Development and Symbiosis Establishment in the Cnidarian Endosymbiosis Model Aiptasia sp.

Madeline Bucher,Iliona Wolfowicz,Annika Guse,Elizabeth A Hambleton,Philipp A Voss

doi:10.1038/srep19867

Madeline Bucher, Iliona Wolfowicz + Show 3 more

Open Access

https://doi.org/10.1038/srep19867

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Journal: Scientific Reports	Publication Date: Jan 25, 2016
Citations: 55	License type: CC BY 4.0

Affiliation: Heidelberg University, University of Porto

Abstract

Symbiosis between photosynthetic algae and heterotrophic organisms is widespread. One prominent example of high ecological relevance is the endosymbiosis between dinoflagellate algae of the genus Symbiodinium and reef-building corals, which typically acquire symbionts anew each generation during larval stages. The tropical sea anemone Aiptasia sp. is a laboratory model system for this endosymbiosis and, similar to corals, produces non-symbiotic larvae that establish symbiosis by phagocytosing Symbiodinium from the environment into the endoderm. Here we generate the first overview of Aiptasia embryogenesis and larval development and establish in situ hybridization to analyze expression patterns of key early developmental regulators. Next, we quantify morphological changes in developing larvae and find a substantial enlargement of the gastric cavity over time. Symbiont acquisition starts soon after mouth formation and symbionts occupy a major portion of the host cell in which they reside. During the first 14 days of development, infection efficiency remains constant while in contrast, localization of phagocytosed symbionts changes, indicating that the occurrence of functional phagocytosing cells may be developmentally regulated. Taken together, here we provide the essential framework to further develop Aiptasia as a model system for the analysis of symbiosis establishment in cnidarian larvae at the molecular level.

Highlights

Despite the critical importance of symbiont acquisition in coral larvae, it is not yet clear whether the larval endoderm consists of different cell types, some of which may be specialized phagocytes, and whether the occurrence of such cell types is developmentally regulated
By co-incubating larvae with a compatible Symbiodinium strain, we find that symbiont uptake starts after mouth formation and that uptake efficiency remains constant for two weeks
A prerequisite of symbiosis studies in larval stages is an initial characterization of Aiptasia embryogenesis under standard conditions, which has heretofore not been reported

Summary

Introduction

Despite the critical importance of symbiont acquisition in coral larvae, it is not yet clear whether the larval endoderm consists of different cell types, some of which may be specialized phagocytes, and whether the occurrence of such cell types is developmentally regulated. Unknown is whether and how symbiont phagocytosis alters the morphology and physiology of the host endoderm at the single-cell level and/or the broader tissue context. This lack of knowledge is largely because the systematic study of the detailed cellular and molecular events www.nature.com/scientificreports/. Most importantly, spawning can be induced efficiently in Aiptasia under laboratory conditions, providing regular access to abundant larvae for experimentation[23] Such experimentation in Aiptasia is exploitable because of the cellular and molecular resources already generated for the system, including the Aiptasia genome[24] and several transcriptomes[25,26] and corresponding transcriptomic/genomic resources for several Symbiodinium strains[27,28,29]. We provide a foundational platform for studies of the specific molecular and cellular processes of symbiont phagocytosis and other events critical to symbiosis establishment

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