A distributed feedback （DFB） fiber laser with a ratio of the backward to forward output power of 1：100 was composed by a 45-ram-length asymmetrical phase-shifted fiber grating fabricated on the 50-mm erbium-doped p...A distributed feedback （DFB） fiber laser with a ratio of the backward to forward output power of 1：100 was composed by a 45-ram-length asymmetrical phase-shifted fiber grating fabricated on the 50-mm erbium-doped photosensitive fiber. Forward output laser was amplified using a certain length of Nufern EDFL-980-Hp erbium-doped fiber to absorb the surplus pump power after the active phase-shifted fiber grating and get population inversion. By using OptiSystem software, the best fiber length of the EDFL to get the highest gain was simulated. In order to keep the amplified laser with the narrow line-width and low noise, a narrow-band light filter consisting of a fiber Bragg grating （FBG） with the same Bragg wavelength as the laser and an optical circulator was used to filter the amplified spontaneous emission （ASE） noise of the out-cavity erbium-doped fiber. The designed laser structure sufficiently utilized the pump power, and a DFB fiber laser with the 32.5-mW output power, l l.5-kHz line width, and -87-dB/Hz relative intensity noise （R1N） at 300 mW of 980 nm pump power was brought out.展开更多
Synthetic gene activators consisting of nucleasedead Cas9(dCas9)for single-guide RNA(sgRNA)-directed promoter binding and a transcriptional activation domain(TAD)represent new tools for gene activation from endogenous...Synthetic gene activators consisting of nucleasedead Cas9(dCas9)for single-guide RNA(sgRNA)-directed promoter binding and a transcriptional activation domain(TAD)represent new tools for gene activation from endogenous genomic locus in basic and applied plant research.However,multiplex gene coactivation by d Cas9-TADs has not been demonstrated in whole plants.There is also room to optimize the performance of these tools.Here,we report that our previously developed gene activator,dCas9-TV,could simultaneously upregulate OsGW7 and OsER1 in rice by up to 3,738 fold,with one sg RNA targeting to each promoter.The gene coactivation could persist to at least the fourth generation.Astonishingly,thepolycistronictRNA-sgRNAexpression under the maize ubiquitin promoter,a Pol II promoter,could cause enormous activation of these genes by up to>40,000-fold in rice.Moreover,the yeast GCN4 coiled coil-mediated dCas9-TV dimerization appeared to be promising for enhancing gene activation.Finally,we successfully introduced a self-amplification loop for dCas9-TV expression in Arabidopsis to promote the transcriptional upregulation of AtFLS2,a previously characterized dCas9-TV-refractory gene with considerable basal expression.Collectively,this work illustrates the robustness of dCas9-TV in multigene coactivation and provides broadly useful strategies for boosting transcriptional activation efficacy of dCas9-TADs in plants.展开更多
文摘A distributed feedback （DFB） fiber laser with a ratio of the backward to forward output power of 1：100 was composed by a 45-ram-length asymmetrical phase-shifted fiber grating fabricated on the 50-mm erbium-doped photosensitive fiber. Forward output laser was amplified using a certain length of Nufern EDFL-980-Hp erbium-doped fiber to absorb the surplus pump power after the active phase-shifted fiber grating and get population inversion. By using OptiSystem software, the best fiber length of the EDFL to get the highest gain was simulated. In order to keep the amplified laser with the narrow line-width and low noise, a narrow-band light filter consisting of a fiber Bragg grating （FBG） with the same Bragg wavelength as the laser and an optical circulator was used to filter the amplified spontaneous emission （ASE） noise of the out-cavity erbium-doped fiber. The designed laser structure sufficiently utilized the pump power, and a DFB fiber laser with the 32.5-mW output power, l l.5-kHz line width, and -87-dB/Hz relative intensity noise （R1N） at 300 mW of 980 nm pump power was brought out.
基金supported by a grant from the National Transgenic Science and Technology Major Program of China(2019ZX08010003-001-009)。
文摘Synthetic gene activators consisting of nucleasedead Cas9(dCas9)for single-guide RNA(sgRNA)-directed promoter binding and a transcriptional activation domain(TAD)represent new tools for gene activation from endogenous genomic locus in basic and applied plant research.However,multiplex gene coactivation by d Cas9-TADs has not been demonstrated in whole plants.There is also room to optimize the performance of these tools.Here,we report that our previously developed gene activator,dCas9-TV,could simultaneously upregulate OsGW7 and OsER1 in rice by up to 3,738 fold,with one sg RNA targeting to each promoter.The gene coactivation could persist to at least the fourth generation.Astonishingly,thepolycistronictRNA-sgRNAexpression under the maize ubiquitin promoter,a Pol II promoter,could cause enormous activation of these genes by up to>40,000-fold in rice.Moreover,the yeast GCN4 coiled coil-mediated dCas9-TV dimerization appeared to be promising for enhancing gene activation.Finally,we successfully introduced a self-amplification loop for dCas9-TV expression in Arabidopsis to promote the transcriptional upregulation of AtFLS2,a previously characterized dCas9-TV-refractory gene with considerable basal expression.Collectively,this work illustrates the robustness of dCas9-TV in multigene coactivation and provides broadly useful strategies for boosting transcriptional activation efficacy of dCas9-TADs in plants.
