Symbiotic Interface of a cnidarian-Dinoflagellate Endosymbiosis

Informations

Funding country

France

Acronym

INSIDE

URL

-

Start date

1/1/2013

End date

-

Budget

240,000 EUR

Fundings

Abstract

Coral reefs are among the most beautiful and the most biodiverse marine ecosystems, but they are suffering massive declines due to environmental Coral reefs are among the most beautiful and the most biodiverse marine ecosystems, but they are suffering massive declines due to environmental perturbations, partly related to global climate change. Reefs are primarily built by calcifying corals belonging to Anthozoans (Cnidaria), such as sea anemones. Many Anthozoans rely on photosynthetic endosymbionts, dinoflagellates of the genus Symbiodinium, which are broadly referred to as zooxanthellae. The anthozoan-dinoflagellate partnership is centered on nutritional exchange: the dinoflagellate symbionts translocate a majority of their photosynthetically fixed carbon to the host in exchange for inorganic nitrogen, phosphorus and carbon from the host, in addition to a high light environment and refuge from herbivory. Various environmental stressors, such as elevated temperatures associated with global climate change, induce several cellular events that ultimately lead to loss of symbionts from host tissue, a phenomenon called “bleaching”. Bleaching can have a large variety of negative consequences specific to corals (mass mortality) as well as many that impact the reef ecosystem as a whole. Symbiosis maintenance is therefore central to coral health. Insights into the physiological mechanisms that underlie healthy as well as stressed (or bleached) anthozoans are thus critical to predict whether corals will be able to adapt to and survive climate change. Anthozoans harbour their unicellular symbionts intracellularly in vacuoles (symbiosomes) within cells in the inner or gastrodermal tissue layer. The establishment and maintenance of the symbiotic partnership must therefore be dependent on intimate molecular communications between the partners, including recognition and tolerance of symbionts, as well as adaptations for mutual transport and exchange of nutritional resources. Several genomic and cellular studies strongly suggest the putative role of host membrane as signalling and interacting/entry platforms for zooxanthellae. Indeed, the symbiosome membrane is originally derived from host plasma membranes during phagocytosis of zooxanthellae. However, its molecular components and functions are not well established. Previous results identified several proteins (Sym32, NPC1 and NPC2-D) that putatively maintain the interaction in the sea anemone Anemonia viridis. The aim of the inSIDE project is therefore to contribute to better understand the biology of symbiotic Anthozoans by focusing on the characterization of the symbiotic interface to appreciate its role in the symbiotic interaction. Our main objectives are to i) demonstrate the involvement of Sym32, NPC1 and NPC2-D in the interaction (localization and regulation), ii) fully characterize the host symbiotic membrane (symbiosome) proteome, and ii) identify new mediators of this interaction (lipids and secondary metabolites).