Nitrate Assimilation in<i>Chlamydomonas</i>

Fernández, Emilio; Galván, Aurora

doi:10.1128/ec.00431-07

Cited by 117 publications

(95 citation statements)

References 73 publications

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“…Nitrate and nitrite are taken up via transporters encoded by members of the NRT1, NRT2, and NAR1 families (Quesada et al, 1993;Fernandez and Galvan, 2007). Nitrate assimilation requires energy for reduction to the level of ammonium by enzymes, nitrate reductase in the cytosol, and nitrite reductase in the chloroplast, both encoded by single genes in C. reinhardtii, NIA1/ NIT1 and NII1, respectively (Romero et al, 1987;Fernández et al, 1989;Quesada et al, 1998;Fernandez and Galvan, 2008;Hirasawa et al, 2010). Many of the genes involved in nitrate/nitrite uptake and assimilation are under the control of a positive regulator, the NIT2 transcription factor (Fernández and Matagne, 1986;Camargo et al, 2007).…”

Section: Introductionmentioning

confidence: 99%

Nitrogen-Sparing Mechanisms in Chlamydomonas Affect the Transcriptome, the Proteome, and Photosynthetic Metabolism

et al. 2014

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ORCID IDs: 0000-0002-7487-8014 (S.S.); 0000-0002-2594-509X (S.S.M.)Nitrogen (N) is a key nutrient that limits global primary productivity; hence, N-use efficiency is of compelling interest in agriculture and aquaculture. We used Chlamydomonas reinhardtii as a reference organism for a multicomponent analysis of the N starvation response. In the presence of acetate, respiratory metabolism is prioritized over photosynthesis; consequently, the N-sparing response targets proteins, pigments, and RNAs involved in photosynthesis and chloroplast function over those involved in respiration. Transcripts and proteins of the Calvin-Benson cycle are reduced in N-deficient cells, resulting in the accumulation of cycle metabolic intermediates. Both cytosolic and chloroplast ribosomes are reduced, but via different mechanisms, reflected by rapid changes in abundance of RNAs encoding chloroplast ribosomal proteins but not cytosolic ones. RNAs encoding transporters and enzymes for metabolizing alternative N sources increase in abundance, as is appropriate for the soil environmental niche of C. reinhardtii. Comparison of the N-replete versus N-deplete proteome indicated that abundant proteins with a high N content are reduced in N-starved cells, while the proteins that are increased have lower than average N contents. This sparing mechanism contributes to a lower cellular N/C ratio and suggests an approach for engineering increased N-use efficiency.

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Section: Introductionmentioning

confidence: 99%

Nitrogen-Sparing Mechanisms in Chlamydomonas Affect the Transcriptome, the Proteome, and Photosynthetic Metabolism

et al. 2014

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“…Although an increasing number of factors involved in nitrate signalling and response has been identified, the key factor in the mechanism for nitrate response, namely the transcription factor that primarily responds to nitrate signalling, has not yet been identified. Nitrate-responsive transcription factors have been identified in bacteria, fungi and algae [25][26][27] . However, no protein in higher plants is similar to the nitrateresponsive transcription factors in these organisms, suggesting that different factors might mediate nitrate signalling in higher plants.…”

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confidence: 99%

Arabidopsis NIN-like transcription factors have a central role in nitrate signalling

2013

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In plants, nitrate is not only a major nitrogen source but also a signalling molecule that modulates the expression of a wide range of genes and that regulates growth and development. The critical role of nitrate as a signalling molecule has been established for several decades. However, the molecular mechanisms underlying the nitrate response have remained elusive, as the transcription factor that primarily responds to nitrate signals has not yet been identified. Here we show that Arabidopsis NIN-LIKE PROTEIN (NLP) family proteins bind the nitrate-responsive cis-element and activate nitrate-responsive cis-element-dependent and nitrate-responsive transcription. Our results also suggest that the activity of NLPs is posttranslationally modulated by nitrate signalling. Furthermore, the suppression of NLP function impairs the nitrate-inducible expression of a number of genes and causes severe growth inhibition. These results indicate that NLPs are the transcription factors mediating the nitrate signal and thereby function as master regulators of the nitrate response.

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“…As shown in Figure 6, the ynt mutant does not show nitrite transport activity, but the complementation with CrNRT2.4 restores this activity, though it was less efficient than in the Hansenula wild type. In Chlamydomonas, NRT2.1/NAR2 is the most efficient high affinity transporter and bispecific for nitrate and nitrite [6,7]. Thus, data from Figure 5 suggest that NRT2.4 participates in nitrite transport, but its activity is masked by NRT2.1/NAR2.…”

Section: Nrt24 Is a Nitrite Transportermentioning

confidence: 83%

“…It is worth noting that to detect nitrite transport activity from the D2 strains and under the assayed conditions, high CO 2 , nitrate pre-incubation is required to induce nitrite transport [38]. In Chlamydomonas, NRT2.1/NAR2 is the most efficient high affinity transporter and bispecific for nitrate and nitrite [6,7]. Thus, data from Figure 5 suggest that NRT2.4 participates in nitrite transport, but its activity is masked by NRT2.1/NAR2.…”

Section: Nrt24 Is a Nitrite Transportermentioning

confidence: 99%

“…The main characteristics of the Chlamydomonas NRT2.1, NRT2.2, and NRT2.3 expression are its up-regulation by nitrate, and that they are under the control of NIT2, the master gene for nitrate assimilation in the alga [7,38]. The expression of NRT2.4 and NRT2.5 genes has been analyzed under different conditions: high versus low CO 2 , ammonium versus nitrate, and light versus darkness (Figure 4).…”

Section: Expression Of Nrt24 and Nrt25 Is Not Regulated By Nitrogenmentioning

confidence: 99%

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NRT2.4 and NRT2.5 Are Two Half-Size Transporters from the Chlamydomonas NRT2 Family

et al. 2016

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Abstract:The NRT2 transporters mediate High Affinity Nitrate/NitriteTransport (HAN/NiT), which are essential for nitrogen acquisition from these inorganic forms. The NRT2 proteins are encoded by a multigene family in plants, and contain 12 transmembrane-spanning domains. Chlamydomonas reinhardtii has six NRT2, two of which (NRT2.5 and NRT2.4) are located in Chromosome III, in tandem head to tail. cDNAs for these genes were isolated and their sequence revealed that they correspond to half-size NRT2 transporters each containing six transmembrane domains. NRT2.5 has long N-and C-termini sequences without known homology. NRT2.4 also contains long termini sequences but smaller than NRT2.5. Expression of both studied genes occurred at a very low level, slightly in darkness, and was not modified by the N or C source. Silencing of NRT2.4 by specific artificial miRNA resulted in the inhibition of nitrite transport in the absence of other HANNiT (NRT2.1/NAR2) in the cell genetic background. Nitrite transport activity in the Hansenula polymorpha ∆ynt::URA3 Leu2 mutant was restored by expressing CrNRT2.4. These results indicate that half-size NRT2 transporters are present in photosynthetic organisms and that NRT2.4 is a HANiT.

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Nitrate Assimilation inChlamydomonas

Cited by 117 publications

References 73 publications

Nitrogen-Sparing Mechanisms in Chlamydomonas Affect the Transcriptome, the Proteome, and Photosynthetic Metabolism

Nitrogen-Sparing Mechanisms in Chlamydomonas Affect the Transcriptome, the Proteome, and Photosynthetic Metabolism

Arabidopsis NIN-like transcription factors have a central role in nitrate signalling

NRT2.4 and NRT2.5 Are Two Half-Size Transporters from the Chlamydomonas NRT2 Family

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