title: GAS2 and GAS4, a pair of developmentally regulated genes required for spore wall assembly in Saccharomyces cerevisiae.
abstract: The GAS multigene family of Saccharomyces cerevisiae is composed of five paralogs (GAS1 to GAS5). GAS1 is the only one of these genes that has been characterized to date. It encodes a glycosylphosphatidylinositol-anchored protein functioning as a beta(1,3)-glucan elongase and required for proper cell wall assembly during vegetative growth. In this study, we characterize the roles of the GAS2 and GAS4 genes. These genes are expressed exclusively during sporulation. Their mRNA levels showed a peak at 7 h from induction of sporulation and then decreased. Gas2 and Gas4 proteins were detected and reached maximum levels between 8 and 10 h from induction of sporulation, a time roughly coincident with spore wall assembly. The double null gas2 gas4 diploid mutant showed a severe reduction in the efficiency of sporulation, an increased permeability of the spores to exogenous substances, and production of inviable spores, whereas the single gas2 and gas4 null diploids were similar to the parental strain. An analysis of spore ultrastructure indicated that the loss of Gas2 and Gas4 proteins affected the proper attachment of the glucan to the chitosan layer, probably as a consequence of the lack of coherence of the glucan layer. The ectopic expression of GAS2 and GAS4 genes in a gas1 null mutant revealed that these proteins are redundant versions of Gas1p specialized to function in a compartment at a pH value close to neutral.
authors.affiliation: Dipartimento di Scienze Biomolecolari e Biotecnologie, Università degli Studi di Milano, Via Celoria 26, 20133 Milano, Italy.
authors.forename: Enrico
authors.initials: E
authors.lastname: Ragni
authors.forename: Alison
authors.initials: A
authors.lastname: Coluccio
authors.forename: Eleonora
authors.initials: E
authors.lastname: Rolli
authors.forename: José Manuel
authors.initials: JM
authors.lastname: Rodriguez-Peña
authors.forename: Gaia
authors.initials: G
authors.lastname: Colasante
authors.forename: Javier
authors.initials: J
authors.lastname: Arroyo
authors.forename: Aaron M
authors.initials: AM
authors.lastname: Neiman
authors.forename: Laura
authors.initials: L
authors.lastname: Popolo
mesh_terms: D002473:Cell Wall / Q000502:physiology*; D018507:Gene Expression Regulation, Developmental; D015966:Gene Expression Regulation, Fungal; D005816:Genetic Complementation Test; D008540:Meiosis; D010957:Plasmids; D016133:Polymerase Chain Reaction; D012331:RNA, Fungal / Q000235:genetics / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism*; D013172:Spores, Fungal / Q000737:chemistry / Q000502:physiology*
chemical_list: D012331:RNA, Fungal; D029701:Saccharomyces cerevisiae Proteins