909 research outputs found
A Methyl Esterase 1 (PvMES1) Promotes the Salicylic Acid Pathway and Enhances Fusarium Wilt Resistance in Common Beans
Common bean (Phaseolus vulgaris L.) is an important food legume. Fusarium wilt caused by Fusarium oxysporum f. sp. phaseoli is one of the most serious soil-born diseases of common bean found throughout the world and affects the yield and quality of the crop. Few sources of Fusarium wilt resistance exist in legumes and most are of quantitative inheritance. In this study, we have identified a methyl salicylate esterase (MES), PvMES1, that contributes to plant defense response by regulating the salicylic acid (SA) mediated signaling pathway in response to Fusarium wilt in common beans. The result showed the role of PvMES1 in regulating SA levels in common bean and thus the SA signaling pathway and defense response mechanism in the plant. Overexpression of the PvMES1 gene enhanced Fusarium wilt resistance; while silencing of the gene caused susceptibility to the diseases. RNA-seq analysis with these transiently modified plants showed that genes related to SA level changes included the following gene ontologies: a) interaction between host and pathogen; b) phenylpropanoid synthesis; and c) sugar metabolism as well as others. These key signal elements activated the defense response pathway in common bean to Fusarium wilt. Collectively, our findings indicate that PvMES1 plays a pivotal role in regulating SA biosynthesis and signaling, and increasing Fusarium wilt resistance in common bean, thus providing novel insight into the practical applications of both SA and MES genes and pathways they contribiute to for developing elite crop varieties with enhanced broad-spectrum resistance to this critical disease
ROSAT/ASCA Observations of a Serendipitous BL Lac Object PKS 2316-423: The Variable High-Energy Tail of Synchrotron Radiation
We present the analysis of archival data from ROSAT and ASCA of a
serendipitous BL Lac object PKS 2316-423. Because of its featureless
non-thermal radio/optical continuum, PKS 2316-423 has been called as a BL Lac
candidate in the literature. PKS 2316-423 was evidently variable over the
multiple X-ray observations, in particular, a variable high-energy tail of the
synchrotron radiation is revealed. The X-ray spectral analysis provides further
evidence of the synchrotron nature of its broad-band spectrum: a steep and
downward curving spectrum between 0.1--10 keV, typical of high-energy peaked BL
Lacs (HBL). The spectral energy distribution (SED) through radio-to-X-ray
yields the synchrotron radiation peak at frequency Vp=7.3 10^{15} Hz, with
integrated luminosity of Lsyn=2.1 10^{44} ergs s^{-1}. The averaged SED
properties of PKS 2316-423 are very similar to those ``intermediate'' BL Lac
objects (IBL) found recently in several deep surveys, such as Deep X-ray Radio
Blazar, Radio-Emitting X-ray, and ROSAT-Green Bank surveys. We suggest that PKS
2316-423 is an IBL though it also shows some general features of a HBL.
Actually, this double attribute of PKS 2316-423 provides a good test of the
prediction that an IBL object can show either synchrotron or inverse-Compton
characteristics in different variability states.Comment: 12 pages, including 4 figures, to appear in ApJ, 2000 July 2
A Systematic Analysis of Fe II Emission in Quasars: Evidence for Inflow to the Central Black Hole
Broad Fe II emission is a prominent feature of the optical and ultraviolet
spectra of quasars. We report on a systematical investigation of optical Fe II
emission in a large sample of 4037 z < 0.8 quasars selected from the Sloan
Digital Sky Survey. We have developed and tested a detailed line-fitting
technique, taking into account the complex continuum and narrow and broad
emission-line spectrum. Our primary goal is to quantify the velocity broadening
and velocity shift of the Fe II spectrum in order to constrain the location of
the Fe II-emitting region and its relation to the broad-line region. We find
that the majority of quasars show Fe II emission that is redshifted, typically
by ~ 400 km/s but up to 2000 km/s, with respect to the systemic velocity of the
narrow-line region or of the conventional broad-line region as traced by the
Hbeta line. Moreover, the line width of Fe II is significantly narrower than
that of the broad component of Hbeta. We show that the magnitude of the Fe II
redshift correlates inversely with the Eddington ratio, and that there is a
tendency for sources with redshifted Fe II emission to show red asymmetry in
the Hbeta line. These characteristics strongly suggest that Fe II originates
from a location different from, and most likely exterior to, the region that
produces most of Hbeta. The Fe II-emitting zone traces a portion of the
broad-line region of intermediate velocities whose dynamics may be dominated by
infall.Comment: 20 pages, 14 figures, accepted for publication in Ap
Hairy root transgene expression analysis of a secretory peroxidase (PvPOX1) from common bean infected by Fusarium wilt
Plant peroxidases (POXs) are one of the most important redox enzymes in the defense responses. However, the large number of different plant POX genes makes it necessary to carefully confirm the function of each paralogous POX gene in specific tissues and disease interactions. Fusarium wilt is a devastating disease of common bean caused by Fusarium oxysporum f. sp. phaseoli. In this study, we evaluated a peroxidase gene, PvPOX1, from a resistant common bean genotype, CAAS260205 and provided direct evidence for PvPOX1âs role in resistance by transforming the resistant allele into a susceptible common bean genotype, BRB130, via hairy root transformation using Agrobacterium rhizogenes. Analysis of PvPOX1 gene over-expressing hairy roots showed it increased resistance to Fusarium wilt both in the roots and the rest of transgenic plants. Meanwhile, the PvPOX1 expressive level, the peroxidase activity and hydrogen peroxide (H2O2) accumulation were also enhanced in the interaction. The result showed that the PvPOX1 gene played an essential role in Fusarium wilt resistance through the occurrence of reactive oxygen species (ROS) induced hypersensitive response. Therefore, PvPOX1 expression was proven to be a valuable gene for further analysis which can strengthen host defense response against Fusarium wilt through a ROS activated resistance mechanism
Restudy on Dark Matter Time-Evolution in the Littlest Higgs model with T-parity
Following previous study, in the Littlest Higgs model (LHM), the heavy photon
is supposed to be a possible dark matter candidate and its relic abundance of
the heavy photon is estimated in terms of the Boltzman-Lee-Weinberg
time-evolution equation. The effects of the T-parity violation is also
considered. Our calculations show that when Higgs mass taken to be 300
GeV and don't consider T-parity violation, only two narrow ranges
GeV and GeV are tolerable with the
current astrophysical observation and if GeV, there must at
least exist another species of heavy particle contributing to the cold dark
matter. As long as the T-parity can be violated, the heavy photon can decay
into regular standard model particles and would affect the dark matter
abundance in the universe, we discuss the constraint on the T-parity violation
parameter based on the present data. Direct detection prospects are also
discussed in some detail.Comment: 13 pages, 11 figures include
Evidence for electron-electron interaction in topological insulator thin films
We consider in our work high quality single crystal thin films of Bi2Se3,
grown by molecular beam epitaxy, both with and without Pb doping. Our ARPES
data demonstrate topological surface states with a Fermi level lying inside the
bulk band gap in the Pb doped filims. Transport data show weak localization
behavior, as expected for a 2D system, but a detailed analysis within the
standard theoretical framework of diffusive transport shows that the
temperature and magnetic field dependences of resistance cannot be reconciled
in a theory that neglects inter-electron interactions. We demonstrate that an
excellent account of quantum corrections to conductivity is achieved when both
disorder and interaction are taken into account. These results clearly
demonstrate that it is crucial to include electron electron interaction for a
comprehensive understanding of diffusive transport in topological insulators.Comment: Submitted to Phys. Rev.
Global climate damage in 2°C and 1.5°C scenarios based on BCC_SESM model in IAM framework
The quantitative functions for climate damages provide theoretical ground for the cost-benefit analysis in climate change economics, and they are also critical for linking climate module with economic module in the Integrated Assessment Models (IAMs). Nevertheless, it is necessary for IAMs to update sectoral climate impacts in order to catch up the advance in climate change studies. This study updates the sectoral climate damage function at global scale from climate Framework for Uncertainty, Negotiation and Distribution (FUND) model and develops the aggregate climate damage function in a bottom-up fashion. Besides conventional sectors such as agriculture, forestry, water resources, energy consumption and ecosystems, this study expands climate disaster types, assesses human health impacts caused by various air pollutants, and updates coastal damage by sea level rise. The Beijing Climate Center Simple Earth System Model (BCC_SESM) is used to project climate system based on Business-as-Usual (BAU) scenario, and the 2 °C and 1.5 °C scenarios based on RCPs and SSP2 databases. Sectoral results show that the agricultural sector is projected to suffer 63% of the total damage, followed by water resources (16%) and human health (12%) sectors in 2100. The regression results indicate that the aggregate climate damage function is in positive quadratic form. Under BAU scenario, the aggregate climate damage is projected to be 517.7 trillion USD during 2011â2100. Compared to that, the 2°C and 1.5°C scenarios are projected to respectively reduce climate damages by 215.6 trillion USD (approximately 41.6%) and 263.5 trillion USD (50.9%) in 2011â2100
ab initio modeling of open systems: charge transfer, electron conduction, and molecular switching of a C_{60} device
We present an {\it ab initio} analysis of electron conduction through a
molecular device. Charge transfer from the device electrodes to the
molecular region is found to play a crucial role in aligning the lowest
unoccupied molecular orbital (LUMO) of the to the Fermi level of the
electrodes. This alignment induces a substantial device conductance of . A gate potential can inhibit charge transfer and
introduce a conductance gap near , changing the current-voltage
characteristics from metallic to semi-conducting, thereby producing a field
effect molecular current switch
(Z)3,4,5,4'-trans-tetramethoxystilbene, a new analogue of resveratrol, inhibits gefitinb-resistant non-small cell lung cancer via selectively elevating intracellular calcium level.
Calcium is a second messenger which is required for regulation of many cellular processes. However, excessive elevation or prolonged activation of calcium signaling would lead to cell death. As such, selectively regulating calcium signaling could be an alternative approach for anti-cancer therapy. Recently, we have identified an effective analogue of resveratrol, (Z)3,4,5,4âČ-trans-tetramethoxystilbene (TMS) which selectively elevated the intracellular calcium level in gefitinib-resistant (G-R) non-small-cell lung cancer (NSCLC) cells. TMS exhibited significant inhibitory effect on G-R NSCLC cells, but not other NSCLC cells and normal lung epithelial cells. The phosphorylation and activation of EGFR were inhibited by TMS in G-R cells. TMS induced caspase-independent apoptosis and autophagy by directly binding to SERCA and causing endoplasmic reticulum (ER) stress and AMPK activation. Proteomics analysis also further confirmed that mTOR pathway, which is the downstream of AMPK, was significantly suppressed by TMS. JNK, the cross-linker of ER stress and mTOR pathway was significantly activated by TMS. In addition, the inhibition of JNK activation can partially block the effect of TMS. Taken together, TMS showed promising anti-cancer activity by mediating calcium signaling pathway and inducing apoptosis as well as autophagy in G-R NSCLC cells, providing strategy in designing multi-targeting drug for treating G-R patients
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