Three Nrt2 genes are differentially regulated in Chlamydomonas reinhardtii |
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| Authors: | A Quesada J Hidalgo and E Fernández |
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| Institution: | (1) Departamento de Biología Experimental, Facultad de Ciencias Experimentales, Universidad de Jaén, E-23071 Jaén, Spain Tel.: +34-53-21-25-23; Fax: +34-53-21-21-41 Email: almolina@ujaen.es, ES;(2) Departamento de Bioquímica y Biología Molecular e Instituto Andaluz de Biotecnología, Facultad de Ciencias, Universidad de Córdoba, E-14071, Córdoba, Spain, ES |
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| Abstract: | 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.
Received: 6 October 1997 / Accepted: 30 December 1997 |
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| Keywords: | Chlamydomonas reinhardtii mRNA expression Nitrate transport Nitrite transport Nrt2 |
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