Development of highly glyphosate-tolerant tobacco by coexpression of glyphosate acetyltransferase gat and EPSPS G2-aroA genes

The widely used herbicide glyphosate targets 5-enolpyruvylshikimate-3-phosphate synthase(EPSPS).Glyphosate acetyltransferase(GAT)effectively detoxifies glyphosate by N-acetylation.With the aim of identifying a new strategy for development of glyphosate-tolerant crops,the plant expression vector pG2-GAT harboring gat and G2-aroA(encoding EPSPS)has been transformed into tobacco(Nicotiana tabacum)to develop novel plants with higher tolerance to glyphosate.Results from Southern and Western blotting analyses indicated that the target genes were integrated into tobacco chromosomes and expressed effectively at the protein level.Glyphosate tolerance was compared among transgenic tobacco plants containing gat,G2-aroA,or both genes.Plants containing both gat and G2-aroA genes were the most glyphosate-tolerant.This study has shown that a combination of different strategies may result in higher tolerance in transgenic crops,providing a new approach for development of glyphosate-tolerant crops.

Calibration of Mars Energetic Particle Analyzer (MEPA)

The first Mars exploration mission of China(Tianwen-1)is scheduled to be launched in 2020;a charged particle telescope,the Mars Energetic Particle Analyzer(MEPA),is carried as one of the payloads on the orbiter.The MEPA is designed to measure solar energetic particles(SEPs)and galactic cosmic rays(GCRs)in the near-Mars space and in the transfer orbit from Earth to Mars.Before the launch,the MEPA was calibrated in ground experiments with radioactive sources,electronic pulses,and accelerator beams.The calibration parameters,such as energy conversion constants,threshold values for the triggers,and particle identification criteria,were determined and have been stored for onboard use.The validity of the calibration parameters has been verified with radioactive sources and beams.The calibration results indicate that the MEPA can measure charged particles reliably,as designed,and that it can satisfy the requirements of the Tianwen-1 mission.

Effects of discharge parameters on the micro-hollow cathode sustained glow discharge

The effects of parameters such as pressure,first anode radius,and the cavity diameter on the micro-hollow cathode sustained glow discharge are investigated by using a two-dimensional self-consistent fluid model in pure argon.The results indicate that the three parameters influence the discharge in the regions inside and outside of the cavity.Under a fixed voltage on each electrode,a larger volume of high density plasma can be produced in the region between the first and the second anodes by selecting the appropriate pressure,the higher first anode,and the appropriate cavity diameter.As the pressure increases,the electron density inside the hollow cathode,the high density plasma volume between the first anode and second anodes,and the radial electric field in the cathode cavity initially increase and subsequently decrease.As the cavity diameter increases,the high-density plasma volume between the first and second anodes initially increases and subsequently decreases;whereas the electron density inside the hollow cathode decreases.As the first anode radius increases,the electron density increases both inside and outside of the cavity.Moreover,the increase of the electron density is more obvious in the microcathode sustained region than in the micro cavity region.The results reveal that the discharge inside the cavity interacts with that outside the cavity.The strong hollow cathode effect and the high-density plasma inside the cavity favor the formation of a sustained discharge between the first anode and the second anodes.Results also show that the radial boundary conditions exert a considerably weaker influence on the discharge except for a little change in the region close to the radial boundary.