Structure-based virtual screening identifies small-molecule inhibitors of O-fucosyltransferase SPINDLY in Arabidopsis.

Protein O-glycosylation is a nutrient signaling mechanism that plays an essential role in maintaining cellular homeostasis across different species. In plants, SPINDLY (SPY) and SECRET AGENT (SEC) posttranslationally modify hundreds of intracellular proteins with O-fucose and O-linked N-acetylglucosamine, respectively. SPY and SEC play overlapping roles in cellular regulation, and loss of both SPY and SEC causes embryo lethality in Arabidopsis (Arabidopsis thaliana). Using structure-based virtual screening of chemical libraries followed by in vitro and in planta assays, we identified a SPY O-fucosyltransferase inhibitor (SOFTI). Computational analyses predicted that SOFTI binds to the GDP-fucose-binding pocket of SPY and competitively inhibits GDP-fucose binding. In vitro assays confirmed that SOFTI interacts with SPY and inhibits its O-fucosyltransferase activity. Docking analysis identified additional SOFTI analogs that showed stronger inhibitory activities. SOFTI treatment of Arabidopsis seedlings decreased protein O-fucosylation and elicited phenotypes similar to the spy mutants, including early seed germination, increased root hair density, and defective sugar-dependent growth. In contrast, SOFTI did not visibly affect the spy mutant. Similarly, SOFTI inhibited the sugar-dependent growth of tomato (Solanum lycopersicum) seedlings. These results demonstrate that SOFTI is a specific SPY O-fucosyltransferase inhibitor that can be used as a chemical tool for functional studies of O-fucosylation and potentially for agricultural management.

Structure-based virtual screening identifies small molecule inhibitors of O-fucosyltransferase SPINDLY.

Protein O-glycosylation is a nutrient-signaling mechanism that plays essential roles in maintaining cellular homeostasis across different species. In plants, SPINDLY (SPY) and SECRET AGENT (SEC) catalyze posttranslational modifications of hundreds of intracellular proteins by O-fucose and O-linked N-acetylglucosamine, respectively. SPY and SEC play overlapping roles in cellular regulation and loss of both SPY and SEC causes embryo lethality in Arabidopsis. Using structure-based virtual screening of chemical libraries followed by in vitro and in planta assays, we identified a S PY O - f ucosyltransferase i nhibitor (SOFTI). Computational analyses predicted that SOFTI binds to the GDP-fucose-binding pocket of SPY and competitively inhibits GDP-fucose binding. In vitro assays confirmed that SOFTI interacts with SPY and inhibits its O-fucosyltransferase activity. Docking analysis identified additional SOFTI analogs that showed stronger inhibitory activities. SOFTI treatment of Arabidopsis seedlings decreased protein O-fucosylation and caused phenotypes similar to the spy mutants, including early seed germination, increased root hair density, and defect in sugar-dependent growth. By contrast, SOFTI had no visible effect on the spy mutant. Similarly, SOFTI inhibited sugar-dependent growth of tomato seedlings. These results demonstrate that SOFTI is a specific SPY O-fucosyltransferase inhibitor and a useful chemical tool for functional studies of O-fucosylation and potentially for agricultural management.

Microtopography mediates the climate-growth relationship and growth resilience to drought of Pinus tabulaeformis plantation in the hilly site.

Understanding the factors affecting the growth of plantation forests can reduce the loss of economic and ecological values caused by plantation forest subhealth. Plantation forests are widely distributed in hilly areas with microtopographic features. Microtopography influences climatic factors associated with plant growth, during not only general time but also extreme events like droughts. However, little research has been conducted on the effects of microtopography on the plantation forest growth. In this paper, we selected Pinus tabulaeformis planted in a hilly site, and studied the effect of microtopography on the climate-growth relationship and drought response of a typical plantation in Northeast China using dendroecological methods. We found: 1) Between hill positions, temperature caused a climatic growth difference. Compared to the hilltop, the correlation of annual growth on the hillside with monthly temperature was more negative in July-August and less positive in January-April. 2) Between aspects, precipitation intensities caused a climatic growth difference. Compared to the sunny slope, the correlation of annual growth on the shady slope with monthly total precipitation below 10 mm/day was less positive (May-June) or more negative (March-April and July), while that with monthly total precipitation above 10 mm/day was more positive in most months.3) Drought response varied significantly based on hill position and aspect. There was no significant difference in resistance between hill positions, while recovery and resilience on the hilltop were greater than those on the hillside.Resistance, recovery, and resilience were all lower on the sunny slope than those on the shady slope. Overall, microtopography exists the effects on the growth of plantation forests, both in terms of climate-growth relationships in general climate and in response to drought when extreme events. Meanwhile, the climatic factors that caused the difference in growth of plantation forests between hill positions and aspects differed. The difference in growth between hill positions was caused by temperature, while that between aspects was caused by precipitation intensity. Drought response difference reflected the legacy effect of drought on plantation growth, which could lead to subsequent changes in climate-growth relationships. These findings demonstrate that strengthening the research of forest trees on microtopography is necessary for accurate carbon sink assessment and precise forest management.

Cytokinin regulates apical hook development via the coordinated actions of EIN3/EIL1 and PIF transcription factors in Arabidopsis.

The apical hook is indispensable for protecting the delicate shoot apical meristem while dicot seedlings emerge from soil after germination in darkness. The development of the apical hook is co-ordinately regulated by multiple phytohormones and environmental factors. Yet, a holistic understanding of the spatial-temporal interactions between different phytohormones and environmental factors remains to be achieved. Using a chemical genetic approach, we identified kinetin riboside, as a proxy of kinetin, which promotes apical hook development of Arabidopsis thaliana in a partially ethylene-signaling-independent pathway. Further genetic and biochemical analysis revealed that cytokinin is able to regulate apical hook development via post-transcriptional regulation of the PHYTOCHROME INTERACTING FACTORs (PIFs), together with its canonical roles in inducing ethylene biosynthesis. Dynamic observations of apical hook development processes showed that ETHYLENE INSENSITVE3 (EIN3) and EIN3-LIKE1 (EIL1) are necessary for the exaggeration of hook curvature in response to cytokinin, while PIFs are crucial for the cytokinin-induced maintenance of hook curvature in darkness. Furthermore, these two families of transcription factors display divergent roles in light-triggered hook opening. Our findings reveal that cytokinin integrates ethylene signaling and light signaling via EIN3/EIL1 and PIFs, respectively, to dynamically regulate apical hook development during early seedling development.

Athermal repair of nanoscale defects in optical materials using a femtosecond laser.

Ion implantation is widely used to fabricate advanced optical and optoelectronic materials and devices. However, nanoscale defects generated during the ion implantation process severely affect the quality and properties of the material and device. Here, combining computational simulations and experiments, we investigate the mechanism for defect repair in fused silica after Cu ion implantation using femtosecond laser irradiation with an energy fluence much lower than the ablation threshold. Atomic force microscopy demonstrates no unexpected ablation. The optical absorption spectra show that various types of defects with formation energies between 1.9 and 6.2 eV can be repaired successfully via an athermal procedure. The Raman spectra imply that the broken chemical bonds reconnect after femtosecond laser irradiation. Our study reveals that low-energy femtosecond laser irradiation can transfer the appropriate energy needed to repair defects; thus it could be useful in fabricating nonlinear optical devices due to its high spatial selectivity and convenience.

[Improvement of cardiac function by recombinant adenovirus Ad-hBNP in rats with chronic heart failure].

OBJECTIVE: To evaluate the therapeutic effect of hBNP on rats with chronic heart failure (CHF). METHODS: Thirty CHF rats defined by echocardiography at 12 weeks post abdominal aortic constriction were randomly divided into Ad-hBNP group (2.5 × 10(10) VP/ml NS Ad-hBNP 1 ml/week × 4, n = 14), Ad-Track group (n = 8), placebo group (NS, n = 8), 10 sham-operated rats served as control group. After 4 weeks treatment, cardiac function was evaluated by echocardiography and hemodynamic measurements. Heart weight (HW) and HW/body weight (BW) ratio were determined. RESULTS: IVS, LVPW, LVEDD and LVESD were significantly reduced in the Ad-hBNP group [(2.34 ± 0.29) mm, (2.28 ± 0.18) mm, (6.50 ± 0.42) mm, (3.54 ± 0.59) mm] than those in the Ad-Track group [(2.71 ± 0.35) mm, (3.02 ± 0.85) mm, (7.71 ± 0.83) mm, (4.72 ± 0.80) mm] and in the NS group [(2.78 ± 0.23) mm, (2.83 ± 0.53) mm, (7.34 ± 0.97) mm, (4.55 ± 0.77) mm, all P < 0.05]. The LVEF and LVFS of the Ad-hBNP group [(79.27 ± 7.01)%, (43.38 ± 6.73)%] were significantly higher than in the Ad-Track group [(70.85 ± 4.81)%, (35.72 ± 3.68)%] and in the NS group [(69.67 ± 6.90)%, (34.91 ± 5.10)%, all P < 0.01]. HR [(417.48 ± 32.57) beats/min, (446.85 ± 61.49) beats/min, P < 0.05; (440.83 ± 32.18) beats/min, P < 0.05], LVEDP [(-4.24 ± 4.00) mm Hg (1 mm Hg = 0.133 kPa); (21.99 ± 6.80) mm Hg, P < 0.01; (18.00 ± 12.25) mm Hg, P < 0.01] were significantly decreased and while LVSP [(131.79 ± 15.76) mm Hg; (112.99 ± 32.35) mm Hg, P < 0.05; (117.13 ± 15.26) mm Hg], +dP/dt(max) [(5037.20 ± 430.41) mm Hg/s; (4217.40 ± 1354.15) mm Hg/s, P < 0.05; (4310.50 ± 1293.97) mm Hg/s, P < 0.05] and -dP/dt(max) [(-4382.00 ± 1304.79) mm Hg/s; (-3725.00 ± 791.34) mm Hg/s, P < 0.05; (-3890.00 ± 1043.73) mm Hg/s, P < 0.05]were significantly increased in Ad-hBNP group than in Ad-Track group and NS group (all P < 0.05). HW and HW/BW were also decreased in Ad-hBNP group than in the Ad-Track group and the NS group. CONCLUSION: Exogenous hBNP improved the cardiac function and attenuated remodeling in CHF rats.

Anisotropic in-plane spin splitting in an asymmetric (001) GaAs/AlGaAs quantum well.

The in-plane spin splitting of conduction-band electron has been investigated in an asymmetric (001) GaAs/AlxGa1-xAs quantum well by time-resolved Kerr rotation technique under a transverse magnetic field. The distinctive anisotropy of the spin splitting was observed while the temperature is below approximately 200 K. This anisotropy emerges from the combined effect of Dresselhaus spin-orbit coupling plus asymmetric potential gradients. We also exploit the temperature dependence of spin-splitting energy. Both the anisotropy of spin splitting and the in-plane effective g-factor decrease with increasing temperature.PACS: 78.47.jm, 71.70.Ej, 75.75.+a, 72.25.Fe.

Beam conditions for radiation generated by an electromagnetic J0-correlated Schell-model source.

Based on the 2x2 (electric field) cross-spectral density matrix, a model for an electromagnetic J0-correlated Schell-model beam is given that is a generalization of the scalar J0-correlated Schell-model beam. The conditions that the matrix for the source to generate an electromagnetic J0-correlated Schell-model beam are obtained. The condition for the source to generate a scalar J0-correlated Schell-model beam can be considered as a special case.

Stable pulse-compressed acousto-optic Q-switched fiber laser.

A novel acousto-optic switch operation by a simple laser-diode pumped acousto-optic, Q-switched, ytterbium-doped, double-clad fiber laser is reported. Stable compressed Q-switched sub-40 ns pulses with a beam quality factor (M(2)=2) are achieved at the repetition rate of 1-50 kHz. Q-switched pulses of ~20 microJ pulse energy and 35 ns pulse width are obtained at the repetition rate of 50 kHz. Finally, a reasonable explanation of the novel Q-switched operation is presented.

Compression of pulse duration in a laser-diode, end-pumped, double Q-switched laser.

By considering the Guassian transversal distribution of intracavity photon density and the longitudinal distribution of photon density along the cavity axis as well as the influence of the turn-off time of the acousto-optic Q switch, we introduce the coupled rate equations of a laser-diode, end-pumped, double Q-switched laser with an acousto-optic modulator and GaAs saturable absorber. In addition the thermal effect of the gain medium is taken into account. These coupled rate equations are solved numerically, and the dependence of pulse width on incident pump power at different pulse repetition rates is obtained for the generated output pulses. It is shown that the pulse duration is obviously shorter in contrast to the actively Q-switched Nd:YVO4 laser with an acoustic-optic modulator, and the maximum compression ratio of the pulse width is more than 60%. In the experiment a laser-diode, end-pumped, double Q-switched Nd:YVO4 laser with both an acousto-optic modulator and GaAs is realized, and the experimental results agree with the numerical solutions.