title: Are Niemann-Pick type C proteins key players in cnidarian-dinoflagellate endosymbioses?
abstract: The symbiotic interaction between cnidarians, such as corals and sea anemones, and the unicellular algae Symbiodinium is regulated by yet poorly understood cellular mechanisms, despite the ecological importance of coral reefs. These mechanisms, including host-symbiont recognition and metabolic exchange, control symbiosis stability under normal conditions, but also lead to symbiosis breakdown (bleaching) during stress. This study describes the repertoire of the sterol-trafficking proteins Niemann-Pick type C (NPC1 and NPC2) in the symbiotic sea anemone Anemonia viridis. We found one NPC1 gene in contrast to the two genes (NPC1 and NPC1L1) present in vertebrate genomes. While only one NPC2 gene is present in many metazoans, this gene has been duplicated in cnidarians, and we detected four NPC2 genes in A. viridis. However, only one gene (AvNPC2-d) was upregulated in symbiotic relative to aposymbiotic sea anemones and displayed higher expression in the gastrodermis (symbiont-containing tissue) than in the epidermis. We performed immunolabelling experiments on tentacle cross sections and demonstrated that the AvNPC2-d protein was closely associated with symbiosomes. In addition, AvNPC1 and AvNPC2-d gene expression was strongly downregulated during stress. These data suggest that AvNPC2-d is involved in both the stability and dysfunction of cnidarian-dinoflagellate symbioses.
authors: UMR7138, Université de Nice-Sophia-Antipolis, Faculty of Science, 28 Avenue Valrose, Nice, 06108, France; Institut de Biologie Paris-Seine, UMR7138, Sorbonne Universités Paris VI, 7 quai Saint Bernard, Paris, 75005, France; Institut de Biologie Paris-Seine, UMR7138, Centre National de la Recherche Scientifique, Paris, 75016, France.
authors: Vincent
authors: V
authors: Dani
authors: Philippe
authors: P
authors: Ganot
authors: Fabrice
authors: F
authors: Priouzeau
authors: Paola
authors: P
authors: Furla
authors: Cecile
authors: C
authors: Sabourault
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D004141:Dinoflagellida; D020440:Gene Duplication; D008565:Membrane Proteins / Q000235:genetics*; D008969:Molecular Sequence Data; D010802:Phylogeny; D012615:Sea Anemones / Q000235:genetics*; D013559:Symbiosis / Q000235:genetics*
chemical_list: D008565:Membrane Proteins
keywords: NPC1; NPC2; bleaching; cnidarian-dinoflagellate interaction; sterol transport; symbiosis