The heterotrimeric G-protein complex modulates light sensitivity in arabidopsis thaliana seed germination

Release of dormancy and induction of seed germination are complex traits finely regulated by hormonal signals and environmental cues such as temperature and light. The Red (R):Far-Red (FR) phytochrome photoreceptors mediate light regulation of seed germination. We investigated the possible involvement of heterotrimeric G-protein complex in the phytochrome signaling pathways of Arabidopsis thaliana seed germination. Germination rates of null mutants of the alpha (Gα) and beta (Gβ) subunits of the G-protein (Atgpa1-4 and agb1-2, respectively) and the double mutant (agb1-2/gpa1-4) are lower than the wildtype (WT) under continuous or pulsed light. The Gα and Gβ subunits play a role in seed germination under hourly pulses of R lower than 0.1 μmol m -2 s -1 whereas the Gβ subunit plays a role in higher R fluences. The germination of double mutants of G-protein subunits with phyA-211 and phyB-9 suggests that AtGPA1 seems to act as a positive regulator of phyA and probably phyB signaling pathways, while the role of AGB1 is ambiguous. The imbibition of seeds at 4°C and 35°C alters the R and FR light responsiveness of WT and G-protein mutants to a similar magnitude. Thus, Gα and Gβ subunits of the heterotrimeric G-protein complex modulate light induction of seed germination by phytochromes and are dispensable for the control of dormancy by low and high temperatures prior to irradiation. We discuss the possible indirect role of the G-protein complex on the phytochrome-regulated germination through hormonal signaling pathways.Fil: Botto, Javier Francisco. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura. Universidad de Buenos Aires. Facultad de Agronomía. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura; ArgentinaFil: Ibarra, Silvia Elizabeth. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura. Universidad de Buenos Aires. Facultad de Agronomía. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura; ArgentinaFil: Jones, Alan M.. University of North Carolina; Estados Unido

Multi-source data assimilation for physically based hydrological modeling of an experimental hillslope

Data assimilation has recently been the focus of much attention for integrated surface–subsurface hydrological models, whereby joint assimilation of water table, soil moisture, and river discharge measurements with the ensemble Kalman filter (EnKF) has been extensively applied. Although the EnKF has been specifically developed to deal with nonlinear models, integrated hydrological models based on the Richards equation still represent a challenge, due to strong nonlinearities that may significantly affect the filter performance. Thus, more studies are needed to investigate the capabilities of the EnKF to correct the system state and identify parameters in cases where the unsaturated zone dynamics are dominant, as well as to quantify possible tradeoffs associated with assimilation of multi-source data. Here, the CATHY (CATchment HYdrology) model is applied to reproduce the hydrological dynamics observed in an experimental two-layered hillslope, equipped with tensiometers, water content reflectometer probes, and tipping bucket flow gages to monitor the hillslope response to a series of artificial rainfall events. Pressure head, soil moisture, and subsurface outflow are assimilated with the EnKF in a number of scenarios and the challenges and issues arising from the assimilation of multi-source data in this real-world test case are discussed. Our results demonstrate that the EnKF is able to effectively correct states and parameters even in a real application characterized by strong nonlinearities. However, multi-source data assimilation may lead to significant tradeoffs: the assimilation of additional variables can lead to degradation of model predictions for other variables that are otherwise well reproduced. Furthermore, we show that integrated observations such as outflow discharge cannot compensate for the lack of well-distributed data in heterogeneous hillslopes.</p

Serum amyloid P aids complement-mediated immunity to Streptococcus pneumoniae

The physiological functions of the acute phase protein serum amyloid P (SAP) component are not well defined, although they are likely to be important, as no natural state of SAP deficiency has been reported. We have investigated the role of SAP for innate immunity to the important human pathogen Streptococcus pneumoniae. Using flow cytometry assays, we show that SAP binds to S. pneumoniae, increases classical pathway–dependent deposition of complement on the bacteria, and improves the efficiency of phagocytosis. As a consequence, in mouse models of infection, mice genetically engineered to be SAP-deficient had an impaired early inflammatory response to S. pneumoniae pneumonia and were unable to control bacterial replication, leading to the rapid development of fatal infection. Complement deposition, phagocytosis, and control of S. pneumoniae pneumonia were all improved by complementation with human SAP. These results demonstrate a novel and physiologically significant role for SAP for complement-mediated immunity against an important bacterial pathogen, and provide further evidence for the importance of the classical complement pathway for innate immunity

Dynamical transition in the TASEP with Langmuir kinetics: mean-field theory

We develop a mean-field theory for the totally asymmetric simple exclusion process (TASEP) with open boundaries, in order to investigate the so-called dynamical transition. The latter phenomenon appears as a singularity in the relaxation rate of the system toward its non-equilibrium steady state. In the high-density (low-density) phase, the relaxation rate becomes independent of the injection (extraction) rate, at a certain critical value of the parameter itself, and this transition is not accompanied by any qualitative change in the steady-state behavior. We characterize the relaxation rate by providing rigorous bounds, which become tight in the thermodynamic limit. These results are generalized to the TASEP with Langmuir kinetics, where particles can also bind to empty sites or unbind from occupied ones, in the symmetric case of equal binding/unbinding rates. The theory predicts a dynamical transition to occur in this case as well.Comment: 37 pages (including 16 appendix pages), 6 figures. Submitted to Journal of Physics

Substituent effects on the nitrogen-15 and carbon-13 shieldings of some N-arylguanidinium chlorides

The 13C and 15N chemical shifts of five N-arylguanidinium chlorides carrying polar substituents, ranging in character from 4-methoxy to 4-nitro groups, have been determined by NMR spectroscopy at the natural-abundance level of 13C and 15N in dimethyl sulfoxide solution. Comparison of the 13C shifts of these salts with those of monosubstituted benzenes shows that the guanidinium group induces an average downfield shift of -5.8 ppm of the resonance of the aryl carbon to which it is attached (C1), an average upfield shift of +4.2 ppm for C2 and C6, and a small upfield shift of +1.9 ppm for C4. The shifts of C3 and C5 are small and erratic relative to the corresponding carbons in monosubstituted benzenes. The 15N resonances of the guanidinium nitrogens are quite sensitive to electric effects resulting from substitution of polar groups at C4. The 15N shift of the ==NAr nitrogen relative to that of the salts suggests that the predominant tautomer for N-arylguanidines is (H2N)2C==NAr. The 15N shifts of the (NH2) 2 nitrogens correlate rather well with σp- parameters, whereas the shifts of the -NHAr nitrogens seem to correlate only with R values derived from the σp- substituent constants

Stretching of a capillary bridge featuring a particle-laden interface: particle sedimentation in the interface

This paper was presented at the 4th Micro and Nano Flows Conference (MNF2014), which was held at University College, London, UK. The conference was organised by Brunel University and supported by the Italian Union of Thermofluiddynamics, IPEM, the Process Intensification Network, the Institution of Mechanical Engineers, the Heat Transfer Society, HEXAG - the Heat Exchange Action Group, and the Energy Institute, ASME Press, LCN London Centre for Nanotechnology, UCL University College London, UCL Engineering, the International NanoScience Community, www.nanopaprika.eu.Colloidal particles adsorbed at fluid interfaces can be subject to external forces, for instance of magnetic, electrical, or gravitational origin. To develop a tool that will enable to study the effect of these forces on interfacial particle transport, we derive a transport equation for the surface particle concentration using the method of volume averaging. This equation is specialised to the problem of particle sedimentation induced by external forces on an axisymmetric capillary bridge stretched with assigned constant velocity between two circular plates. The equation for the interfacial concentration is one-way coupled to the unsteady Stokes equation in the capillary bridge, and solved in the thin-thread approximation, in the limit of small capillary and Bond numbers and for moderate area fractions. We find that owing to the competition between particle settling in one direction, and fluid velocity in the opposite direction, a concentration peak develops between the neck region and the moving plate. Hydrodynamic interactions, modelled through a concentration-dependent hindrance function, have the effect of steepening the shock-like concentration gradients that develop in the interface

Model and Design of a Power Driver for Piezoelectric Stack Actuators

A power driver has been developed to control piezoelectric stack actuators used in automotive application. A FEM model of the actuator has been implemented starting from experimental characterization of the stack and mechanical and piezoelectric parameters. Experimental results are reported to show a correct piezoelectric actuator driving method and the possibility to obtain a sensor-less positioning contro

El Curso de Ingreso como pasaje y como isla : Una vuelta de tuerca a la noción de "inclusión"

Fil: Botto, Malena. Universidad Nacional de La Plata. Facultad de Humanidades y Ciencias de la Educación; Argentina