Tetrahymena

Abstract

The Tetrahymena genus is composed of mostly free‐living ciliated protozoa that have helped researchers gain insight into fundamental problems of cell biology. As all ciliates, Tetrahymena contain separate germline and somatic nuclei known as the micronucleus and macronucleus, respectively. The macronucleus is derived from a copy of the micronucleus through a process that involves extensive whole‐genome rearrangement and that is under intensive study. Tetrahymena thermophila can be readily manipulated using the tools of genetics, molecular biology, cell biology and biochemistry. Recently, next‐generation, whole‐genome sequencing has made possible the identification of previously unidentified genes responsible for a rich gallery of mutant phenotypes. Notable discoveries made using Tetrahymena include the structure of telomeres and telomerase, self‐splicing RNA, the first microtubular motor, and the link between histone acetylation and gene regulation. The approximately 104 Megabase macronuclear genome of T. thermophila has been sequenced and annotated; the micronuclear genome has been sequenced as well. Key Concepts Tetrahymena are large, complex eukaryotic cells well‐suited both for university research and for the undergraduate teaching‐laboratory. Tetrahymena, have been studied for nearly a century and have been the source of numerous ground‐breaking discoveries. Applying modern tools of genomics, proteomics, and next‐generation, whole‐genome sequencing has ushered in a new era of research to such topics as the assembly of basal bodies and cilia, pattern formation, novel roles for small ribonucleic acids ( RNAs ), membrane trafficking, secretion, phagocytosis, pinocytosis, cytoskeletal motility and chromosome dynamics including studies on the origins of deoxyribonucleic acid ( DNA ) replication, telomere synthesis, meiosis, recombination, apoptosis and the regulation of gene expression through epigenetic chromatin marking. Tetrahymena offer special insights into cell biological processes due to their many original and extraordinary capabilities including the use of a unique genetic code, novel twists on metabolism and protein trafficking, self‐splicing RNA, programmed genome rearrangement involved in genome surveillance, cortical patterning and cellular regeneration. Tetrahymena exhibit both conserved and evolutionarily divergent solutions to fundamental cell biological problems.