Macronuclear changes, autophagy and transcriptional activity during pseudoencystment in Pseudourostyla levis (Ciliophora : Hypotrichida)

Abstract

Ciliates coexisting in a habitat evolve different strategies to survive during the period of unfavourable environmental conditions. In response to starvation, Pseudourostyla levis, underges a novel phenomenon of pseudoencystment, which physiologically resembles true encystment but is functionally unrelated to it. During pseudoencystment, cells become dormant and rounded but do not secrete a cyst wall. Pseudocysts revert back to active trophic state after 12 hours without reference to any change in the environment. During this transformation, changes in the cellular morphology are accompanied by nuclear changes, reduced transcriptional activity and increased autophagy. The process of pseudoencystment is a short-term survival strategy evolved by P. levis to overcome the periods of food depletion.