The nitrogen-sink is involved in the regulation of nitrogenase activity in white clover after defoliation

The objective of the present study was to develop an empirical cold hardiness model applicable to several taxa of deciduous trees. Cold hardiness expressed as lowest survival temperature of Acer rubrum, Betula nigra, Liquidambar styracifiua, Fraxinus pennsylvanica, Prunus serotina and Quercus alba was evaluated at approximately weekly intervals during the winters of three consecutive years. Plant samples and meteorological data were collected from Georgia Experiment Station, Griffin, Georgia. Maximum, minimum and average temperatures, hourly chill and heat accumulation. day length and time of year were used as input variables for model development. The statistical method of stepwise procedure of regression analysis was employed to select variables for the model. Based on the assumption that model components should be the same for all taxa included in this study and all three winters, the following independent model variables were selected as valid inputs: day length, number of accumulated hours with temperature above 20°C and number of accumulated hours with temperature below 10°C. Equation coefficients of species-specific models were determined for each species. Cold hardiness predictions were compared to actual observations for each species. The model components were interpreted as representing two processes: (1) internally regulated and independent of actual temperature, and (2) externally regulated and dependent on the amount of accumulated chill or heat. The model allowed for comparisons of cold hardening and dehardening between the studied taxa and between years.     

Ultrasonography of the omasum in 30 Saanen goats

Background  

Primary diseases of the omasum are uncommon in goats, although the omasum may be involved in various gastrointestinal disorders. Examination of the caprine omasum via ultrasonography requires a good understanding of the normal appearance of the organ. However, in contrast to cattle, there is a lack of reference information on this topic in goats. Thus, the goal of the present study was to describe the results of ultrasonography of the omasum in 30 healthy Saanen goats.     

Correction to: Mechanical factors contributing to the Venus flytrap’s rate-dependent response to stimuli

The sensory hairs of the Venus flytrap (Dionaea muscipula Ellis) detect mechanical stimuli imparted by their prey and fire bursts of electrical signals called action potentials (APs). APs are elicited when the hairs are sufficiently stimulated and two consecutive APs can trigger closure of the trap. Earlier experiments have identified thresholds for the relevant stimulus parameters, namely the angular displacement \(\theta \) and angular velocity \(\omega \). However, these experiments could not trace the deformation of the trigger hair’s sensory cells, which are known to transduce the mechanical stimulus. To understand the kinematics at the cellular level, we investigate the role of two relevant mechanical phenomena: viscoelasticity and intercellular fluid transport using a multi-scale numerical model of the sensory hair. We hypothesize that the combined influence of these two phenomena and \(\omega \) contribute to the flytrap’s rate-dependent response to stimuli. In this study, we firstly perform sustained deflection tests on the hair to estimate the viscoelastic material properties of the tissue. Thereafter, through simulations of hair deflection tests at different loading rates, we were able to establish a multi-scale kinematic link between \(\omega \) and the cell wall stretch \(\delta \). Furthermore, we find that the rate at which \(\delta \) evolves during a stimulus is also proportional to \(\omega \). This suggests that mechanosensitive ion channels, expected to be stretch-activated and localized in the plasma membrane of the sensory cells, could be additionally sensitive to the rate at which stretch is applied.

     

Recombinant Nup153 Incorporates in Vivo into Xenopus Oocyte Nuclear Pore Complexes

Nup153 is a molecular constituent of the nuclear basket of the nuclear pore complex (NPC) that plays a critical role in nuclear export of RNAs and proteins. In an effort to map this nucleoporin more precisely within the nuclear basket we have developed an experimental approach for localizing Nup153 expressed and incorporated in vivo into Xenopus oocyte NPCs. This approach involves the microinjection into the cytoplasm of Xenopus oocytes of in vitro synthesized mRNA from a vector encoding an epitope-tagged cDNA. Here we present results obtained by Western blots, fluorescence microscopy, and immuno-electron microscopy, which clearly document that the heterologous protein is properly expressed, targeted, and incorporated into preexisting Xenopus NPCs. This new approach for localizing nucleoporins within the structure of the NPC overcomes limitations of previous techniques and allows for greater specificity and resolution than have been possible with previous methods.     

The Polycomb group protein MEDEA controls cell proliferation and embryonic patterning in Arabidopsis

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Combined HDAC1 and HDAC2 Depletion Promotes Retinal Ganglion Cell Survival After Injury Through Reduction of p53 Target Gene Expression

Histones deacetylases (HDACs), besides their function as epigenetic regulators, deacetylate and critically regulate the activity of nonhistone targets. In particular, HDACs control partially the proapoptotic activity of p53 by balancing its acetylation state. HDAC inhibitors have revealed neuroprotective properties in different models, but the exact mechanisms of action remain poorly understood. We have generated a conditional knockout mouse model targeting retinal ganglion cells (RGCs) to investigate specifically the functional role of HDAC1 and HDAC2 in an acute model of optic nerve injury. Our results demonstrate that combined HDAC1 and HDAC2 ablation promotes survival of axotomized RGCs. Based on global gene expression analyses, we identified the p53-PUMA apoptosis-inducing axis to be strongly activated in axotomized mouse RGCs. Specific HDAC1/2 ablation inhibited this apoptotic pathway by impairing the crucial acetylation status of p53 and reducing PUMA expression, thereby contributing to the ensuing enhanced neuroprotection due to HDAC1/2 depletion. HDAC1/2 inhibition and the affected downstream signaling components emerge as specific targets for developing therapeutic strategies in neuroprotection.