title: Expression of a plant serine O-acetyltransferase in Saccharomyces cerevisiae confers osmotic tolerance and creates an alternative pathway for cysteine biosynthesis.
abstract: Screening of a sugar beet (Beta vulgaris cv. Dita) cDNA library for clones able to confer osmotic tolerance to the osmosensitive gpd1 mutant of Saccharomyces cerevisiae identified a novel serine O-acetyltransferase (BvSAT; EC 2.3.1.30). This enzyme is involved in cysteine biosynthesis in plants and bacteria, producing O-acetylserine, which is converted into cysteine in a reaction catalysed by O-acetylserine sulphydrylase (EC 4.2.99.8). This pathway is not conserved in yeast, where cysteine is synthesized in a four-step pathway starting with homoserine and having O-acetylhomoserine, homocysteine and cystathionine as intermediates. Expression of BvSAT in yeast takes advantage of the activity of yeast O-acetylhomoserine sulphydrylase (MET15/MET17/MET25; EC 4.2.99.10) with O-acetylserine as substrate and induces an alternative cysteine biosynthesis pathway. Our results imply that the resulting increase in cysteine production confers enhanced resistance against osmotic stress in the osmosensitive yeast strain. These data demonstrate that cysteine biosynthesis is a limiting factor in osmotic stress tolerance in yeast.
authors.affiliation: Instituto de Biología Molecular y Celular de Plantas, Universidad Politécnica de Valencia-CSIC, Avda de los Naranjos S/N, 46022 Valencia, Spain.
authors.forename: Jose M
authors.initials: JM
authors.lastname: Mulet
authors.forename: Beatriz
authors.initials: B
authors.lastname: Alemany
authors.forename: Roc
authors.initials: R
authors.lastname: Ros
authors.forename: Juan J
authors.initials: JJ
authors.lastname: Calvete
authors.forename: Ramon
authors.initials: R
authors.lastname: Serrano
mesh_terms: D000123:Acetyltransferases / Q000235:genetics*; D000596:Amino Acids / Q000032:analysis; D001483:Base Sequence; D027461:Beta vulgaris / Q000201:enzymology*; D003545:Cysteine / Q000096:biosynthesis*; D017931:DNA Primers; D018076:DNA, Complementary / Q000235:genetics; D018014:Gene Transfer Techniques; D008969:Molecular Sequence Data; D012441:Saccharomyces cerevisiae / Q000201:enzymology* / Q000235:genetics*; D051050:Serine O-Acetyltransferase; D013438:Sulfhydryl Compounds / Q000032:analysis
chemical_list: D000596:Amino Acids; D017931:DNA Primers; D018076:DNA, Complementary; D013438:Sulfhydryl Compounds; D000123:Acetyltransferases; D051050:Serine O-Acetyltransferase; D003545:Cysteine