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The use of mutants to study nitrate assimilation in green microalgae
A. Galván, Quesada, A. and Fernández, E.

In Chlamydomonas reinhardtii, seven genes were genetically identified for the nitrate assimilation pathway. They are scattered in the algal genome: nit1 ncodes the NR apoprotein, nit2 a positive-acting regulatory product, and five more genes are related to the molybdopterin cofactor biosynthesis. Nit1 is clustered together with four additional genes related to nitrate assimilation (nar), which corregulate with nit1. Mutants which have some of the nitrate assimilation clustered genes and which lack some of them were obtained and characterized. Nitrate transport seems to be mediated in C. reinhardtii by two systems each containing the NAR2 product and either NAR3 or NAR4 which are highly hydrophobic proteins. A different system appears to account for nitrite transport. Expression of nitl was dependent on the presence of nitrate and light in cells growing in mineral minimum medium. However, the requirement for light was removed in cells capable of utilizing acetate.

Keywords: nitrate reductase, nitrate transporter, gene cluster. ABBREVIATIONS: NR = nitrate reductase; NT = nitrate transporter; NiR = nitrite reductase; NiT = nitrite transporter.
Contents of this volume Sci. Mar. 60(Suppl.1) : 191-194 Back PDF
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