Retrograde signaling: Organelles go networking Kleine, Tatjana; Leister, Dario
Biochimica et biophysica acta,
August 2016, 2016-Aug, 2016-08-00, Letnik:
1857, Številka:
8
Journal Article
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The term retrograde signaling refers to the fact that chloroplasts and mitochondria utilize specific signaling molecules to convey information on their developmental and physiological states to the ...nucleus and modulate the expression of nuclear genes accordingly. Signals emanating from plastids have been associated with two main networks: ‘Biogenic control’ is active during early stages of chloroplast development, while ‘operational’ control functions in response to environmental fluctuations. Early work focused on the former and its major players, the GUN proteins. However, our view of retrograde signaling has since been extended and revised. Elements of several ‘operational’ signaling circuits have come to light, including metabolites, signaling cascades in the cytosol and transcription factors. Here, we review recent advances in the identification and characterization of retrograde signaling components. We place particular emphasis on the strategies employed to define signaling components, spanning the entire spectrum of genetic screens, metabolite profiling and bioinformatics. This article is part of a Special Issue entitled ‘EBEC 2016: 19th European Bioenergetics Conference, Riva del Garda, Italy, July 2–6, 2016’, edited by Prof. Paolo Bernardi.
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•Several novel components of retrograde signaling have been identified recently.•Strategies employed to define signaling components are highlighted.•Mitochondrial and chloroplast signaling share components.•Retrograde signaling recruited modules that probably evolved in other contexts.
Graphene-polymer nanocomposite coatings are used to improve upon the thermal conductivity of metallic substrates. Here we quantify the enhancement provided by coatings comprised of graphene nano ...platelets (GNPs) of aspect ratios 1, 1.25, 1.5, 1.75, and 2 and mass fractions 0.1, 0.3, and 0.5 either randomly distributed or aligned in one-direction in an epoxy matrix. We first find thermal conductivities, thermal expansion coefficient and the elastic moduli of the homogenized GNPs/matrix by using results of the 3-dimensional (3-D) deformations of the GNPs/matrix representative volumes analysed by the finite element method (FEM). These values are compared with those determined from the rule of mixtures, the inverse rule of mixtures, and the Halpin-Tsai equations. They are then used to analyse, by the FEM, 2-D uncoupled thermo-mechanical deformations of a stainless-steel plate coated with either a foulant (biofilm, aluminium oxide, magnesium carbonate, and calcium sulphate) or a thin GNPs/epoxy layer. It is found that the biofilm hinders most the heat exchange between the plate and its surroundings and the unidirectional oriented GNPs/epoxy coating the least. For the system studied, the compressive normal stress induced at the perfectly bonded interface between the coating and the steel plate can hinder delamination there.
Phototrophic polyhydroxyalkanoate (PHA) production is an emerging technology for recovering carbon and nutrients from diverse wastewater streams. However, reliable selection methods for the ...enrichment of PHA accumulating purple phototrophic bacteria (PPB) in phototrophic mixed cultures (PMC) are needed. This research evaluates the impact of ammonia on the selection of a PHA accumulating phototrophic-chemotrophic consortium, towards the enrichment of PHA accumulating PPB. The culture was operated under light-feast/dark-aerated-famine and winter simulated-outdoor conditions (13.2 ± 0.9 °C, transient light, 143.5 W/m
), using real fermented domestic wastewater with molasses as feedstock. Three ammonia supply strategies were assessed: 1) ammonia available only in the light phase, 2) ammonia always present and 3) ammonia available only during the dark-aerated-famine phase. Results showed that the PMC selected under 1) ammonia only in the light and 3) dark-famine ammonia conditions, presented the lowest PHA accumulation capacity during the light period (11.1 % g PHA/g VSS and 10.4 % g PHA/g VSS, respectively). In case 1), the absence of ammonia during the dark-aerated-famine phase did not promote the selection of PHA storing PPB, whereas in case 3) the absence of ammonia during the light period favoured cyanobacteria growth as well as purple sulphur bacteria with increased non-PHA inclusions, resulting in an overall decrease of phototrophic PHA accumulation capacity. The best PHA accumulation performance was obtained with selection under permanent presence of ammonia (case 2), which attained a PHA content of 21.6 % g PHA/g VSS (10.2 Cmmol PHA/L), at a production rate of 0.57 g PHA/L·day, during the light period in the selection reactor. Results in case 2 also showed that feedstock composition impacts the PMC performance, with feedstocks richer in more reduced volatile fatty acids (butyric and valeric acids) decreasing phototrophic performance and leading to acids entering the dark-aerated phase. Nevertheless, the presence of organic carbon in the aerated phase was not detrimental to the system. In fact, it led to the establishment of a phototrophic-chemotrophic consortium that could photosynthetically accumulate a PHA content of 13.2 % g PHA/g VSS (6.7 Cmmol PHA/L) at a production rate of 0.20 g PHA/L·day in the light phase, and was able to further increase that storage up to 18.5 % g PHA/g VSS (11.0 Cmmol PHA/L) at a production rate of 1.35 g PHA/L·day in the dark-aerated period. Furthermore, the light-feast/dark-aerated-famine operation was able to maintain the performance of the selection reactor under winter conditions, unlike non-aerated PMC systems operated under summer conditions, suggesting that night-time aeration coupled with the constant presence of ammonia can contribute to overcoming the seasonal constraints of outdoor operation of PMCs for PHA production.
•A new asymmetrical viscous damper (AVD) and asymmetrical dashpot (AD) model are proposed.•Setting AVD in parallel with tension-only brace (TOB) forms a TOB-AVD damping system.•The TOB-AVD decouples ...the damping and stiffness of the device.•The TOB-AVD dissipates seismic energy and eliminates the degradation phenomenon in the tension-only braced structures.
The stiffness and damping force are coupled in traditional damping devices for tension-only braced structures resulting in insufficient damping ability. A new asymmetrical viscous damper (AVD) is proposed which carries asymmetrical forces when it is tensed or compressed matching up with the tension-only brace (TOB). An uncoupled damping system of AVD setting in parallel with TOB, namely TOB-AVD is developed accordingly. The TOB-AVD can protect the tension-only braced structures from degraded slackness or straightened impulses under earthquake excitation. In this paper, an asymmetrical dashpot (AD) constitutive model is firstly proposed and implemented to the OpenSees platform. Secondly, based on combined type fluid viscous damper, two AVD samples representing the baseline and the improved one are designed, manufactured and tested. Finally, non-linear time history analysis is conducted on finite element models of a tension-only braced benchmark building with and without AVDs. The results indicate that while adopting TOB-AVD, the inter-story drift ratio, peak floor acceleration and floor acceleration amplification are reduced by 60.7%, 49.0% and 49.0% in average, eliminating the degradation phenomenon happening in TOBs and protecting both structural and non-structural components in tension-only braced structures.
Reactive nitrogen species (RNS) are formed when there is an abnormal increase in the level of nitric oxide (NO) produced by the inducible nitric oxide synthase (iNOS) and/or by the uncoupled ...endothelial nitric oxide synthase (eNOS). The presence of high concentrations of superoxide anions (O
) is also necessary for their formation. RNS react three times faster than O
with other molecules and have a longer mean half life. They cause irreversible damage to cell membranes, proteins, mitochondria, the endoplasmic reticulum, nucleic acids and enzymes, altering their activity and leading to necrosis and to cell death. Although nitrogen species are important in the redox imbalance, this review focuses on the alterations caused by the RNS in the cellular redox system that are associated with cardiometabolic diseases. Currently, nitrosative stress (NSS) is implied in the pathogenesis of many diseases. The mechanisms that produce damage remain poorly understood. In this paper, we summarize the current knowledge on the participation of NSS in the pathology of cardiometabolic diseases and their possible mechanisms of action. This information might be useful for the future proposal of anti-NSS therapies for cardiometabolic diseases.
We explore the use of uncoupled multi-core fibers employed for telecommunications as a technological platform for implementing polarization-based distributed twist sensors. Through ...polarimetric-optical frequency domain reflectometry we assess the twist-induced birefringence along the cores of an uncoupled four-core fiber. By applying controlled twist, we show that the elasto-optic coefficient in each core is consistent with the value reported for single-mode fibers, and that the cores experience the same birefringence variations in response to the applied twist. Moreover, we leverage the distinctive birefringence properties of unspun uncoupled multi-core fibers to achieve long-range twist sensing, showing that the measured twist is in excellent agreement with the applied one even when the perturbed fiber location is 500-m away from the source. We achieve a remarkable accuracy of 4 degrees in measuring the angle by which the fiber is twisted, with a spatial resolution of 8 cm. These results support the potential of uncoupled multi-core fibers to realize twist sensors that are relevant for applications such as umbilical cable monitoring.
In recent years, it has become evident that plants perceive, integrate and communicate abiotic stress signals through chloroplasts. During the process of acclimation plastid-derived, retrograde ...signals control nuclear gene expression in response to developmental and environmental cues leading to complex genetic and metabolic reprogramming to preserve cellular homeostasis under challenging environmental conditions. Upon stress-induced dysfunction of chloroplasts, GENOMES UNCOUPLED (GUN) proteins participate in the repression of
(
s). Here, we show that the retrograde signal emitted by, or communicated through, GUN-proteins is also essential to induce the accumulation of photoprotective anthocyanin pigments when chloroplast development is attenuated. Comparative whole transcriptome sequencing and genetic analysis reveal GUN1 and GUN5-dependent signals as a source for the regulation of genes involved in anthocyanin biosynthesis. The signal transduction cascade includes well-known transcription factors for the control of anthocyanin biosynthesis, which are deregulated in
mutants. We propose that regulation of
and genes contributing to anthocyanin biosynthesis are two, albeit oppositely, co-regulated processes during plastid biogenesis. This article is part of the theme issue 'Retrograde signalling from endosymbiotic organelles'.
In this letter, we address joint channel and power allocation in a device-to-device (D2D) network underlaying a cellular network in a time-varying environment. A fully distributed solution, which ...does not require information exchange, is proposed to allocate channel and power levels to D2D pairs while ensuring the quality of service (QoS) of the cellular user equipments (CUEs). The problem is modeled as a Stackelberg game with pricing. At the leader level, base station sets prices for the channels to ensure the QoS of the CUEs. At the follower level, D2D pairs use an uncoupled stochastic learning algorithm to learn the channel indices and power levels while minimizing the weighted aggregate interference and the price paid. The follower game is shown to be an ordinal potential game. We perform simulations to study the convergence of the algorithm.
Due to the huge property difference between high strength structural (HSS) steels and mild steels after welding, mechanical behavior and failure mode of fillet welded joints of HSS steels should be ...studied further. Numerical simulations can provide increased insight into this topic. This paper concerns finite element simulations of component tests of two types transverse fillet welded joints of HSS steels: lap-welded transverse fillet welds and cruciform type transverse fillet welds. In order to investigate the influences of triaxial stress states on fracture ductility of weld metals, a series of tests on specimens with various initial geometries are carried out. By comparing three typical uncoupled fracture models (stress triaxiality-dependent ductile fracture model (VGM), Lode angle-dependent ductile fracture model (MSSM) and combination of stress triaxiality and Lode angle ductile fracture model (BWM)), BWM gives precious prediction of ductile fracture of weld metals. The behaviors in terms of load-displacement and failure modes of transverse fillet welds are all well captured by the numerical simulations with calibrated ductile fracture models. Specifically, the location of fracture initiation and propagation of cracks obtained from simulations are both identical with real responses.
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•Effects of triaxial stress states on fracture ductility of weld metals are studied.•An uncoupled ductile fracture model for weld metals is adopted and calibrated.•Mechanical behavior of transverse fillet welded joints are simulated.
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