The <i>Chlamydomonas reinhardtii Nar1</i> Gene Encodes a Chloroplast Membrane Protein Involved in Nitrite Transport

Rexach, Jesús; Fernández, Emilio; Galván, Aurora

doi:10.1105/tpc.12.8.1441

Cited by 78 publications

(44 citation statements)

References 59 publications

(56 reference statements)

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“…These results also suggest that Ssu2 presents greater affinity for nitrate than Nar1. Indeed, Nar1 belongs to the FNT family, whose members are involved in nitrite transport and efflux (11,(21)(22)(23)25). Consistent with this, in the yni1⌬ nar1⌬ strain, nitrite is quickly accumulated (data not shown), while nitrate is slowly accumulated in the ynr1⌬ nar1⌬ strain, suggesting again that Nar1 presents a higher affinity for nitrite than for nitrate ( Fig.…”

Section: Discussionsupporting

confidence: 67%

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Molecular Components of Nitrate and Nitrite Efflux in Yeast

et al. 2014

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Some eukaryotes, such as plant and fungi, are capable of utilizing nitrate as the sole nitrogen source. Once transported into the cell, nitrate is reduced to ammonium by the consecutive action of nitrate and nitrite reductase. How nitrate assimilation is balanced with nitrate and nitrite efflux is unknown, as are the proteins involved. The nitrate assimilatory yeast Hansenula polymorpha was used as a model to dissect these efflux systems. We identified the sulfite transporters Ssu1 and Ssu2 as effective nitrate exporters, Ssu2 being quantitatively more important, and we characterize the Nar1 protein as a nitrate/nitrite exporter. The use of strains lacking either SSU2 or NAR1 along with the nitrate reductase gene YNR1 showed that nitrate reductase activity is not required for net nitrate uptake. Growth test experiments indicated that Ssu2 and Nar1 exporters allow yeast to cope with nitrite toxicity. We also have shown that the well-known Saccharomyces cerevisiae sulfite efflux permease Ssu1 is also able to excrete nitrite and nitrate. These results characterize for the first time essential components of the nitrate/nitrite efflux system and their impact on net nitrate uptake and its regulation.

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Section: Discussionsupporting

confidence: 67%

“…The structure of FocA strongly suggests that it is a channel rather than a transporter (23). In Chlamydomonas reinhardtii, some of the NAR1 genes are clearly regulated by carbon or nitrogen (24) and involved in nitrite transport in the chloroplast (25).…”

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confidence: 99%

Molecular Components of Nitrate and Nitrite Efflux in Yeast

et al. 2014

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“…In Chlamydomonas, the Nar1 gene, clustered with other nitrate assimilation genes ( fig. 1), encodes an integral protein of the chloroplast membranes, as deduced from the sequence of its putative transit peptide and immunodetection of NAR1 in the chloroplast envelope membranes with specific antibodies [74]. NAR1 sequence analysis predicts a protein with six transmembrane-spanning segments and significant homology to putative nitrite transport proteins from bacteria [75].…”

Section: Multi-author Review Articlementioning

confidence: 99%

“…NAR1 is also required for optimal cell growth under conditions of limiting nitrate. In addition to NAR1, other plastidic nitrite transporters seem to operate in Chlamydomonas [74]. Similarly to plasma membrane nitrate/nitrite transport, the picture of nitrite transport to the chloroplast also appears to be complex.…”

Section: Multi-author Review Articlementioning

confidence: 99%

Eukaryotic nitrate and nitrite transporters

Galván¹,

Fernández²

2001

CMLS, Cell. Mol. Life Sci.

126

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Nitrate transport is the key step controlling the amount of nitrate incorporated by the cells and subsequent of storage, reduction or export. Molecular, genetic and biochemical approaches to the study of eukaryotic nitrate/nitrite transporters allow an initial understanding of this step, which is much more complex and structured than previously suspected. At the plasma membrane level, two gene families, Nrt1 and Nrt2, account for high- and low-affinity nitrate transporters. Functionality of NRT1 from Arabidopsis and NRT2 proteins from Aspergillus and Chlamydomonas has been demonstrated. However, redundancy of these systems makes it difficult to assign particular physiological roles to each. Data on genes involved in the regulation of nitrate transport and reduction are still scarce. Information on nitrite transporters to the chloroplast is biased by the belief that in vivo nitrous acid diffuses freely to this organellum. The recent progress on these aspects is discussed in this review.

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“…The NAR2 protein is required for functional activity of either system I or II Zhou et al 2000) although its role in regulating nitrate transport is unknown. Finally, NAR1 represents a member from another family for the nitrite transport to the chloroplast that is required for nitrate assimilation at limiting nitrate or CO 2 concentrations in Chlamydomonas (Rexach et al 2000).…”

Section: Introductionmentioning

confidence: 99%

The activity of the high-affinity nitrate transport system I (NRT2;1, NAR2) is responsible for the efficient signalling of nitrate assimilation genes in Chlamydomonas reinhardtii

Rexach

Llamas

Fernández

et al. 2002

Planta

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The expression of nitrite uptake activity and the induction of transcripts from several nitrate assimilation genes (Nii1, Nrt2;1, Nrt2;3, and Nar1) have been analysed in Chlamydomonas reinhardtii Dang. strains bearing several sets of genes encoding nitrate transport systems. Different nitrate concentrations resulted in a differential induction pattern of nitrite uptake activity depending on which particular nitrate transport system was present in the cells, and that was directly related to their relative efficiency for nitrate transport. The presence of the high-affinity nitrate transport system I (NRT2;1, NAR2) made cells able to sense the very low concentrations of nitrate present in culture medium with no added nitrate and to express optimally Nii1, Nrt2;1, Nrt2;3, and Nar1 genes involved in nitrate/nitrite assimilation. In addition, strains lacking nitrate reductase activity overexpressed these gene transcripts as a result of continuous signalling by nitrate, but only those bearing an active system I. This study supports the hypothesis that signalling of nitrate assimilation genes occurs intracellularly in a process dependent on the nitrate uptake activity. The bispecific nitrate/nitrite transport system I with the highest affinity for nitrate is the most efficient one for signalling the expression of nitrate/nitrite assimilation genes in C. reinhardtii.

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The Chlamydomonas reinhardtii Nar1 Gene Encodes a Chloroplast Membrane Protein Involved in Nitrite Transport

Cited by 78 publications

References 59 publications

Molecular Components of Nitrate and Nitrite Efflux in Yeast

Molecular Components of Nitrate and Nitrite Efflux in Yeast

Eukaryotic nitrate and nitrite transporters

The activity of the high-affinity nitrate transport system I (NRT2;1, NAR2) is responsible for the efficient signalling of nitrate assimilation genes in Chlamydomonas reinhardtii

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