This group uses the photosynthetic eukaryotic alga Chlamydomonas reinhardtii as a model plant for studying fundamental questions of knowledge in these systems. Currently focuses its attention on the following aspects:

1.Nitrate/nitrite transport and reduction.

Proteins NRT2 were identified as responsible for high-affinity nitrate / nitrite transport at the plasma membrane level. Systems can act as single sytem or as two-component system, in combination with NAR2. NAR1 proteins mediate high affinity transport of nitrite into the chloroplast depending on the availability of carbon and may also mediate the transport of bicarbonate and other metabolites.

2. Molybdenum metabolism and apo-enzyme assembly.

Molybdenum is essential for building the active site of nitrate reduction, in the nitrate reductase enzyme, where it participates in the active form of molybdopterin cofactor (Moco). We have identified MOT1 as a transporter of high affinity molybdate, which is present in the various organisms with the exception of animals. We have also identified MOT2 present in eukaryotic organisms (like humans) but absent in prokaryotes. MCP1 is a Moco carrier protein involved in protecting Moco against degradation by oxygen, and its transfer to apo-molybdoenzyme. Recently, we identified the ARC system in plants that participates in reduction of hydroxy derivative of nitrogenous bases, which are toxic in various prokaryotes and eukaryotes. This is a molybdoenzyme allowing the detoxification of these compounds. The Chlamydomonas ARC system is similar to that of humans and involves cytochrome b5 and cytochrome b5 reductase.

3. Nitrate and ammonium signalling for the regulation of the pathway.
Nitrate is not only a vital source of nitrogen but also a positive signal for the expression of genes for nitrate assimilation and other cellular processes. By contrast, ammonia and its derivatives provide a negative signal. We have obtained a library of ordered insertional mutants to identify regulatory genes. The "sensing" of nitrate by the promoter of the nitrate reductase gene depends exclusively on intracellular nitrate concentrations determined by the activity of transporters. We have characterized as a transcription factor NIT2 from the leucine zipper type that mediates the signal of nitrate. The negative signaling is complex and depends on the activity of various genes including a nitric oxide-dependent guanylate cyclase. The negative effect of ammonium in turn depends on its balance with the positive signal of nitrate.

4.Starch and hydrogen photoproduction.

We are identifying mutant strains of Chlamydomonas that have an increased capacity to store starch and are capable of an efficient hydrogen photoproduction.

Chamizo-Ampudia A, Galván A, Fernández E, Llamas A (2011) The Chlamydomonas molybdenum cofactor enzyme crARC has a Zn-dependent activity and similar protein partners as its human homologue. Eukaryotic Cell (in press)

Gonzalez-Ballester D, Pootakham W, Mus F, Yang W, Catalanotti C, Magneschi L, Higuera JJ, de Montaigu A, Prior M, Galván A, Fernandez E, Grossman AR (2011) Reverse Genetics in Chlamydomonas: A Moderate Throughput Platform for Isolating Insertional Mutants. Plant methods 7:24

Llamas A, Tejada-Jiménez M, Fernández E, Galván A. (2011) Molybdenum metabolism in the alga Chlamydomonas stands at the crossroad of those in Arabidopsis and humans. Metallomics 3(6):578-90.

Tejada-Jiménez M, Galván A, Fernández E (2011) Algae and humans share a molybdate transporter. Proc Natl Acad Sci U S A. 108(16):6420-5.

Ermilova EV, Zalutskaya ZM, Nikitin MM, Lapina TV, Fernández E (2010) Regulation by light of ammonium transport systems in Chlamydomonas reinhardtii. Plant Cell Environ 33(6):1049-5

de Montaigu A, Sanz-Luque E, Galván A, Fernández E (2010) A soluble guanylate cyclase mediates negative signaling by ammonium on expression      of nitrate reductase in Chlamydomonas. Plant Cell. 22(5):1532-48.

Tejada-Jiménez M, Galván A, Fernández E, Llamas A (2009) Homeostasis of the micronutrients Ni, Mo and Cl with specific biochemical functions. Curr Opin Plant Biol 12(3):358-863

Castaings L, Camargo A, Pocholle D, Gaudon V, Texier Y, Boutet-Mercey S, Taconnat L, Renou JP, Daniel-Vedele F, Fernandez E, Meyer C, Krapp A. (2009) The nodule inception-like protein 7 modulates nitrate sensing and metabolism in Arabidopsis. Plant J.  57(3):426-435

Fernández E, Llamas A, Galvan A (2009) Nitrogen assimilation and its regulation in Chlamydomonas. In: The Chlamydomonas Sourcebook: Introduction to Chlamydomonas and Its Laboratory Use, 2nd Edition, Vol.2, pp69-114, Academic Press, New York
           
 Tejada-Jiménez M, Llamas A, Sanz-Luque E, Galván A,Fernández E  (2007) A high-affinity molybdate transporter in eukaryotes. Proc Natl Acad Sci U S A. 104(50):20126-20130.

Llamas A, Tejada-Jimenez M, Gonzalez-Ballester D, Higuera JJ, Schwarz G, Galvan A, Fernandez E (2007) Eukaryotic Cell 6 (6): 1063-1067 .