title: Impact of Sulfur Starvation in Autotrophic and Heterotrophic Cultures of the Extremophilic Microalga Galdieria phlegrea (Cyanidiophyceae).
abstract: In plants and algae, sulfate assimilation and cysteine synthesis are regulated by sulfur (S) accessibility from the environment. This study reports the effects of S deprivation in autotrophic and heterotrophic cultures of Galdieria phlegrea (Cyanidiophyceae), a unicellular red alga isolated in the Solfatara crater located in Campi Flegrei (Naples, Italy), where H2S is the prevalent form of gaseous S in the fumarolic fluids and S is widespread in the soils near the fumaroles. This is the first report on the effects of S deprivation on a sulfurous microalga that is also able to grow heterotrophically in the dark. The removal of S from the culture medium of illuminated cells caused a decrease in the soluble protein content and a significant decrease in the intracellular levels of glutathione. Cells from heterotrophic cultures of G. phlegrea exhibited high levels of internal proteins and high glutathione content, which did not diminish during S starvation, but rather glutathione significantly increased. The activity of O-acetylserine(thiol)lyase (OASTL), the enzyme synthesizing cysteine, was enhanced under S deprivation in a time-dependent manner in autotrophic but not in heterotrophic cells. Analysis of the transcript abundance of the OASTL gene supports the OASTL activity increase in autotrophic cultures under S deprivation.
authors.affiliation: Department of Biology, University of Naples Federico II, Via Foria 223, I-80139 Naples, Italy simcarfa@unina.it.
authors.forename: Simona
authors.initials: S
authors.lastname: Carfagna
authors.affiliation: Department of Biology, University of Naples Federico II, Via Foria 223, I-80139 Naples, Italy.
authors.forename: Claudia
authors.initials: C
authors.lastname: Bottone
authors.affiliation: Department of Biology, University of Naples Federico II, Via Foria 223, I-80139 Naples, Italy.
authors.forename: Pia Rosa
authors.initials: PR
authors.lastname: Cataletto
authors.affiliation: Consiglio per la Ricerca e la Sperimentazione in Agricoltura, Unità di ricerca per la Frutticoltura, Via Torrino 2, I-81100 Caserta, Italy.
authors.forename: Milena
authors.initials: M
authors.lastname: Petriccione
authors.affiliation: Department of Biology, University of Naples Federico II, Via Foria 223, I-80139 Naples, Italy.
authors.forename: Gabriele
authors.initials: G
authors.lastname: Pinto
authors.affiliation: Department of Biology, University of Naples Federico II, Via Foria 223, I-80139 Naples, Italy.
authors.forename: Giovanna
authors.initials: G
authors.lastname: Salbitani
authors.affiliation: Department of Biology, University of Naples Federico II, Via Foria 223, I-80139 Naples, Italy.
authors.forename: Vincenza
authors.initials: V
authors.lastname: Vona
authors.affiliation: Department of Biology, University of Naples Federico II, Via Foria 223, I-80139 Naples, Italy.
authors.forename: Antonino
authors.initials: A
authors.lastname: Pollio
authors.affiliation: Department of Biological and Pharmaceutical Science and Technology, Second University of Naples, Via Vivaldi 43, I-81100 Caserta, Italy.
authors.forename: Claudia
authors.initials: C
authors.lastname: Ciniglia
mesh_terms: D052818:Autotrophic Processes; D019757:Carbon-Oxygen Lyases / Q000235:genetics / Q000378:metabolism; D003545:Cysteine / Q000096:biosynthesis; D052836:Heterotrophic Processes; D058086:Microalgae / Q000254:growth & development* / Q000378:metabolism*; D011506:Proteins / Q000378:metabolism; D000461:Rhodophyta / Q000254:growth & development* / Q000378:metabolism*; D013438:Sulfhydryl Compounds / Q000378:metabolism; D013455:Sulfur / Q000378:metabolism*
chemical_list: D011506:Proteins; D013438:Sulfhydryl Compounds; D013455:Sulfur; C018725:O-acetylhomoserine (thiol)-lyase; D019757:Carbon-Oxygen Lyases; D003545:Cysteine
keywords: Cyanidiophyceae; Galdieria phlegrea; Glutathione; Heterotrophic cultures; O-Acetylserine(thiol)lyase; Sulfur deficiency