Recent Advances in Ciliate Biology

Abstract

Ciliates are a diverse group of unicellular eukaryotes that vary widely in size, shape, body plan, and ecological niche. Here, we review recent research advances achieved with ciliate models. Studies on patterning and regeneration have been revived in the giant ciliate Stentor, facilitated by modern omics methods. Cryo-electron microscopy and tomography have revolutionized the structural study of complex macromolecules such as telomerase, ribozymes, and axonemes. DNA elimination, gene scrambling, and mating type determination have been deciphered, revealing interesting adaptations of processes that have parallels in other kingdoms of life. Studies of common eukaryotic processes, such as intracellular trafficking, meiosis, and histone modification, reveal conservation as well as unique adaptations in these organisms that are evolutionarily distant from other models. Continual improvement of genetic and molecular tools makes ciliates accessible models for all levels of education and research. Such advances open new avenues of research and highlight the importance of ciliate research. Expected final online publication date for the Annual Review of Cell and Developmental Biology Volume 38 is October 2022. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

A Review for the Special Issue on Paramecium as a Modern Model Organism

“…Returning briefly to the behavior of the P. bursaria with and without Chlorella endosymbionts, we see that the cells' reaction of an AR and an action potential, which is to a step up in light and transient depolarization, keeps these cells in the shade by a klino-kinesis mechanism [41]. Likewise, when cells with Chlorella experience a step down to lower light, they have an AR that can send them back into the lighted area.…”

“…These P. bursaria can be studied with or without the Chlorella, setting up an interesting comparison and control. Iwatsuki and Naitoh [41] showed that P. bursaria are intrinsically photosensitive, even without symbionts like Chorella that are photosynthetic. They point out that Chlorella symbionts alter the intrinsic responses of P. bursaria to changes in light; Without Chlorella, P. bursaria react to the step up in light with an avoiding reaction (AR) and transient depolarization, which help to keep the cells in the shade and out of harmful radiation.…”

“…Upon stimulation of the posterior, they zoom away from predators [39,40]. Paramecium swims against water currents (rheotaxis) and avoids bright light [41] and extremes of temperature. These cells typically swim in helical paths interrupted by abrupt spontaneous changes in direction that Jennings named avoiding reactions.…”

SMORES: A Simple Microfluidic Operating Room for the Examination and Surgery ofStentor coeruleus

“…Ciliates, including Tetrahymena and Paramecium, are powerful unicellular model organisms that have been used to uncover fundamental insights in diverse biological processes from DNA replication to the microtubule cytoskeleton [1][2][3] . Recently, the ciliate Stentor coeruleus has received renewed interest as a model for studying wound healing, regeneration, habituation and learning in a unicellular system [4][5][6][7] .…”

SMORES: a simple microfluidic operating room for the examination and surgery of Stentor coeruleus

“…Ciliates, including Tetrahymena and Paramecium , are powerful unicellular model organisms that have been used to uncover fundamental insights in diverse biological processes from DNA replication to the microtubule cytoskeleton 1 – 3 . Recently, the ciliate Stentor coeruleus has received renewed interest as a model for studying wound healing, regeneration, habituation and learning in a unicellular system 4 – 7 .…”