title: Cysteine dioxygenase and cysteine sulfinate decarboxylase genes of the deep-sea mussel Bathymodiolus septemdierum: possible involvement in hypotaurine synthesis and adaptation to hydrogen sulfide.
abstract: It has been suggested that invertebrates inhabiting deep-sea hydrothermal vent areas use the sulfinic acid hypotaurine, a precursor of taurine, to protect against the toxicity of hydrogen sulfide contained in the seawater from the vent. In this protective system, hypotaurine is accumulated in the gill, the primary site of sulfide exposure. However, the pathway for hypotaurine synthesis in mollusks has not been identified. In this study, we screened for the mRNAs of enzymes involved in hypotaurine synthesis in the deep-sea mussel Bathymodiolus septemdierum and cloned cDNAs encoding cysteine dioxygenase and cysteine sulfinate decarboxylase. As mRNAs encoding cysteamine dioxygenase and cysteine lyase were not detected, the cysteine sulfinate pathway is suggested to be the major pathway of hypotaurine and taurine synthesis. The two genes were found to be expressed in all the tissues examined, but the gill exhibited the highest expression. The mRNA level in the gill was not significantly changed by exposure to sulfides or thiosulfate. These results suggests that the gill of B. septemdierum maintains high levels of expression of the two genes regardless of ambient sulfide level and accumulates hypotaurine continuously to protect against sudden exposure to high level of sulfide.
authors.affiliation: Atmosphere and Ocean Research Institute, The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba, 277-8564, Japan.
authors.forename: Toshihiro
authors.initials: T
authors.lastname: Nagasaki
authors.forename: Yuki
authors.initials: Y
authors.lastname: Hongo
authors.forename: Tomoko
authors.initials: T
authors.lastname: Koito
authors.forename: Ikumi
authors.initials: I
authors.lastname: Nakamura-Kusakabe
authors.forename: Shigeru
authors.initials: S
authors.lastname: Shimamura
authors.forename: Yoshihiro
authors.initials: Y
authors.lastname: Takaki
authors.forename: Takao
authors.initials: T
authors.lastname: Yoshida
authors.forename: Tadashi
authors.initials: T
authors.lastname: Maruyama
authors.forename: Koji
authors.initials: K
authors.lastname: Inoue
mesh_terms: D000222:Adaptation, Physiological; D000818:Animals; D049872:Bivalvia / Q000201:enzymology / Q000235:genetics; D002262:Carboxy-Lyases / Q000096:biosynthesis / Q000235:genetics; D050558:Cysteine Dioxygenase / Q000096:biosynthesis / Q000235:genetics; D006862:Hydrogen Sulfide / Q000378:metabolism*; D013654:Taurine / Q000031:analogs & derivatives* / Q000096:biosynthesis / Q000235:genetics
chemical_list: D013654:Taurine; C003949:hypotaurine; D050558:Cysteine Dioxygenase; D002262:Carboxy-Lyases; C019972:sulfoalanine decarboxylase; D006862:Hydrogen Sulfide