A novel Gateway®-compatible binary vector allows direct selection of recombinant clones in Agrobacterium tumefaciens

<p>Abstract</p> <p>Background</p> <p>Cloning genes into plasmid vectors is one of the key steps for studying gene function. Recently, Invitrogen™ developed a convenient Gateway^®cloning system based on the site-specific DNA recombination properties of bacteriophage lambda and the cytotoxic protein ccdB, which is lethal to most <it>E. coli </it>strains. The ccdB protein, however, is not toxic to <it>Agrobacterium tumefaciens</it>, an important player often used for studying gene function <it>in planta</it>. This limits the direct application of the Gateway^®cloning system in plant transformation-mediated research.</p> <p>Results</p> <p>In this study, we constructed a novel Gateway^®-compatible destination vector, pEG101-SacB/R, by replacing the <it>ccdB </it>gene with a <it>SacB-SacR </it>gene cassette as the negative selectable marker.</p> <p>Conclusion</p> <p>Our results demonstrate that the new pEG101-SacB/R destination vector can be used for Gateway^®cloning in <it>Agrobacterium tumefaciens</it>. pEG101-SacB/R will be a valuable tool for high-throughput functional analysis of genes <it>in planta</it>.</p

Stress and its effect on optical properties of GaN epilayers grown on Si(111), 6H-SiC(0001), and c-plane sapphire

Stress and its effects on optical properties of GaN epilayers grown in Si(111), 6H-SiC(0001), and c-plane sapphire were investigated. Large tensile stress was present in GaN epilayers grown on Si and 6H-SiC, and a small compressive stress appeared in the film grown on sapphire. The results showed that the thermal mismatch between the epilayers and the substrates plays a major role in determining the residual strain in the films.published_or_final_versio

Repression of phosphoinositide-dependent protein kinase 1 expression by ciglitazone via Egr-1 represents a new approach for inhibition of lung cancer cell growth.

published_or_final_versio

Measured and calculated seismic velocities and densities for granulites from xenolith occurrences and adjacent exposed lower crustal sections: A comparative study from the North China craton

Granulites from the Neogene xenolith-bearing Hannuoba alkaline basalt and from the Manjinggou-Wayaokou exposed lower crustal section in the Archean Huai'an terrain, which occurs within and surrounds the Hannuoba basalt, provide a unique opportunity for a comparative study on petrophysical properties and composition of the lower crust represented by these two types of samples. P and S wave velocities and densities of 12 Hannuoba lower crustal xenoliths and one associated spinel lherzolite xenolith as well as nine granulites and granulite-facies metasedimentary rocks from the Archean Huai'an terrain were measured in laboratory at pressures up to 600 MPa and temperatures up to 600°C. Calculations of P and S wave velocities were also made for the same suite of samples based on modal mineralogy and single-crystal velocities whose variations with composition are considered by using microprobe analyses and velocities of end members. The measured and calculated Vp at room temperature and 600 MPa, where the microcrack effect is considered to be almost eliminated, agree within 4% for rocks from the Manjinggou-Wayaokou section and the adjacent Wutai-Jining upper crustal to upper lower crustal section. In contrast, the xenoliths show systematically lower measured Vp by up to 15% relative to calculated velocities, even if decompression-induced products of kelyphite and glass are taken into account. The lower measured velocities for xenoliths are attributed to grain boundary alteration and residual porosity. This implies that although granulite xenoliths provide direct information about lower crustal constitution and chemical composition, they are not faithful samples for studying in situ seismic properties of the lower crust in terms of measured velocities due to alterations during their entrainment to the surface, which changes their physical properties significantly. In this respect, granulites from high-grade terrains are better samples because they are not subjected to significant changes during their slow transport to the surface and because physical properties depend primarily on mineralogy in addition to pressure and temperature. On the other hand, calculated velocities for granulite xenoliths are consistent with velocities for granulites from terrains, suggesting that they can be also used to infer lower crust composition by correlating with results from seismic refraction studies. Copyright 2000 by the American Geophysical Union.published_or_final_versio

High-energy scale revival and giant kink in the dispersion of a cuprate superconductor

In the present photoemission study of a cuprate superconductor Bi1.74Pb0.38Sr1.88CuO6+delta, we discovered a large scale dispersion of the lowest band, which unexpectedly follows the band structure calculation very well. The incoherent nature of the spectra suggests that the hopping-dominated dispersion occurs possibly with the assistance of local spin correlations. A giant kink in the dispersion is observed, and the complete self-energy containing all interaction information is extracted for a doped cuprate in the low energy region. These results recovered significant missing pieces in our current understanding of the electronic structure of cuprates.Comment: 4 pages, 3 figures, submitted to Phys. Rev. Lett. on May 21, 200

Chemical characterization of PM2.5 from a southern coastal city of China:applications of modeling and chemical tracers in demonstrationof regional transport

An intensive sampling campaign of airborne fine particles (PM2.5) was conducted at Sanya, a coastal city in Southern China, from January to February 2012. Chemical analyses and mass reconstruction were used identify potential pollution sources and investigate atmospheric reaction mechanisms. A thermodynamic model indicated that low ammonia and high relative humidity caused the aerosols be acidic and that drove heterogeneous reactions which led to the formation of secondary inorganic aerosol. Relationships among neutralization ratios, free acidity, and air-mass trajectories suggest that the atmosphere at Sanya was impacted by both local and regional emissions. Three major transport pathways were identified, and flow from the northeast (from South China) typically brought the most polluted air to Sanya. A case study confirmed strong impact from South China (e.g., Pearl River Delta region) (contributed 76.8% to EC, and then this result can be extended to primary pollutants) when the northeast winds were dominant. The Weather Research Forecasting Black carbon model and trace organic markers were used to apportion local pollution versus regional contributions. Results of the study offer new insights into the atmospheric conditions and air pollution at this coastal city

SacB-SacR Gene Cassette As the Negative Selection Marker to Suppress Agrobacterium Overgrowth in Agrobacterium-Mediated Plant Transformation

Agrobacterium overgrowth is a common problem in Agrobacterium-mediated plant transfor-mation. To suppress the Agrobacterium overgrowth, various antibiotics have been used during plant tissue culture steps. The antibiotics are expensive and may adversely affect plant cell differentiation and reduce plant transformation efficiency. The SacB-SacR proteins are toxic to most Agrobacterium tumefaciens strains when they are grown on culture medium sup¬plemented with sucrose. Therefore, SacB-SacR genes can be used as negative selection markers to suppress the overgrowth of Agrobacterium tumefaciens in the plant tissue culture process. We generated a mutant Agrobacterium tumefaciens strain GV2260 (recA-SacB/R) that has the SacB-SacR cassette inserted into the bacterial genome at the recA gene locus. The mutant Agrobacterium strain is sensitive to sucrose but maintains its ability to transform plant cells in both transient and stable transformation assays. We demonstrated that the mutant strain GV2260 (recA-SacB/R) can be inhibited by sucrose that reduces the overgrowth of Agrobacterium and therefore improves the plant transformation efficiency. We employed GV2260 (recA-SacB/R) to generate stable transgenic N. benthamiana plants expressing a CRISPR-Cas9 for knocking out a WRKY transcrip¬tion factor