We analyzed the effects of deprivation and subsequent restoration of sulphate (S) in the nutrient solution on cysteine (Cys) and O-acetyl-L-serine (OAS) levels in Chlorella sorokiniana (211/8k). The removal of S from the culture medium caused a time-dependent increase in O-acetyl-L-serine(thiol)lyase (OASTL) activity and a decrease in soluble proteins content. The protein gel blot analysis was used to show that OASTL isoforms are located in the chloroplast and in the cytoplasm of S-starved cells. S-deprivation caused a decrease in the intracellular levels of Cys and glutathione (GSH) and an increase in serine (Ser) and OAS, reflecting an imbalance between sulphur and nitrogen assimilation. Re-supplying of sulphate to S-starved cells produced a decrease in OAS levels and concomitant rapid increase in Cys and GSH concentrations. The simultaneous addition of OAS and sulphate to S-starved cells did not further increase the concentration of Cys, suggesting the existence of a threshold level of intracellular Cys that is independent of the cellular concentration of OAS. Our findings that OAS is stored during S-starvation and that its quick decrease appears to be coupled with the increase of Cys levels upon re-supply of sulphate, imply that the central role that these two compounds play is in the regulation of sulphur-assimilating enzymes in response to the S status of the cell.
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Sci Rep
December 2019
School of Life Sciences, Tokyo University of Pharmacy and Life Sciences, Hachioji, Tokyo, 192-0392, Japan.
Poly-β-hydroxybutyrate (PHB) in cyanobacteria, which accumulates as energy and carbon sources through the action of photosynthesis, is expected to substitute for petroleum-based plastics. This study first demonstrated that PHB accumulation was induced, with the appearance of lipid droplets, in sulfur (S)-starved cells of a cyanobacterium, Synechocystis sp. PCC 6803, however, to a lower level than in nitrogen (N)- or phosphorus (P)-starved cells.
View Article and Find Full Text PDFFront Plant Sci
October 2014
School of Life Sciences, Tokyo University of Pharmacy and Life Sciences Hachioji, Japan ; Japan Science and Technology Agency, Core Research for Evolutionary Science and Technology Chiyoda-ku, Japan.
Triacylglycerol (TG) synthesis is induced for energy and carbon storage in algal cells under nitrogen(N)-starved conditions, and helps prevent reactive oxygen species (ROS) production through fatty acid synthesis that consumes excessive reducing power. Here, the regulatory mechanism for the TG content in sulfur(S)-starved cells of Chlamydomonas reinhardtii was examined, in comparison to that in N- or phosphorus(P)-starved cells. S- and N- starved cells exhibited markedly increased TG contents with up-regulation of mRNA levels of diacylglycerol acyltransferase (DGAT) genes.
View Article and Find Full Text PDFMetabolites
August 2014
Dipartimento di Biologia, Università di Napoli Federico II, Via Foria 223, I-80139 Napoli, Italy.
In the unicellular green alga Chlorella sorokiniana (211/8 k), the protein O-acetylserine(thiol)lyase (OASTL), representing the key-enzyme in the biosynthetic cysteine pathway, was isolated and purified to apparent homogeneity. The purification was carried out in cells grown in the presence of all nutrients or in sulphate (S) deprived cells. After 24 h of S-starvation, a 17-fold increase in the specific activity of OASTL was measured.
View Article and Find Full Text PDFBioengineered
March 2013
Laboratory of Sustainable Technologies; UNAM Institute of Materials Science and Nanotechnology, Bilkent University, Ankara, Turkey.
Nitrogen (N) and sulfur (S) have inter-related and distinct impacts on microalgal metabolism; with N starvation having previously been reported to induce elevated levels of the biodiesel feedstock material triacylglycerol (TAG), while S deprivation is extensively studied for its effects on biohydrogen production in microalgae. ( 1) (,) ( 2) We have previously demonstrated that N- and S-starved cells of Chlamydomonas reinhardtii display different metabolic trends, suggesting that different response mechanisms exist to compensate for the absence of those two elements. ( 3) We used C.
View Article and Find Full Text PDFBiophys J
February 2012
Department of Physiology and Biophysics, University of Arkansas for Medical Sciences, Little Rock, Arkansas, USA.
Saccharomyces cerevisiae SO(4)(=) transport is regulated over a wide dynamic range. Sulfur starvation causes ∼10,000-fold increase in the (35)SO(4)(=) influx mediated by transporters Sul1p and Sul2p; >80% of the influx is via Sul2p. Adding methionine to S-starved cells causes a 50-fold decline (t(1/2) ∼5 min) in SUL1 and SUL2 mRNA but a slower decline (t(1/2) ∼1 h) in transport.
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