Polytechnic University of Valencia

About: Polytechnic University of Valencia is a education organization based out in Valencia, Spain. It is known for research contribution in the topics: Catalysis & Population. The organization has 16282 authors who have published 40162 publications receiving 850234 citations.

Repressors and Upstream Repressing Sequences of the Stress- Regulated ENA1 Gene in Saccharomyces cerevisiae: bZIP Protein Sko1p Confers HOG-Dependent Osmotic Regulation

Abstract: The study of adaptation mechanisms during salinity stress in the yeast Saccharomyces cerevisiae has revealed several components of sensing and signal transduction pathways, as well as target genes whose expression is activated upon salt stress (for review see references 18, 45, and 46). Increased expression of the ENA1 gene has been found to represent a crucial cellular response after salt challenge. The ENA/PMR2 gene cluster of S. cerevisiae contains a tandem array of nearly identical genes encoding P-type ATPases involved in the extrusion of Na+ and Li+ ions from the cytoplasm (17, 59). Active export of these toxic ions is a crucial cellular process to avoid deleterious intracellular Na+ and Li+ concentrations. Mutants lacking the first ENA gene in the gene cluster (ena1) are hypersensitive to salt stress (17). The ENA1 gene is highly regulated at the transcriptional level, and its expression is increased strongly in response to salt stress (12) and glucose starvation (1, 41). Salt induction of ENA1 expression depends on both the calcineurin pathway and the high-osmolarity glycerol (HOG) mitogen-activated protein (MAP) kinase pathway (28). The first pathway is activated by high concentrations of either Na+ or Ca2+ and is dependent on the phosphoprotein phosphatase calcineurin (28, 33). A calcium signalling pathway composed of calmodulin (7), the calcineurin heterodimeric enzyme (6, 23), and the zinc finger transcriptional activator Crz1/Tcn1/Hal8p (31, 32, 50) has been reported to contribute to the resistance of yeast to elevated concentrations of several cations (Na+, Li+, and Mn2+). Therefore, Ca2+/calmodulin signalling may act, at least in part, through the transcriptional activation of ion transporter genes such as ENA1. The HOG pathway responds to moderate concentrations of osmotic agents and rapidly activates via a multistep phosphorelay mechanism the Hog1p MAP kinase by Tyr phosphorylation (2, 26, 39). Although a great number of genes have been found to need HOG signalling for their osmotic up-regulation, the mechanism of gene activation through phosphorylated Hog1p kinase is still unknown. In Schizosaccharomyces pombe, the basic leucine zipper (bZIP) transcriptional activator Atf1p has been identified as a direct phosphorylation target of the Hog1p homolog MAP kinase Sty1p (49, 51, 60). Activated Atf1p, in turn, can bind directly to UASs (upstream activating sequences) located in various stress-regulated promoters and then trigger gene expression (60). In S. cerevisiae, stress response promoter elements (STREs) represent UASs that respond to a great variety of stresses (22, 27, 43) and are bound by the zinc finger activators Msn2p and Msn4p (30, 42). Recent work, however, indicates that osmotic induction of several genes including ENA1 occurs by the release from transcriptional repression (29) and involves the general repressor complex Ssn6p-Tup1p. In the case of the HAL1 gene, an upstream repressing sequence (URS) regulated by osmotic stress has been identified (29). This mechanism based on regulated repressors bound to URSs is similar to the one operating in carbon source regulation. A great number of yeast genes, including ENA1, are derepressed under glucose starvation conditions, and for many of them the inactivation of the general repressor complex Mig1p-Ssn6p-Tup1p (21, 36, 54) through the protein kinase Snf1p (3, 53) has been reported as an important mechanism of glucose-regulated transcriptional control. In this work, we analyzed the promoter of the ENA1 gene and found that transcriptional regulation during osmotic stress as well as during glucose starvation occurs through a repression mechanism dependent on the Ssn6p-Tup1p general corepressor. Signalling through general glucose repression occurs through a Mig1/2p binding site (URSMIG-ENA1), whereas osmotic stress signalling through the HOG pathway is mediated through a cyclic AMP (cAMP) response element (CRE)-like sequence (URSCRE-ENA1) that is bound by the bZIP transcriptional factor Sko1p.

Composts from distillery wastes as peat substitutes for transplant production

Abstract: The use of composts from distillery wastes as alternative growing media ingredients for transplant production instead of peat, whose harvesting constitutes a severe environmental damage, was studied. Two composts were prepared with exhausted grape marc and cattle manure (C1), and with exhausted grape marc and poultry manure (C2). Four vegetable species, lettuce ( Lactuca sativa ), chard ( Beta vulgaris ), broccoli ( Brassica oleracea ) and coriander ( Coriandrum sativum ) were grown. Nine substrates were compared: limed white peat (control); compost C1; compost C2; and six mixtures containing 25%, 50% and 75% by volume of each compost with the corresponding peat as diluent. The germination and the effects on the transplant morphological and nutritional aspects of the different mixtures peat/compost considered were studied. All media elaborated showed adequate physical, physico-chemical and chemical properties compared to peat for their use as growing media in horticulture, being these two composts suitable ingredients for the partial substitution of peat, in quantities of 25–50% by volume, without causing any loss in the yield and in the results obtained for the nutritional status when compared to those obtained using the control.

Arabidopsis m6A demethylase activity modulates viral infection of a plant virus and the m6A abundance in its genomic RNAs.

Abstract: N6-methyladenosine (m6A) is an internal, reversible nucleotide modification that constitutes an important regulatory mechanism in RNA biology. Unlike mammals and yeast, no component of the m6A cellular machinery has been described in plants at present. m6A has been identified in the genomic RNAs of diverse mammalian viruses and, additionally, viral infection was found to be modulated by the abundance of m6A in viral RNAs. Here we show that the Arabidopsis thaliana protein atALKBH9B (At2g17970) is a demethylase that removes m6A from single-stranded RNA molecules in vitro. atALKBH9B accumulates in cytoplasmic granules, which colocalize with siRNA bodies and associate with P bodies, suggesting that atALKBH9B m6A demethylase activity could be linked to mRNA silencing and/or mRNA decay processes. Moreover, we identified the presence of m6A in the genomes of two members of the Bromoviridae family, alfalfa mosaic virus (AMV) and cucumber mosaic virus (CMV). The demethylation activity of atALKBH9B affected the infectivity of AMV but not of CMV, correlating with the ability of atALKBH9B to interact (or not) with their coat proteins. Suppression of atALKBH9B increased the relative abundance of m6A in the AMV genome, impairing the systemic invasion of the plant, while not having any effect on CMV infection. Our findings suggest that, as recently found in animal viruses, m6A modification may represent a plant regulatory strategy to control cytoplasmic-replicating RNA viruses.

Graphenes in the absence of metals as carbocatalysts for selective acetylene hydrogenation and alkene hydrogenation

Abstract: Hydrogenation of carbon-carbon multiple bonds is an industrially important process, usually involving metallic catalysts. Here, the authors show that graphene based catalysts can also catalyse alkene and acetylene hydrogenation.