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- Aromatic amino acids (1)
- AtD-CGS (1)
- Branched chain amino acids (1)
- CYSTATHIONINE GAMMA-SYNTHASE (1)
- Glutathione (1)
- Oryza sativa ssp japonica cv. taipei 309 (1)
- Sulfate (1)
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An important goal of rice cultivar development is improvement of protein quality, especially with respect to essential amino acids such as methionine. With the goal of increasing seed methionine content, we generated Oryza sativa ssp. japonica cv. Taipei 309 transgenic lines expressing a feedback-desensitized CYSTATHIONINE GAMMA-SYNTHASE from Arabidopsis thaliana (AtD-CGS) under the control of the maize ubiquitin promoter. Despite persistently elevated cystathionine gamma-synthase (CGS) activity in the AtD-CGS transgenic lines relative to untransformed Taipei, sulfate was the only sulfur-containing compound found to be elevated throughout vegetative development. Accumulation of methionine and other sulfur-containing metabolites was limited to the leaves of young plants. Sulfate concentration was found to strongly and positively correlate with CGS activity across vegetative development, irrespective of whether the activity was provided by the endogenous rice CGS or by a combination of endogenous and AtD-CGS. Conversely, the concentrations of glutathione, valine, and leucine were clearly negatively correlated with CGS activity in the same tissues. We also observed a strong decrease in CGS activity in both untransformed Taipei and the AtD-CGS transgenic lines as the plants approached heading stage. The mechanism for this downregulation is currently unknown and of potential importance for efforts to increase methionine content in rice.
Reconstructing how rivers respond to changes in runoff or sediment supply by incising or aggrading has been pivotal in gauging the role of the Indian Summer Monsoon (ISM) as a geomorphic driver in the Himalayas. Here we present new chronological data for fluvial aggradation and incision from the Donga alluvial fan and the upper Alaknanda River, as well as a compilation of previous work. In addition to conventional OSL-SAR (Single-Aliquot Regenerative-Dose) dating method, we have tested and applied pulsed OSL (POSL) dating for quartz samples that include K-rich feldspar inclusions, which is expected to improve the applicability and validity of OSL ages in the Lesser Himalaya. For previously dated deposits, our OSL ages are shown to be systematically older than previously reported ages. These results suggest periods of aggradation in the Alaknanda and Dehradun Valleys mainly between similar to 25 and 35 ka. This most likely reflects decreased stream power during periods of weakened monsoon. In addition, in-situ cosmogenic beryllium-10 was used to infer bedrock surface exposure ages, which are interpreted as episodes of active fluvial erosion. Resulting exposure ages span from 3 to 6 ka, suggesting that strath terraces were exposed relatively recently, and incision was dominant through most of the Holocene. In combination, our results support precipitation-driven fluvial dynamics, which regulates the balance between stream power and sediment supply. On a larger spatial scale, however, fluvial dynamics are probably not spatially homogeneous as aggradation could have been taking place in adjacent catchments while incision dominated in the study area. (C) 2018 Elsevier Ltd. All rights reserved.
We experimentally demonstrate efficient switching of the hard x-ray Bragg reflectivity of a SrRuO3 /SrTiO3 superlattice by optical excitation of large-amplitude coherent acoustic superlattice phonons. The rocking curve changes drastically on a 1 ps timescale. The (0 0 116) reflection is almost extinguished (Delta R/R-0=-0.91), while the (0 0 118) reflection increases by more than an order of magnitude (Delta R/R-0=24.1). The change of the x-ray structure factor depends nonlinearly on the phonon amplitude, allowing manipulation of the x-ray response on a timescale considerably shorter than the phonon period. Numerical simulations for a superlattice with slightly changed geometry and realistic parameters predict a switching-contrast ratio Delta R/R-0 of 700 with high reflectivity.
Context. X-ray radiation from accreting compact objects is an important part of stellar feedback. The metal-poor galaxy ESO 338-4 has experienced vigorous starburst during the last <40 Myr and contains some of the most massive super star clusters in the nearby Universe. Given its starburst age and its star-formation rate, ESO 338-4 is one of the most efficient nearby manufactures of neutron stars and black holes, hence providing an excellent laboratory for feedback studies. Aims. We aim to use X-ray observations with the largest modern X-ray telescopes XMM-Newton and Chandra to unveil the most luminous accreting neutron stars and black holes in ESO 338-4. Methods. We compared X-ray images and spectra with integral field spectroscopic observations in the optical to constrain the nature of strong X-ray emitters. Results. X-ray observations uncover three ultraluminous X-ray sources (ULXs) in ESO 338-4. The brightest among them, ESO 338 X-1, has X-ray luminosity in excess of 10(40) erg s(-1). We speculate that ESO 338-4 X-1 is powered by accretion on an intermediate-mass (greater than or similar to 300 M-circle dot)black hole. We show that X-ray radiation from ULXs and hot superbubbles strongly contributes to He II ionization and general stellar feedback in this template starburst galaxy.