甜菜nia基因的克隆及不同氮素形态诱导的差异表达

利用同源序列克隆方法从二倍体甜菜品种Ty7中获得氮素诱导nia基因片段，通过RACE技术克隆nia基因全长序列，该基因ORF长度2 718 bp，编码905个氨基酸，并已在GenBank上登录(EU163265)，基因组中nia以低拷贝数存在。nia编码蛋白的等电点为6.12，推测分子量为102 kD，以NADH为电子供体。为揭示不同氮素形态和处理对甜菜nia基因表达的影响，采用半定量PCR方法检测不同氮素形态诱导nia基因mRNA的表达，同时测定酶活力。结果表明，当铵态氮诱导nia基因时，低浓度的铵离子能促进基因的表达，过高浓度的铵离子抑制基因的表达。当硝态氮诱导nia基因时，随处理浓度的增加，nia的表达加强，呈正相关关系。用30 mmol L^–1硝态氮诱导4 h后，nia基因表达达最高值，约在6 h后，表达明显下降。

Cloning of nia Gene and Its Differential Expression Induced by Different Nitro-gen Forms in Sugar Beet (Beta vulgaris L.)

From diploid species Ty7, a cDNA clone related to nitrate reduction was isolated by Homology-based cloning. Accord-ing to its sequences information, a novel full-length cDNA termed nia (accession number: EU163265) was obtained by using rapid amplification of cDNA ends (RACE). nia was 3 247 bp long containing a 2 718 bp ORF, encoded 905 amino acids with a theoretical molecular weight of 102 kD and an isoelectric point of 6.12. Southern bloting proved that nia gene of Ty7 existed in the form of low copies. It...