Quesada A, Hidalgo J, Fernández E
Departamento de Biología Experimental, Facultad de Ciencias Experimentales, Universidad de Jaén, Spain.
Mol Gen Genet. 1998 May;258(4):373-7. doi: 10.1007/s004380050743.
Two new nitrate assimilation-related genes, Nrt2;3 and Nar5, have been identified in Chlamydomonas reinhardtii. The Nrt2;3 gene is a new member of the Nrt2 family, encoding high-affinity nitrate (nitrite) transporters. Like that of the nitrate assimilation genes, expression of the Nrt2;3 gene is down-regulated by ammonium and positively controlled by Nit2, a regulatory locus specific for the pathway. The three Nrt2 genes of C. reinhardtii are differentially regulated by the nitrogen source. Expression of Nrt2;3 and of Nrt2;1, a nitrate/nitrite-bispecific transporter gene, was induced by nitrate and more efficiently by nitrite. Accumulation of mRNA of Nrt2;2, the nitrate-specific transporter gene, was only induced efficiently by nitrate. The Nar5 gene is located upstream of the Nrt2;3 genomic region and expression of its mRNA is down-regulated by ammonium. The Nrt2;3 and Nar5 genes are overexpressed in a deletion mutant that lacks nitrate assimilation loci.
在莱茵衣藻中已鉴定出两个与硝酸盐同化相关的新基因，即Nrt2;3和Nar5。Nrt2;3基因是Nrt2家族的新成员，编码高亲和力硝酸盐（亚硝酸盐）转运蛋白。与硝酸盐同化基因一样，Nrt2;3基因的表达受铵抑制，并由该途径特有的调控位点Nit2正向调控。莱茵衣藻的三个Nrt2基因受氮源的差异调控。Nrt2;3和Nrt2;1（一种硝酸盐/亚硝酸盐双特异性转运蛋白基因）的表达由硝酸盐诱导，由亚硝酸盐诱导更有效。硝酸盐特异性转运蛋白基因Nrt2;2的mRNA积累仅由硝酸盐有效诱导。Nar5基因位于Nrt2;3基因组区域的上游，其mRNA的表达受铵抑制。Nrt2;3和Nar5基因在缺乏硝酸盐同化位点的缺失突变体中过表达。
