title: Defects in a new class of sulfate/anion transporter link sulfur acclimation responses to intracellular glutathione levels and cell cycle control.
abstract: We previously identified a mutation, suppressor of mating type locus3 15-1 (smt15-1), that partially suppresses the cell cycle defects caused by loss of the retinoblastoma tumor suppressor-related protein encoded by the MAT3 gene in Chlamydomonas reinhardtii. smt15-1 single mutants were also found to have a cell cycle defect leading to a small-cell phenotype. SMT15 belongs to a previously uncharacterized subfamily of putative membrane-localized sulfate/anion transporters that contain a sulfate transporter domain and are found in a widely distributed subset of eukaryotes and bacteria. Although we observed that smt15-1 has a defect in acclimation to sulfur-limited growth conditions, sulfur acclimation (sac) mutants, which are more severely defective for acclimation to sulfur limitation, do not have cell cycle defects and cannot suppress mat3. Moreover, we found that smt15-1, but not sac mutants, overaccumulates glutathione. In wild-type cells, glutathione fluctuated during the cell cycle, with highest levels in mid G1 phase and lower levels during S and M phases, while in smt15-1, glutathione levels remained elevated during S and M. In addition to increased total glutathione levels, smt15-1 cells had an increased reduced-to-oxidized glutathione redox ratio throughout the cell cycle. These data suggest a role for SMT15 in maintaining glutathione homeostasis that impacts the cell cycle and sulfur acclimation responses.
authors.affiliation: Biotechnology Center in Southern Taiwan, Academia Sinica, Tainan County 741, Taiwan (S.-C.F., C.-L.C., C.-H.C.);Agricultural Biotechnology Research Center, Academia Sinica, Taipei 115, Taiwan (S.-C.F., C.-L.C., C.-H.C.);Institute of Marine Biotechnology, National Sun Yat-sen University, Kaohsiung 80424, Taiwan (C.-L.C.); andDonald Danforth Plant Science Center, St. Louis, Missouri 63132 (C.L.-P., J.G.U.) scfang@gate.sinica.edu.tw jumen@danforthcenter.org.
authors.forename: Su-Chiung
authors.initials: SC
authors.lastname: Fang
authors.affiliation: Biotechnology Center in Southern Taiwan, Academia Sinica, Tainan County 741, Taiwan (S.-C.F., C.-L.C., C.-H.C.);Agricultural Biotechnology Research Center, Academia Sinica, Taipei 115, Taiwan (S.-C.F., C.-L.C., C.-H.C.);Institute of Marine Biotechnology, National Sun Yat-sen University, Kaohsiung 80424, Taiwan (C.-L.C.); andDonald Danforth Plant Science Center, St. Louis, Missouri 63132 (C.L.-P., J.G.U.).
authors.forename: Chin-Lin
authors.initials: CL
authors.lastname: Chung
authors.affiliation: Biotechnology Center in Southern Taiwan, Academia Sinica, Tainan County 741, Taiwan (S.-C.F., C.-L.C., C.-H.C.);Agricultural Biotechnology Research Center, Academia Sinica, Taipei 115, Taiwan (S.-C.F., C.-L.C., C.-H.C.);Institute of Marine Biotechnology, National Sun Yat-sen University, Kaohsiung 80424, Taiwan (C.-L.C.); andDonald Danforth Plant Science Center, St. Louis, Missouri 63132 (C.L.-P., J.G.U.).
authors.forename: Chun-Han
authors.initials: CH
authors.lastname: Chen
authors.affiliation: Biotechnology Center in Southern Taiwan, Academia Sinica, Tainan County 741, Taiwan (S.-C.F., C.-L.C., C.-H.C.);Agricultural Biotechnology Research Center, Academia Sinica, Taipei 115, Taiwan (S.-C.F., C.-L.C., C.-H.C.);Institute of Marine Biotechnology, National Sun Yat-sen University, Kaohsiung 80424, Taiwan (C.-L.C.); andDonald Danforth Plant Science Center, St. Louis, Missouri 63132 (C.L.-P., J.G.U.).
authors.forename: Cristina
authors.initials: C
authors.lastname: Lopez-Paz
authors.affiliation: Biotechnology Center in Southern Taiwan, Academia Sinica, Tainan County 741, Taiwan (S.-C.F., C.-L.C., C.-H.C.);Agricultural Biotechnology Research Center, Academia Sinica, Taipei 115, Taiwan (S.-C.F., C.-L.C., C.-H.C.);Institute of Marine Biotechnology, National Sun Yat-sen University, Kaohsiung 80424, Taiwan (C.-L.C.); andDonald Danforth Plant Science Center, St. Louis, Missouri 63132 (C.L.-P., J.G.U.) scfang@gate.sinica.edu.tw jumen@danforthcenter.org.
authors.forename: James G
authors.initials: JG
authors.lastname: Umen
mesh_terms: D000064:Acclimatization; D020418:Algal Proteins / Q000235:genetics / Q000378:metabolism*; D027321:Anion Transport Proteins / Q000235:genetics / Q000378:metabolism; D000838:Anions / Q000378:metabolism; D001483:Base Sequence; D002453:Cell Cycle; D059447:Cell Cycle Checkpoints; D016825:Chlamydomonas reinhardtii / Q000235:genetics / Q000502:physiology*; D003593:Cytoplasm / Q000378:metabolism; D005978:Glutathione / Q000378:metabolism*; D059014:High-Throughput Nucleotide Sequencing; D008969:Molecular Sequence Data; D009154:Mutation; D010802:Phylogeny; D017423:Sequence Analysis, RNA; D013431:Sulfates / Q000378:metabolism; D013455:Sulfur / Q000378:metabolism*
chemical_list: D020418:Algal Proteins; D027321:Anion Transport Proteins; D000838:Anions; D013431:Sulfates; D013455:Sulfur; D005978:Glutathione