To generate transgenic plants capable of utilizing exogenous phytate, an Aspersgillus fumigatus phytase gene （fphyA） was constitutively expressed in tobacco and recombinant enzyme was secreted from plant roots into ...To generate transgenic plants capable of utilizing exogenous phytate, an Aspersgillus fumigatus phytase gene （fphyA） was constitutively expressed in tobacco and recombinant enzyme was secreted from plant roots into the rhizosphere using the signal sequence from tobacco calreticulin. After 40 days of plant growth in hydroponic media, phytase activities in leaves, stems, roots and growth media of transgenic plants were 8.6-fold, 7.4-fold, 12.6-fold and 14.3-fold higher than those of wild-type plants. Signifi- cant improvements in plant growth and phosphorus （P） utilization were observed in the transgenic plants. When phytate was supplied as the sole P source, 45-day-old transgenic tobaccos accumulated 1.0-fold and 0.5-fold more shoot and root biomass than wild-type tobaccos, with a concomitant of l. 7-fold increase in total P concentration. These results indicate that secretive expression of the A. fumigatus phytase improves acquisition and use of P from phytate in plants.展开更多
Highly reliable and bendable dielectrics are desired in flexible or bendable electronic devices for future applications. Hexagonal boron nitride （h-BN） can be used as bendable dielectric due to its wide band gap. He...Highly reliable and bendable dielectrics are desired in flexible or bendable electronic devices for future applications. Hexagonal boron nitride （h-BN） can be used as bendable dielectric due to its wide band gap. Here, we fabricate high quality h-BN films with controllable thickness by a low pressure chemical vapor deposition method. We demonstrate a parallel-plate capacitor using h-BN film as the dielectric. The h-BN capacitors are reliable with a high breakdown field strength of -9.0 MV/cm. Tunneling current across the h-BN film is inversely exponential to the thickness of dielectric, which makes the capacitance drop significantly. The h-BN capacitor shows a best specific capacitance of 6.8 F/cm^2, which is one order of magnitude higher than the calculated value.展开更多
文摘To generate transgenic plants capable of utilizing exogenous phytate, an Aspersgillus fumigatus phytase gene （fphyA） was constitutively expressed in tobacco and recombinant enzyme was secreted from plant roots into the rhizosphere using the signal sequence from tobacco calreticulin. After 40 days of plant growth in hydroponic media, phytase activities in leaves, stems, roots and growth media of transgenic plants were 8.6-fold, 7.4-fold, 12.6-fold and 14.3-fold higher than those of wild-type plants. Signifi- cant improvements in plant growth and phosphorus （P） utilization were observed in the transgenic plants. When phytate was supplied as the sole P source, 45-day-old transgenic tobaccos accumulated 1.0-fold and 0.5-fold more shoot and root biomass than wild-type tobaccos, with a concomitant of l. 7-fold increase in total P concentration. These results indicate that secretive expression of the A. fumigatus phytase improves acquisition and use of P from phytate in plants.
基金This work was supported by the National Natural Science Foundation of China （No. 51172122）, the Foundation for the Author of National Excellent Doctoral Dissertation （No. 2007B37） and the Program for New Century Excellent Talents in University, the Tsinghua University Initiative Scientific Research Pro-gram （No. 20111080939）, and the China Postdoctoral Science Foundation （No. 2011M500310）. We thank Prof. Yonggang Zhao and Dr. Xingli Jiang for their help in testing the capacitors.
文摘Highly reliable and bendable dielectrics are desired in flexible or bendable electronic devices for future applications. Hexagonal boron nitride （h-BN） can be used as bendable dielectric due to its wide band gap. Here, we fabricate high quality h-BN films with controllable thickness by a low pressure chemical vapor deposition method. We demonstrate a parallel-plate capacitor using h-BN film as the dielectric. The h-BN capacitors are reliable with a high breakdown field strength of -9.0 MV/cm. Tunneling current across the h-BN film is inversely exponential to the thickness of dielectric, which makes the capacitance drop significantly. The h-BN capacitor shows a best specific capacitance of 6.8 F/cm^2, which is one order of magnitude higher than the calculated value.
