Restoration of cellular integrity following “ballistic” pronuclear exchange during Tetrahymena conjugation

Developmental biology

Eric S. Cole^1¹  Oleksandr Dmytrenko^1² 

[1]Biology Department, St. Olaf College, Northfield, MN, USA^1

[2]The Boulder Laboratory for 3D Electron Microscopy of Cells, Department of Molecular, Cellular, and Developmental Biology, University of Colorado, Boulder, CO, USA^2

关键词: Ciliates;    Conjugation;    Fertilization;    Gametes;    Membrane fusion;    Plasma membrane, Tetrahymena;   

DOI  :  10.1016/j.ydbio.2018.09.019

学科分类：生物科学（综合）

来源: Academic Press

【 摘 要 】

During sexual reproduction or conjugation, ciliates form a specialized cell adhesion zone for the purpose of exchanging gametic pronuclei. Hundreds of individual membrane fusion events transform the adhesion zone into a perforated membrane curtain, the mating junction. Pronuclei from each mating partner are propelled through this fenestrated membrane junction by a web of short, cris-crossing microtubules. Pronuclear passage results in the formation of two breaches in the membrane junction. Following pronuclear exchange and karyogamy (fertilization), cells seal these twin membrane breaches thereby re-establishing cellular independence. This would seem like a straightforward problem: simply grow membrane in from the edges of each breach in a fashion similar to how animal cells “grow” their cytokinetic furrows or how plant cells construct a cell wall during mitosis. Serial section electron microscopy and 3-D electron tomography reveal that the actual mechanism is less straightforward. Each of the two membrane breaches transforms into a bowed membrane assembly platform. The resulting membrane protrusions continue to grow into the cytoplasm of the mating partner, traverse the cytoplasm in anti-parallel directions and make contact with the plasma membrane that flanks the mating junction. This investigation reveals the details of a novel, developmentally-induced mechanism of membrane disruption and restoration associated with pronuclear exchange and fertilization in the ciliate, Tetrahymena thermophila.

【 授权许可】

CC BY