title: Role of the Cytosolic Heat Shock Protein 70 Ssa5 in the Ciliate Protozoan Tetrahymena thermophila.
abstract: Heat shock protein 70 (Hsp70) is a member of a family of conserved chaperone proteins whose function is well investigated in many model organisms. Here we focus on an Hsp70 called Ssa5 in the ciliate protozoan Tetrahymena thermophila, and reveal that its translation is heat inducible as for general Hsps. Moreover, the protein is abundantly expressed in the cytoplasm during sexual reproduction (conjugation) as well as in response to heat-stress. Knocking out of SSA5 (ΔSSA5) does not affect the survival of the cell under heat-stress, likely due to other Hsp70 paralogs compensating for the defect. During conjugation, ΔSSA5 leads to a fertilization defect in which the two pronuclei are in close proximity but never fuse. The unfertilized pronuclei differentiate, resulting in a heterokaryon with developed haploid germline and somatic nuclei. In addition, degeneration of the parental somatic nucleus is not affected. These results suggest a specific involvement of Ssa5 in pronuclear fusion and fertilization.
authors.affiliation: Department of Biodiversity Science, Division of Biological Resource Science, Graduate School of Agricultural Science, Tohoku University, Osaki, Japan.
authors.forename: Yasuhiro
authors.initials: Y
authors.lastname: Fukuda
authors.affiliation: Department of Biology, York University, Toronto, Ontario, Canada.
authors.forename: Takahiko
authors.initials: T
authors.lastname: Akematsu
authors.affiliation: Department of Biology, York University, Toronto, Ontario, Canada.
authors.forename: Rizwan
authors.initials: R
authors.lastname: Attiq
authors.affiliation: Department of Biodiversity Science, Division of Biological Resource Science, Graduate School of Agricultural Science, Tohoku University, Osaki, Japan.
authors.forename: Chika
authors.initials: C
authors.lastname: Tada
authors.affiliation: Department of Biodiversity Science, Division of Biological Resource Science, Graduate School of Agricultural Science, Tohoku University, Osaki, Japan.
authors.forename: Yutaka
authors.initials: Y
authors.lastname: Nakai
authors.affiliation: Department of Biology, York University, Toronto, Ontario, Canada.
authors.forename: Ronald E
authors.initials: RE
authors.lastname: Pearlman
mesh_terms: D000818:Animals; D002467:Cell Nucleus; D003227:Conjugation, Genetic; D003593:Cytoplasm / Q000737:chemistry; D055786:Gene Knockout Techniques; D018840:HSP70 Heat-Shock Proteins / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D015800:Protozoan Proteins / Q000235:genetics / Q000378:metabolism*; D016808:Tetrahymena thermophila / Q000737:chemistry / Q000235:genetics* / Q000502:physiology
chemical_list: D018840:HSP70 Heat-Shock Proteins; D015800:Protozoan Proteins
keywords: Fertilization; macronuclear development; programmed nuclear death; pronuclear fusion