Reciprocal effects of programmed cell death on fitness in unicellular endosymbiotic chlorella and its ciliate host

This uploaded content contains the data and R script information used to generate the figures for the following manuscript: Title: Reciprocal effects of programmed cell death on fitness in unicellular endosymbiotic chlorella and its ciliate host Authors: Santosh Sathe and Lutz Becks Affiliation: Aquatic Ecology and Evolution, Department of Biology, University of Konstanz, 78464 Konstanz, Germany Contact: Santosh Sathe ([e-mail]) A brief summary of the work: The adaptive significance of programmed cell death (PCD), an active form of cellular suicide, is well understood in multicellular organisms, yet its evolutionary origins and function in unicellular life remain unresolved. In this study, we present experimental evidence that the unicellular endosymbiotic alga Chlorella variabilis and its ciliate host Paramecium bursaria both undergo PCD and this form of cell death is beneficial to their clonal populations and their endosymbiotic partners. Additionally, PCD in C. variabilis has detrimental effects on its predatory host, Paramecium duboscqui, while necrotic cell death generally proves harmful across the system. These results support the idea that PCD evolved as an adaptive trait early in endosymbiotic evolution, facilitating the development of mutualistic interactions between hosts and symbionts. Altogether, our findings deepen the understanding of PCD's functional role in unicellular organisms and its contribution to endosymbiosis evolution.