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Artículos publicados desde el 2008 incluído y disponibles al menos online.
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Cell and Molecular Life Science
Padilla S, Tran UC, Jiménez-Hidalgo M, López-Martín JM, Martín-Montalvo A, Clarke CF, Navas P, Santos-Ocaña C.

Coenzyme Q is a lipid molecule required for respiration and antioxidant protection. Q biosynthesis in Saccharomyces cerevisiae requires nine proteins (Coq1p-Coq9p). We demonstrate in this study that Q levels are modulated during growth by its conversion from demethoxy-Q (DMQ), a late intermediate. Similar conversion was produced when cells were subjected to oxidative stress conditions. Changes in Q6/DMQ6 ratio were accompanied by changes in COQ7 gene mRNA levels encoding the protein responsible for the DMQ hydroxylation, the penultimate step in Q biosynthesis pathway. Yeast coq null mutant failed to accumulate any Q late biosynthetic intermediate. However, in coq7 mutants the addition of exogenous Q produces the DMQ synthesis. Similar effect was produced by over-expressing ABC1/COQ8. These results support the existence of a biosynthetic complex that allows the DMQ6 accumulation and suggest that Coq7p is a control point for the Q biosynthesis regulation in yeast.

Nature Neuroscience
Antonio Rodríguez-Moreno & Ole Paulsen

NMDA receptors are necessary for both synaptic potentiation and depression, but the precise location of these receptors has not been established. By loading MK-801 into pre- or postsynaptic neurons during paired recordings of synaptically connected layer 4 and layer 2/3 neurons in mouse barrel cortex, we found that synaptic potentiation requires postsynaptic, but not presynaptic, NMDA receptors, whereas synaptic depression requires presynaptic, but not postsynaptic, NMDA receptors.

Environmental and Experimental Botany
Juan J. Camacho-Cristóbal, María Begoña Herrera-Rodríguez, Víctor M. Beato, Jesús Rexach, María T. Navarro-Gochicoa, José M. Maldonado and Agustín González-Fontes

Plant cell wall is a dynamic structure that is of fundamental importance in plant growth and development, as well as in the response to environmental stresses. There is direct evidence for a role of boron (B) in cross-linking of cell wall rhamnogalacturonan II (RG-II) and pectin assembly, which shows that B is essential for cell wall structure and function. The aim of the present work was to investigate the effects of B deficiency on the expression of cell wall-related genes in Arabidopsis roots. For this purpose, plants were grown hydroponically in a nutrient solution supplemented with 2 ?M B and then transferred to a boron-free medium for 6 and 24 h. A transcriptome analysis was carried out and several cell wall-related genes were identified, whose expressions were down-regulated by B deficiency. These genes belong to arabinogalactan protein, xyloglucan endotransglycosylase/hydrolase, polygalacturonase, pectate lyase, pectin methylesterase, expansin, and cellulose synthase-like gene families. These results suggest that in addition to the essential role that B plays in the structural organization of the cell wall, it could directly or indirectly have an impact on the expression levels of genes related to the cell wall.

Aging Cell
Jiménez-Hidalgo M, Santos-Ocaña C, Padilla S, Villalba JM, Lopez-Lluch G, Martín-Montalvo A, Minor RK, Sinclair DA, de Cabo R, Navas P.

The activity and expression of plasma membrane NADH coenzyme Q reductase is increased by calorie restriction (CR) in rodents. Although this effect is well established and is necessary for CR's ability to delay aging, the mechanism is unknown. Here we show that the Saccharomyces cerevisiae homolog, NQR1, resides at the plasma membrane and when overexpressed extends both replicative and chronological lifespan. We show that NQR1 extends replicative lifespan in a SIR2-dependent manner by shifting cells towards respiratory metabolism. Chronological lifespan extension, in contrast, occurs via a SIR2-independent decrease in ethanol production. We conclude that NQR1 is a key mediator of lifespan extension by CR through its effects on yeast metabolism and discuss how these findings could suggest a function for this protein in lifespan extension in mammals.

BBA Biomembranes
Padilla-López S, Jiménez-Hidalgo M, Martín-Montalvo A, Clarke CF, Navas P, Santos-Ocaña C.

Coenzyme Q is an isoprenylated benzoquinone lipid that functions in respiratory electron transport and as a lipid antioxidant. Dietary supplementation with Q is increasingly used as a therapeutic for treatment of mitochondrial and neurodegenerative diseases, yet little is known regarding the mechanism of its uptake. As opposed to other yeast backgrounds, EG103 strains are unable to import exogenous Q(6) to the mitochondria. Furthermore, the distribution of exogenous Q(6) among endomembranes suggests an impairment of the membrane traffic at the level of the endocytic pathway. This fact was confirmed after the detection of defects in the incorporation of FM4-64 marker and CPY delivery to the vacuole. A similar effect was demonstrated in double mutant strains in Q(6) synthesis and several steps of endocytic process; those cells are unable to uptake exogenous Q(6) to the mitochondria and restore the growth on non-fermentable carbon sources. Additional data about the positive effect of peptone presence for exogenous Q(6) uptake support the hypothesis that Q(6) is transported to mitochondria through an endocytic-based system.

Plant Science


To date, one asparagine synthetase (AS) mRNA has been identified in Nicotiana tabacum. Our results point out that this gene encodes an actual AS protein. This proposal is supported by the following facts. (i) Blast analysis indicates that tobacco AS gene shows increased percent identity with several AS genes of different plant species. (ii) Leaf and root AS mRNA levels were inversely correlated with soluble carbohydrate concentrations, both in the presence of light and in darkness, and the addition of exogenous sucrose repressed the root AS gene expression. (iii) In light, a positive correlation between AS transcript levels and ammonium content was observed in both leaves and roots. (iv) A direct correlation between leaf AS gene expression and asparagine (Asn) concentration has been found. Furthermore, quantitative real-time PCR analyses showed that this gene expression was increased under boron (B) deficiency in roots, but not in leaves. Interestingly, soluble B concentration in roots of plants subjected to B deficiency was significantly lower than that of control plants. However, in leaves, there was no significant difference in soluble B content between both B treatments. We discuss the possible role of soluble B deficiency in the regulation of AS gene expression in tobacco roots.
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