formation of a stable polarity axis underlies numerous biological processes. Here, using high-resolution imaging and complementary mathematical modeling we find that cell polarity can be established via the spatial coordination of opposing membrane trafficking activities: endocytosis and exocytosis. During polarity establishment in budding yeast, these antagonistic processes become apposed. Endocytic vesicles corral a central exocytic zone, tightening it to a vertex that establishes the polarity axis for the ensuing cell cycle. Concomitantly, the endocytic system reaches an equilibrium where internalization events occur at a constant frequency. Endocytic mutants that failed to initiate periodic internalization events within the corral displayed wide, unstable polarity axes. These results, predicted by in silico modeling and verified by high resolution in vivo studies, identify a requirement for endocytic corralling during robust polarity establishment.
Canonical Wnt signaling inhibits osteoclastogenesis independent of osteoprotegerin
Authors: Albers Joachim , Keller Johannes , Baranowsky Anke , Beil Frank Timo , Catala-Lehnen Philip , Schulze Jochen , Amling Michael , Schinke Thorsten
Published: February 2013

Although Wnt signaling is considered a key regulatory pathway for bone formation, inactivation of β-catenin in osteoblasts does not affect their activity but rather causes increased osteoclastogenesis due to insufficient production of osteoprotegerin (Opg). By monitoring the expression pattern of all known genes encoding Wnt receptors in mouse tissues and bone cells we identified Frizzled 8 (Fzd8) as a candidate regulator of bone remodeling. Fzd8-deficient mice displayed osteopenia with normal bone formation and increased osteoclastogenesis, but this phenotype was not associated with impaired Wnt signaling or Opg production by osteoblasts. The deduced direct negative influence of canonical Wnt signaling on osteoclastogenesis was confirmed in vitro and through the generation of mice lacking β-catenin in the osteoclast lineage. Here, we observed increased bone resorption despite normal Opg production and a resistance to the anti-osteoclastogenic effect of Wnt3a. These results demonstrate that Fzd8 and β-catenin negatively regulate osteoclast differentiation independent of osteoblasts and that canonical Wnt signaling controls bone resorption by two different mechanisms.
Condensin II initiates sister chromatid resolution during S phase
Authors: Ono Takao , Yamashita Daisuke , Hirano Tatsuya
Published: February 2013

Condensins I and II are multisubunit complexes that play essential yet distinct functions in chromosome condensation and segregation in mitosis. Unlike condensin I, condensin II localizes to the nucleus during interphase, but it remains poorly understood what functions condensin II might have before mitotic entry. Here, we report that condensin II changes its chromatin-binding property during S phase. Remarkably, advanced premature chromosome condensation (PCC) assays enabled us to visualize condensin II forming “sister axes” in replicated regions of chromosomes in S phase cells. Depletion of condensin II compromised PCC-driven sister chromatid resolution during S phase. Moreover, fluorescence in situ hybridization assays revealed that condensin II, but not condensin I, promotes disjoining duplicated chromosomal loci during S phase. Application of mild replicative stress partially impaired this process and further exacerbated phenotypes arising from condensin II depletion. Our results suggest that condensin II initiates structural reorganization of duplicated chromosomes during S phase to prepare for their proper condensation and segregation in mitosis.
Voltage-sensor movements describe slow inactivation of voltage-gated sodium channels II: A periodic paralysis mutation in NaV1.4 (L689I)
Authors: Silva Jonathan R. , Goldstein Steve A.N.
Published: February 2013

In skeletal muscle, slow inactivation (SI) of NaV1.4 voltage-gated sodium channels prevents spontaneous depolarization and fatigue. Inherited mutations in NaV1.4 that impair SI disrupt activity-induced regulation of channel availability and predispose patients to hyperkalemic periodic paralysis. In our companion paper in this issue (Silva and Goldstein. 2013. J. Gen. Physiol. http://dx.doi.org/10.1085/jgp.201210909), the four voltage sensors in NaV1.4 responsible for activation of channels over microseconds are shown to slowly immobilize over 1–160 s as SI develops and to regain mobility on recovery from SI. Individual sensor movements assessed via attached fluorescent probes are nonidentical in their voltage dependence, time course, and magnitude: DI and DII track SI onset, and DIII appears to reflect SI recovery. A causal link was inferred by tetrodotoxin (TTX) suppression of both SI onset and immobilization of DI and DII sensors. Here, the association of slow sensor immobilization and SI is verified by study of NaV1.4 channels with a hyperkalemic periodic paralysis mutation; L689I produces complex changes in SI, and these are found to manifest directly in altered sensor movements. L689I removes a component of SI with an intermediate time constant (∼10 s); the mutation also impedes immobilization of the DI and DII sensors over the same time domain in support of direct mechanistic linkage. A model that recapitulates SI attributes responsibility for intermediate SI to DI and DII (10 s) and a slow component to DIII (100 s), which accounts for residual SI, not impeded by L689I or TTX.
An example of compact Kähler manifold with nonnegative quadratic bisectional curvature
Authors: Li Qun , Wu Damin , Zheng Fangyang
Published: February 2013

We construct a compact Kähler manifold of nonnegative quadratic bisectional curvature which does not admit any Kähler metric of nonnegative orthogonal bisectional curvature. The manifold is a 7-dimensional Kähler

C
C

-space with second Betti number equal to 1, and its canonical metric is a Kähler-Einstein metric of positive scalar curvature.
LESION SIMULATING DISEASE1, ENHANCED DISEASE SUSCEPTIBILITY1, and PHYTOALEXIN DEFICIENT4 Conditionally Regulate Cellular Signaling Homeostasis, Photosynthesis, Water Use Efficiency, and Seed Yield in Arabidopsis
Authors: Wituszyńska Weronika , Ślesak Ireneusz , Vanderauwera Sandy , Szechyńska-Hebda Magdalena , Kornaś Andrzej , Van Der Kelen Katrien , Mühlenbock Per , Karpińska Barbara , Maćkowski Sebastian , Van Breusegem Frank , Karpiński Stanisław
Published: February 2013

There is growing evidence that for a comprehensive insight into the function of plant genes, it is crucial to assess their functionalities under a wide range of conditions. In this study, we examined the role of LESION SIMULATING DISEASE1 (LSD1), ENHANCED DISEASE SUSCEPTIBILITY1 (EDS1), and PHYTOALEXIN DEFICIENT4 (PAD4) in the regulation of photosynthesis, water use efficiency, reactive oxygen species/hormonal homeostasis, and seed yield in Arabidopsis (Arabidopsis thaliana) grown in the laboratory and in the field. We demonstrate that the LSD1 null mutant (lsd1), which is known to exhibit a runaway cell death in nonpermissive conditions, proves to be more tolerant to combined drought and high-light stress than the wild type. Moreover, depending on growing conditions, it shows variations in water use efficiency, salicylic acid and hydrogen peroxide concentrations, photosystem II maximum efficiency, and transcription profiles. However, despite these changes, lsd1 demonstrates similar seed yield under all tested conditions. All of these traits depend on EDS1 and PAD4. The differences in the pathways prevailing in the lsd1 in various growing environments are manifested by the significantly smaller number of transcripts deregulated in the field compared with the laboratory, with only 43 commonly regulated genes. Our data indicate that LSD1, EDS1, and PAD4 participate in the regulation of various molecular and physiological processes that influence Arabidopsis fitness. On the basis of these results, we emphasize that the function of such important regulators as LSD1, EDS1, and PAD4 should be studied not only under stable laboratory conditions, but also in the environment abounding in multiple stresses.
Time-Resolved Fluorescence Imaging Reveals Differential Interactions ofN-Glycan Processing Enzymes across the Golgi Stack in Planta
Authors: Schoberer Jennifer , Liebminger Eva , Botchway Stanley W. , Strasser Richard , Hawes Chris
Published: February 2013

N-Glycan processing is one of the most important cellular protein modifications in plants and as such is essential for plant development and defense mechanisms. The accuracy of Golgi-located processing steps is governed by the strict intra-Golgi localization of sequentially acting glycosidases and glycosyltransferases. Their differential distribution goes hand in hand with the compartmentalization of the Golgi stack into cis-, medial-, and trans-cisternae, which separate early from late processing steps. The mechanisms that direct differential enzyme concentration are still unknown, but the formation of multienzyme complexes is considered a feasible Golgi protein localization strategy. In this study, we used two-photon excitation-Förster resonance energy transfer-fluorescence lifetime imaging microscopy to determine the interaction of N-glycan processing enzymes with differential intra-Golgi locations. Following the coexpression of fluorescent protein-tagged amino-terminal Golgi-targeting sequences (cytoplasmic-transmembrane-stem [CTS] region) of enzyme pairs in leaves of tobacco (Nicotiana spp.), we observed that all tested cis- and medial-Golgi enzymes, namely Arabidopsis (Arabidopsis thaliana) Golgi α-mannosidase I, Nicotiana tabacum β1,2-N-acetylglucosaminyltransferase I, Arabidopsis Golgi α-mannosidase II (GMII), and Arabidopsis β1,2-xylosyltransferase, form homodimers and heterodimers, whereas among the late-acting enzymes Arabidopsis β1,3-galactosyltransferase1 (GALT1), Arabidopsis α1,4-fucosyltransferase, and Rattus norvegicus α2,6-sialyltransferase (a nonplant Golgi marker), only GALT1 and medial-Golgi GMII were found to form a heterodimer. Furthermore, the efficiency of energy transfer indicating the formation of interactions decreased considerably in a cis-to-trans fashion. The comparative fluorescence lifetime imaging of several full-length cis- and medial-Golgi enzymes and their respective catalytic domain-deleted CTS clones further suggested that the formation of protein-protein interactions can occur through their amino-terminal CTS region.
Chromoplast-Specific Carotenoid-Associated Protein Appears to Be Important for Enhanced Accumulation of Carotenoids inhp1Tomato Fruits
Authors: Kilambi Himabindu Vasuki , Kumar Rakesh , Sharma Rameshwar , Sreelakshmi Yellamaraju
Published: February 2013

Tomato (Solanum lycopersicum) high-pigment mutants with lesions in diverse loci such as DNA Damage-Binding Protein1 (high pigment1 [hp1]), Deetiolated1 (hp2), Zeaxanthin Epoxidase (hp3), and Intense pigment (Ip; gene product unknown) exhibit increased accumulation of fruit carotenoids coupled with an increase in chloroplast number and size. However, little is known about the underlying mechanisms exaggerating the carotenoid accumulation and the chloroplast number in these mutants. A comparison of proteome profiles from the outer pericarp of hp1 mutant and wild-type (cv Ailsa Craig) fruits at different developmental stages revealed at least 72 differentially expressed proteins during ripening. Hierarchical clustering grouped these proteins into three clusters. We found an increased abundance of chromoplast-specific carotenoid-associated protein (CHRC) in hp1 fruits at red-ripe stage that is also reflected in its transcript level. Western blotting using CHRC polyclonal antibody from bell pepper (Capsicum annuum) revealed a 2-fold increase in the abundance of CHRC protein in the red-ripe stage of hp1 fruits compared with the wild type. CHRC levels in hp2 were found to be similar to that of hp1, whereas hp3 and Ip showed intermediate levels to those in hp1, hp2, and wild-type fruits. Both CHRC and carotenoids were present in the isolated plastoglobules. Overall, our results suggest that loss of function of DDB1, DET1, Zeaxanthin Epoxidase, and Ip up-regulates CHRC levels. Increase in CHRC levels may contribute to the enhanced carotenoid content in these high-pigment fruits by assisting in the sequestration and stabilization of carotenoids.
The Anticipation of Danger: Microbe-Associated Molecular Pattern Perception Enhances AtPep-Triggered Oxidative Burst
Authors: Flury Pascale , Klauser Dominik , Schulze Birgit , Boller Thomas , Bartels Sebastian
Published: February 2013

The endogenous Arabidopsis (Arabidopsis thaliana) peptides, AtPeps, elicit an innate immune response reminiscent of pattern-triggered immunity. Detection of various danger signals, including microbe-associated molecular patterns (MAMPs), leads to elevated transcription of PROPEPs, the AtPep precursors, and PEPRs, the AtPep receptors. It has been hypothesized that AtPeps are involved in enhancing pattern-triggered immunity. Following this idea, we analyzed the relationship between MAMP- and AtPep-elicited signaling. We found that the perception of MAMPs enhanced a subsequent AtPep-triggered production of reactive oxygen species (ROS). Intriguingly, other components of AtPep-triggered immunity like Ca2+ influx, mitogen-activated protein kinase phosphorylation, ethylene production, and expression of early defense genes, as well as ROS-activated genes, remained unchanged. By contrast, treatment with methyl jasmonate promoted an increase of all analyzed AtPep-triggered responses. We positively correlated the intensities of generic AtPep-triggered responses with the abundance of the two AtPep receptors by generating constitutively expressing PEPR1 and PEPR2 transgenic lines and by analyzing pepr1 and pepr2 mutants. Further, we show that enhanced, as well as basal, ROS production triggered by AtPeps is absent in the double mutant of the respiratory burst oxidase homologs D and F (rbohD rbohF). We present evidence that the enhancement of AtPep-triggered ROS is not based on changes in the ROS detoxification machinery and is independent of mitogen-activated protein kinase and Ca2+ signaling pathways. Taken together, these results indicate an additional level of regulation besides receptor abundance for the RbohD/RbohF-dependent production of AtPep-elicited ROS, which is specifically operated by MAMP-triggered pathways.
Comparison of the effects of artificial and natural barriers on large African carnivores: Implications for interspecific relationships and connectivity
Authors: Cozzi Gabriele , Broekhuis Femke , McNutt J. Weldon , Schmid Bernhard
Published: February 2013

Physical barriers contribute to habitat fragmentation, influence species distribution and ranging behaviour, and impact long‐term population viability. Barrier permeability varies among species and can potentially impact the competitive balance within animal communities by differentially affecting co‐occurring species. The influence of barriers on the spatial distribution of species within whole communities has nonetheless received little attention.

During a 4‐year period, we studied the influence of a fence and rivers, two landscape features that potentially act as barriers on space use and ranging behaviour of lions Panthera leo, spotted hyenas Crocuta crocuta, African wild dogs Lycaon pictus and cheetahs Acinonyx jubatus in Northern Botswana. We compared the tendencies of these species to cross the barriers using data generated from GPS‐radio collars fitted to a total of 35 individuals. Barrier permeability was inferred by calculating the number of times animals crossed a barrier vs. the number of times they did not cross. Finally, based on our results, we produced a map of connectivity for the broader landscape system.

Permeability varied significantly between fence and rivers and among species. The fence represented an obstacle for lions (permeability = 7·2%), while it was considerably more permeable for hyenas (35·6%) and wild dogs and cheetahs (≥50%). In contrast, the rivers and associated floodplains were relatively permeable to lions (14·4%) while they represented a nearly impassable obstacle for the other species (<2%).

The aversion of lions to cross the fence resulted in a relatively lion‐free habitat patch on one side of the fence, which might provide a potential refuge for other species. For instance, the competitively inferior wild dogs used this refuge significantly more intensively than the side of the fence with a high presence of lions.

We showed that the influence of a barrier on the distribution of animals could potentially result in a broad‐scale modification of community structure and ecology within a guild of co‐occurring species. As habitat fragmentation increases, understanding the impact of barriers on species distributions is thus essential for the implementation of landscape‐scale management strategies, the development and maintenance of corridors and the enhancement of connectivity.
Top‐down control of prey increases with drying disturbance in ponds: a consequence of non‐consumptive interactions?
Authors: Greig Hamish S. , Wissinger Scott A. , McIntosh Angus R.
Published: February 2013

Biotic interactions are often expected to decrease in intensity as abiotic conditions become more stressful to organisms. However, in many cases, food‐web and habitat complexity also change with abiotic stress or disturbance, potentially altering patterns of species interactions across environmental gradients.

We used a combination of field assays and mesocosm experiments to investigate how disturbance from desiccation moderates top‐down control of prey by predators across a gradient of pond duration in New Zealand.

Field manipulations of predator abundance in ponds led to an unexpected decrease in the top‐down control of prey biomass by predatory invertebrates as pond duration increased (decreasing abiotic stress). Predatory fish, which are restricted to permanent ponds, had negligible effects on prey biomass. Mesocosm experiments further indicated the consumptive effects of fish are weak; a result that cannot be explained by an increase in physical habitat refugia in relatively more permanent ponds.

Manipulations of invertebrate predator diversity in mesocosms (both substitutive and additive treatments), and the addition of olfactory fish cues, revealed that strong non‐consumptive effects of fish reduced predation by predatory invertebrates, and these effects overwhelmed the positive influence of invertebrate predator diversity on prey consumption.

These results suggest that decreases in top‐down control with increasing pond permanence are likely a result of non‐consumptive effects of fish weakening predation by invertebrate predators in the more complex food webs of permanent ponds. Therefore, considering non‐consumptive effects of predators in complex food webs will likely improve the understanding of biotic interactions across environmental gradients.
Is restoring flora the same as restoring fauna? Lessons learned from koalas and mining rehabilitation
Authors: Cristescu Romane H. , Rhodes Jonathan , Frére Céline , Banks Peter B.
Published: February 2013

Rehabilitation of degraded and disturbed landscapes has become critical for counteracting habitat loss. The success of rehabilitation projects, to date, has focused on abiotic and flora‐based criteria of success, leaving fauna unmonitored. This follows from the common paradigm that if flora recovers, fauna will recover too. However, we know very little about the extent to which this assumption is true. We addressed this issue by examining whether flora criteria used to assess mine rehabilitation reflected patterns in the recovery of an iconic species, the koalaPhascolarctos cinereus, in eastern Australia.

We used rank tests to search for correlations between current mining flora criteria and fauna presence. We then developeda prioriregression models to search for new abiotic and flora criteria that are biologically relevant toPhascolarctos cinereus. In a third step, we investigated correlations between rehabilitation success ranked on the best biologically relevant habitat variables andPhascolarctos cinereusrecolonization.

We found that rehabilitation success based on current mining flora criteria (calculated at two different scales: rehabilitation blocks and monitoring plots) did not correlate withPhascolarctos cinereuspresence.

In contrast to the current flora‐based criteria, we found that variables that are biologically relevant toPhascolarctos cinereushad more influence on its presence. For instance, species richness in food trees favoured byPhascolarctos cinereusand tree canopy cover had a positive effect on its recolonization. However, correlations between biologically relevant habitat variables and fauna occurrence were still inconsistent.

Synthesis and applications. In our study, flora criteria for rehabilitation success did not correlate with fauna recolonization. We also found several additional difficulties in predicting fauna recolonization based on habitat variables, such as the choice of relevant scales and the geographic specificity of relevant variables. The choice between monitoring habitat proxies or fauna will ultimately be based on weighting costs and efficiency and will depend on the fauna species. However, we argue that in general, fauna species should be directly monitored to ensure the recolonization of i) species of interest (e.g. threatened and charismatic) and ii) fauna involved in long‐term resilience of ecosystems.