Three Nrt2 genes are differentially regulated in Chlamydomonas reinhardtii.
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.
Quesada
A
A
Departamento de Biología Experimental, Facultad de Ciencias Experimentales, Universidad de Jaén, Spain. almolina@ujaen.es
Hidalgo
J
J
Fernández
E
E
D000818:Animals; D027321:Anion Transport Proteins; D001693:Biological Transport, Active; D002352:Carrier Proteins / Q000235:genetics* / Q000378:metabolism; D016825:Chlamydomonas reinhardtii / Q000235:genetics* / Q000378:metabolism; D015536:Down-Regulation; D015966:Gene Expression Regulation, Fungal; D000091285:Nitrate Transporters; D009566:Nitrates / Q000378:metabolism; D010940:Plant Proteins; D000644:Quaternary Ammonium Compounds / Q000378:metabolism; D015183:Restriction Mapping
D027321:Anion Transport Proteins; D002352:Carrier Proteins; D000091285:Nitrate Transporters; D009566:Nitrates; D010940:Plant Proteins; D000644:Quaternary Ammonium Compounds