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Sulfur Deficiency (sulfur + deficiency)
Selected AbstractsSulfur assimilation and glutathione metabolism under cadmium stress in yeast, protists and plantsFEMS MICROBIOLOGY REVIEWS, Issue 4 2005David Mendoza-Cózatl Abstract Glutathione (,-glu-cys-gly; GSH) is usually present at high concentrations in most living cells, being the major reservoir of non-protein reduced sulfur. Because of its unique redox and nucleophilic properties, GSH serves in bio-reductive reactions as an important line of defense against reactive oxygen species, xenobiotics and heavy metals. GSH is synthesized from its constituent amino acids by two ATP-dependent reactions catalyzed by ,-glutamylcysteine synthetase and glutathione synthetase. In yeast, these enzymes are found in the cytosol, whereas in plants they are located in the cytosol and chloroplast. In protists, their location is not well established. In turn, the sulfur assimilation pathway, which leads to cysteine biosynthesis, involves high and low affinity sulfate transporters, and the enzymes ATP sulfurylase, APS kinase, PAPS reductase or APS reductase, sulfite reductase, serine acetyl transferase, O -acetylserine/O -acetylhomoserine sulfhydrylase and, in some organisms, also cystathionine ,-synthase and cystathionine ,-lyase. The biochemical and genetic regulation of these pathways is affected by oxidative stress, sulfur deficiency and heavy metal exposure. Cells cope with heavy metal stress using different mechanisms, such as complexation and compartmentation. One of these mechanisms in some yeast, plants and protists is the enhanced synthesis of the heavy metal-chelating molecules GSH and phytochelatins, which are formed from GSH by phytochelatin synthase (PCS) in a heavy metal-dependent reaction; Cd2+ is the most potent activator of PCS. In this work, we review the biochemical and genetic mechanisms involved in the regulation of sulfate assimilation-reduction and GSH metabolism when yeast, plants and protists are challenged by Cd2+. [source] Sulfur Deficiency Changes Mycosporine-like Amino Acid (MAA) Composition of Anabaena variabilis PCC 7937: A Possible Role of Sulfur in MAA BioconversionPHOTOCHEMISTRY & PHOTOBIOLOGY, Issue 4 2010Shailendra P. Singh In the present investigation we show for the first time that bioconversion of a primary mycosporine-like amino acid (MAA) into a secondary MAA is regulated by sulfur deficiency in the cyanobacterium Anabaena variabilis PCC 7937. This cyanobacterium synthesizes the primary MAA shinorine (RT = 2.2 min, ,max = 334 nm) under normal conditions (PAR + UV-A + UV-B); however, under sulfur deficiency, a secondary MAA palythine-serine (RT = 3.9 min, ,max = 320 nm) appears. Addition of methionine to sulfur-deficient cultures resulted in the disappearance of palythine-serine, suggesting the role of primary MAAs under sulfur deficiency in recycling of methionine by donating the methyl group from the glycine subunit of shinorine to tetrahydrofolate to regenerate the methionine from homocysteine. This is also the first report for the synthesis of palythine-serine by cyanobacteria which has so far been reported only from corals. Addition of methionine also affected the conversion of mycosporine-glycine into shinorine, consequently, resulted in the appearance of mycosporine-glycine (RT = 3.6 min, ,max = 310 nm). Our results also suggest that palythine-serine is synthesized from shinorine. Based on these results we propose that glycine decarboxylase is the potential enzyme that catalyzes the bioconversion of shinorine to palythine-serine by decarboxylation and demethylation of the glycine unit of shinorine. [source] The function of SULTR2;1 sulfate transporter during seed development in Arabidopsis thalianaPHYSIOLOGIA PLANTARUM, Issue 1 2005Motoko Awazuhara SULTR2;1 is a low-affinity sulfate transporter expressed in the vascular tissues of roots and leaves for interorgan transport of sulfate in Arabidopsis thaliana. Transgenic Arabidopsis carrying a fusion gene construct of SULTR2;1 5,-promoter region and ,-glucuronidase coding sequence (GUS) demonstrated that within the reproductive tissues, SULTR2;1 is specifically expressed in the bases and veins of siliques and in the funiculus, which connects the seeds and the silique. The antisense suppression of SULTR2;1 mRNA caused decrease of sulfate contents in seeds and of thiol contents both in seeds and leaves, as compared with the wildtype (WT). The effect of antisense suppression of SULTR2;1 on seed sulfur status was determined by introducing a sulfur-indicator construct, p35S::,SRx3:GUS, which drives the expression of GUS reporter under a chimeric cauliflower mosaic virus 35S promoter containing a triplicate repeat of sulfur-responsive promoter region of soybean ,-conglycinin , subunit (,SRx3). The mature seeds of F1 plants carrying both the SULTR2;1 antisense and p35S::,SRx3:GUS constructs exhibited significant accumulation of GUS activities on sulfur deficiency, as compared with those carrying only the p35S::,SRx3:GUS construct in the WT background. These results suggested that SULTR2;1 is involved in controlling translocation of sulfate into developing siliques and may modulate the sulfur status of seeds in A. thaliana. [source] Identification of a novel cis -acting element conferring sulfur deficiency response in Arabidopsis rootsTHE PLANT JOURNAL, Issue 3 2005Akiko Maruyama-Nakashita Summary SULTR1;1 high-affinity sulfate transporter is highly regulated in the epidermis and cortex of Arabidopsis roots responding to sulfur deficiency (,S). We identified a novel cis -acting element involved in the ,S-inducible expression of sulfur-responsive genes in Arabidopsis. The promoter region of SULTR1;1 was dissected for deletion and gain-of-function analysis using luciferase (LUC) reporter gene in transgenic Arabidopsis. The 16-bp sulfur-responsive element (SURE) from ,2777 to ,2762 of SULTR1;1 promoter was sufficient and necessary for the ,S-responsive expression, which was reversed when supplied with cysteine and glutathione (GSH). The SURE sequence contained an auxin response factor (ARF) binding sequence (GAGACA). However, SURE was not responsive to naphthalene acetic acid, indicating its specific function in the sulfur response. The base substitution analysis indicated the significance of a 5-bp sequence (GAGAC) within the conserved ARF binding site as a core element for the ,S response. Microarray analysis of early ,S response in Arabidopsis roots indicated the presence of SURE core sequences in the promoter regions of ,S-inducible genes on a full genome GeneChip array. It is suggested that SURE core sequences may commonly regulate the expression of a gene set required for adaptation to the ,S environment. [source] Modeling and Optimization of Photosynthetic Hydrogen Gas Production by Green Alga Chlamydomonas reinhardtii in Sulfur-Deprived CircumstanceBIOTECHNOLOGY PROGRESS, Issue 2 2006Ji Hye Jo Biological hydrogen production by the green alga Chlamydomonas reinhardtii under sulfur-deprived conditions has attracted great interest due to the fundamental and practical importance of the process. The photosynthetic hydrogen production rate is dependent on various factors such as strain type, nutrient composition, temperature, pH, and light intensity. In this study, physicochemical factors affecting biological hydrogen production by C. reinhardtii were evaluated with response surface methodology (RSM). First, the maximum specific growth rate of the alga associated with simultaneous changes of ammonium, phosphate, and sulfate concentrations in the culture medium were investigated. The optimum conditions were determined as NH4+ 8.00 mM, PO43, 1.11 mM, and SO42, 0.79 mM in Tris-acetate-phosphate (TAP) medium. The maximum specific growth rate with the optimum nutrient concentrations was 0.0373 h,1. Then, the hydrogen production rate of C. reinhardtii under sulfur-deprivation conditions was investigated by simultaneously changing two nutrient concentrations and pH in the medium. The maximum hydrogen production was 2.152 mL of H2 for a 10-mL culture of alga with density of 6 × 106 cells mL,1 for 96 h under conditions of NH4+ 9.20 mM, PO43, 2.09 mM, and pH 7.00. The obtained hydrogen production rate was approximately 1.55 times higher than that with the typical TAP medium under sulfur deficiency. [source] | ||||||||||