title: The mechanism of improved intracellular organic selenium and glutathione contents in selenium-enriched Candida utilis by acid stress.
abstract: Batch culture of Candida utilis CCTCC M 209298 for the preparation of selenium (Se)-enriched yeast was carried out under different pH conditions, and maximal intracellular organic Se and glutathione (GSH) contents were obtained in a moderate acid stress environment (pH 3.5). In order to elucidate the physiological mechanism of improved performance of Se-enriched yeast by acid stress, assays of the key enzymes involved in GSH biosynthesis and determinations of energy supply and regeneration were performed. The results indicated that moderate acid stress increased the activity of γ-glutamylcysteine synthetase and the ratios of NADH/NAD+and ATP/ADP, although no significant changes in intracellular pH were observed. In addition, the molecular mechanism of moderate acid stress favoring the improvement of Se-yeast performance was revealed by comparing whole transcriptomes of yeast cells cultured at pH 3.5 and 5.5. Comparative analysis of RNA-Seq data indicated that 882 genes were significantly up-regulated by moderate acid stress. Functional annotation of the up-regulated genes based on gene ontology and the Kyoto Encyclopedia of Genes and Genome (KEGG) pathway showed that these genes are involved in ATP synthesis and sulfur metabolism, including the biosynthesis of methionine, cysteine, and GSH in yeast cells. Increased intracellular ATP supply and more amounts of sulfur-containing substances in turn contributed to Na2SeO3assimilation and biotransformation, which ultimately improved the performance of the Se-enriched C. utilis.
authors.affiliation: School of Biology and Basic Medical Sciences, Soochow University, Suzhou, 215123, People's Republic of China.
authors.forename: Gao-Chuan
authors.initials: GC
authors.lastname: Zhang
authors.affiliation: School of Biology and Basic Medical Sciences, Soochow University, Suzhou, 215123, People's Republic of China.
authors.forename: Da-Hui
authors.initials: DH
authors.lastname: Wang
authors.affiliation: School of Biology and Basic Medical Sciences, Soochow University, Suzhou, 215123, People's Republic of China.
authors.forename: Dong-Hua
authors.initials: DH
authors.lastname: Wang
authors.affiliation: School of Biology and Basic Medical Sciences, Soochow University, Suzhou, 215123, People's Republic of China. weigy@suda.edu.cn.
authors.forename: Gong-Yuan
authors.initials: GY
authors.lastname: Wei
mesh_terms: D000255:Adenosine Triphosphate / Q000096:biosynthesis; D002175:Candida / Q000235:genetics / Q000378:metabolism*; D003545:Cysteine / Q000096:biosynthesis; D005721:Glutamate-Cysteine Ligase / Q000378:metabolism*; D005978:Glutathione / Q000096:biosynthesis / Q000378:metabolism*; D008715:Methionine / Q000096:biosynthesis; D012643:Selenium / Q000378:metabolism*; D018036:Selenium Compounds / Q000378:metabolism*; D013455:Sulfur / Q000378:metabolism; D059467:Transcriptome / Q000235:genetics
chemical_list: D018036:Selenium Compounds; D013455:Sulfur; D000255:Adenosine Triphosphate; D008715:Methionine; D005721:Glutamate-Cysteine Ligase; D005978:Glutathione; D012643:Selenium; D003545:Cysteine
keywords: ATP; Acid stress; Candida utilis; Glutathione; RNA-Seq; Selenium-enriched yeast