This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via CrossRef Citing Articles via Web of Science (26) Citing Articles via Google Scholar Google Scholar Articles by Galván, A. Articles by Fernández, E. Search for Related Content PubMed PubMed Citation Articles by Galván, A. Articles by Fernández, E. Agricola Articles by Galván, A. Articles by Fernández, E.

Metabolism and Enzymology

Nitrate Reductase Regulates Expression of Nitrite Uptake and Nitrite Reductase Activities in Chlamydomonas reinhardtii ¹

Departamento de Bioquímica y Biología Molecular y Fisiología, Facultad de Ciencias, Universidad de Córdoba, E-14071 Córdoba, Spain

In Chlamydomonas reinhardtii mutants defective at the structural locus for nitrate reductase (nit-1) or at loci for biosynthesis of the molybdopterin cofactor (nit-3, nit-4, or nit-5 and nit-6), both nitrite uptake and nitrite reductase activities were repressed in ammonium-grown cells and expressed at high amounts in nitrogen-free media or in media containing nitrate or nitrite. In contrast, wild-type cells required nitrate induction for expression of high levels of both activities. In mutants defective at the regulatory locus for nitrate reductase (nit-2), very low levels of nitrite uptake and nitrite reductase activities were expressed even in the presence of nitrate or nitrite. Both restoration of nitrate reductase activity in mutants defective at nit-1, nit-3, and nit-4 by isolating diploid strains among them and transformation of a structural mutant upon integration of the wild-type nit-1 gene gave rise to the wild-type expression pattern for nitrite uptake and nitrite reductase activities. Conversely, inactivation of nitrate reductase by tungstate treatment in nitrate, nitrite, or nitrogen-free media made wild-type cells respond like nitrate reductase-deficient mutants with respect to the expression of nitrite uptake and nitrite reductase activities. Our results indicate that nit-2 is a regulatory locus for both the nitrite uptake system and nitrite reductase, and that the nitrate reductase enzyme plays an important role in the regulation of the expression of both enzyme activities.

This article has been cited by other articles:

				D. Baurain, M. Dinant, N. Coosemans, and R. F. Matagne Regulation of the Alternative Oxidase Aox1 Gene in Chlamydomonas reinhardtii. Role of the Nitrogen Source on the Expression of a Reporter Gene under the Control of the Aox1 Promoter Plant Physiology, March 1, 2003; 131(3): 1418 - 1430. [Abstract] [Full Text] [PDF]

				J. Rexach, E. Fernández, and A. Galván The Chlamydomonas reinhardtii Nar1 Gene Encodes a Chloroplast Membrane Protein Involved in Nitrite Transport PLANT CELL, August 1, 2000; 12(8): 1441 - 1454. [Abstract] [Full Text]

				M. T. Navarro, E. Guerra, E. Fernandez, and A. Galvan Nitrite Reductase Mutants as an Approach to Understanding Nitrate Assimilation in Chlamydomonas reinhardtii Plant Physiology, January 1, 2000; 122(1): 283 - 290. [Abstract] [Full Text] [PDF]

				J. Rexach, B. Montero, E. Fernandez, and A. Galvan Differential Regulation of the High Affinity Nitrite Transport Systems III and IV in Chlamydomonas reinhardtii J. Biol. Chem., September 24, 1999; 274(39): 27801 - 27806. [Abstract] [Full Text] [PDF]

				A. Galván, A. Quesada, and E. Fernández Nitrate and Nitrite Are Transported by Different Specific Transport Systems and by a Bispecific Transporter in Chlamydomonas reinhardtii J. Biol. Chem., January 26, 1996; 271(4): 2088 - 2092. [Abstract] [Full Text] [PDF]