Single-nucleotide polymorphisms contribute to phenotypic diversity in maize. Creation and functional annotation of point mutations has been limited by the low efficiency of conventional methods based on random mutatio...Single-nucleotide polymorphisms contribute to phenotypic diversity in maize. Creation and functional annotation of point mutations has been limited by the low efficiency of conventional methods based on random mutation. An efficient tool for generating targeted single-base mutations is desirable for both functional genomics and precise genetic improvement. The objective of this study was to test the efficiency of targeted C-to-T base editing of two non-allelic acetolactate synthase(ALS) in generating sulfonylurea herbicide-resistant mutants. A CRISPR/Cas9 nickase-cytidine deaminase fused with uracil DNA glycosylase inhibitor(UGI) was employed to achieve targeted conversion of cytosine to thymine in ZmALS1 and ZmALS2. Both protoplasts and recovered mutant plants showed the activity of the cytosine base editor, with an in vivo efficiency of up to 13.8%. Transgene-free edited plants harboring a homozygous ZmALS1 mutation or a ZmALS1 and ZmALS2 double mutation were tested for their resistance at a dose of up to 15-fold the recommended limit of chlorsulfuron, a sulfonylurea herbicide widely used in agriculture. Targeted base editing of C-to-T per se and a phenotype verified in the generated mutants demonstrates the power of base editing in precise maize breeding.展开更多
通过对超高压直流输电模型研究,发现低压限流控制器(voltage dependent current order limiter,VDCOL)的静态恢复关系和获取补偿电压的方法对连续换相失败有较大的影响,改变VDCOL所采用数学模型的斜率和获取补偿电压方法有利于减少连续...通过对超高压直流输电模型研究,发现低压限流控制器(voltage dependent current order limiter,VDCOL)的静态恢复关系和获取补偿电压的方法对连续换相失败有较大的影响,改变VDCOL所采用数学模型的斜率和获取补偿电压方法有利于减少连续换相失败次数。为降低直流输电系统发生连续换相失败的可能性,提出了基于虚拟电阻电流限制控制方法的精确变斜率低压限流控制器的设计方案。使用PSCAD中的CIGRE标准测试模型进行相关仿真,最后通过对相关数据的分析,验证了所提出的控制方法在单相和三相接地故障中对抑制连续换相失败的有效性。展开更多
基金supported by the Key Area Research and Development Program of Guangdong Province(2018B020202008)the National Natural Science Foundation of China(31771808)+2 种基金Beijing Municipal Science and Technology Project(D171100007717001)the National Key Research and Development Program of China(2016YFD0101803)National Engineering Laboratory for Crop Molecular Breeding。
文摘Single-nucleotide polymorphisms contribute to phenotypic diversity in maize. Creation and functional annotation of point mutations has been limited by the low efficiency of conventional methods based on random mutation. An efficient tool for generating targeted single-base mutations is desirable for both functional genomics and precise genetic improvement. The objective of this study was to test the efficiency of targeted C-to-T base editing of two non-allelic acetolactate synthase(ALS) in generating sulfonylurea herbicide-resistant mutants. A CRISPR/Cas9 nickase-cytidine deaminase fused with uracil DNA glycosylase inhibitor(UGI) was employed to achieve targeted conversion of cytosine to thymine in ZmALS1 and ZmALS2. Both protoplasts and recovered mutant plants showed the activity of the cytosine base editor, with an in vivo efficiency of up to 13.8%. Transgene-free edited plants harboring a homozygous ZmALS1 mutation or a ZmALS1 and ZmALS2 double mutation were tested for their resistance at a dose of up to 15-fold the recommended limit of chlorsulfuron, a sulfonylurea herbicide widely used in agriculture. Targeted base editing of C-to-T per se and a phenotype verified in the generated mutants demonstrates the power of base editing in precise maize breeding.
文摘通过对超高压直流输电模型研究,发现低压限流控制器(voltage dependent current order limiter,VDCOL)的静态恢复关系和获取补偿电压的方法对连续换相失败有较大的影响,改变VDCOL所采用数学模型的斜率和获取补偿电压方法有利于减少连续换相失败次数。为降低直流输电系统发生连续换相失败的可能性,提出了基于虚拟电阻电流限制控制方法的精确变斜率低压限流控制器的设计方案。使用PSCAD中的CIGRE标准测试模型进行相关仿真,最后通过对相关数据的分析,验证了所提出的控制方法在单相和三相接地故障中对抑制连续换相失败的有效性。
