The Zinc Finger Protein Zfr1p Is Localized Specifically to Conjugation Junction and Required for Sexual Development in Tetrahymena thermophila

Abstract

Conjugation in Tetrahymena thermophila involves a developmental program consisting of three prezygotic nuclear divisions, pronuclear exchange and fusion, and postzygotic and exconjugant stages. The conjugation junction structure appears during the initiation of conjugation development, and disappears during the exconjugant stage. Many structural and functional proteins are involved in the establishment and maintenance of the junction structure in T. thermophila. In the present study, a zinc finger protein-encoding gene ZFR1 was found to be expressed specifically during conjugation and to localize specifically to the conjugation junction region. Truncated Zfr1p localized at the plasma membrane in ordered arrays and decorated Golgi apparatus located adjacent to basal body. The N-terminal zinc finger and C-terminal hydrophobic domains of Zfr1p were found to be required for its specific conjugation junction localization. Conjugation development of ZFR1 somatic knockout cells was aborted at the pronuclear exchange and fusion conjugation stages. Furthermore, Zfr1p was found to be important for conjugation junction stability during the prezygotic nuclear division stage. Taken together, our data reveal that Zfr1p is required for the stability and integrity of the conjugation junction structure and essential for the sexual life cycle of the Tetrahymena cell.

Role of the Cytosolic Heat Shock Protein 70 Ssa5 in the Ciliate Protozoan Tetrahymena thermophila

“…; Xu et al. ). On the other hand, the defects in Atg8 and Vps34 that play essential roles in autophagosome formation on the parental macronucleus in the early stage of PND do not affect the initiation of PND (Akematsu et al.…”

“…; Xu et al. ), are likely involved in the meshwork formation. In addition to microtubule mediated functions for nuclear movements, microtubule‐based complexes become a trigger for pronuclear membrane fusion in yeast.…”

“…; Xu et al. ) may insure survival of parental clones in the case of failure of proper gamete exchange, which enables the cells to have another chance to produce progeny by mating with other strains that can complement the defects. Once the checkpoint is passed, conjugation does not stop even though some errors occur on the already executed programs (Akematsu et al.…”

Function of the Male-Gamete-Specific Fusion Protein HAP2 in a Seven-Sexed Ciliate

“…It should also be noted that a recent screen of proteins up-regulated during conjugation in T. thermophila has led to the identification of a gene encoding a predicted zinc-finger domain containing protein ( ZFR1 ; TTHERM_01285910), which localizes to the conjugation junction of mating cells and, as with HAP2, appears necessary for normal fertility and pair-stability [26]. The possibility these and other proteins act in concert to drive membrane fusion, and perhaps pore expansion, clearly bears further investigation.…”

Micronucleus-specific histone H1 is required for micronuclear chromosome integrity in Tetrahymena thermophila

“…RT-PCR was performed with the SYBR Premix Ex TaqTM (TaKaRa) on an ABI StepOne Plus system (Applied Biosystems, USA) [ 26 ]. The following parameters were progressively used for PCR before the dissociation stage and with 17S rRNA as the internal control: 30 s at 95°C, 40 cycles of 95°C for 5 s, 60°C for 35 s. Data from the real-time PCR experiments were analyzed using the 2 −ΔΔCt method.…”