Regulated development of cannibalistic supergiant cells

Abstract

Virtually all paradigms in developmental biology apply to differentiating cells and tissues within multicellular animals and plants. However, unicellular eukaryotes, which must simultaneously perform all roles necessary for organismal function, also form complex and specialized structures, using processes that take place exclusively within the confines of a single cell. Here, we describe a ciliate (Euplotes gigatrox sp. nov.) undergoing drastic morphological transformations within a genetically uniform population, the most spectacular being the appearance of "supergiants" that increase in size, change shape, and modify their locomotion and feeding behaviour to cannibalize clonal relatives. We explore supergiant formation from the perspective of life cycle, ecological strategy, and gene expression, demonstrating that supergiants are distinct, regulated, transcriptionally unique stages. These reversibly differentiated cells require both external and internal triggers to develop and have evolved regulatory loops to ensure coupling between environmental and physiological conditions. This system provides a blueprint for approaching both cell differentiation and functional ecology in unicellular organisms, which might open new avenues for the generalization and contextualization of known morphogenetic mechanisms, as well as the discovery of new ones.