The host transcriptome remains unaltered during the establishment of coral–algal symbioses

Abstract

Coral reefs are based on the symbiotic relationship between corals and photosynthetic dinoflagellates of the genus Symbiodinium. We followed gene expression of coral larvae of Acropora palmata and Montastraea faveolata after exposure to Symbiodinium strains that differed in their ability to establish symbioses. We show that the coral host transcriptome remains almost unchanged during infection by competent symbionts, but is massively altered by symbionts that fail to establish symbioses. Our data suggest that successful coral-algal symbioses depend mainly on the symbionts' ability to enter the host in a stealth manner rather than a more active response from the coral host.

Marine Invertebrate Larvae Associated with Symbiodinium: A Mutualism from the Start?

“…The genomes for types within clades A, B, and F (Shoguchi et al, 2013;Lin et al, 2015;Aranda et al, 2016), transcriptomes for types within clades A-D (Bayer et al, 2012;Ladner et al, 2012;Parkinson et al, 2016) and the plastid genome for type B1 (Mungpakdee et al, 2014) and type C3 have been sequenced in recent years, but further information, especially on metabolic pathways, is still missing. However, a few experiments investigated differential gene expression in coral larvae with and without symbionts, all of which reported the absence of or rather small gene expression differences in the transcriptomes of symbiotic hosts when compared to the aposymbiotic state (deBoer et al, 2007;Voolstra et al, 2009b;Schnitzler and Weis, 2010). Only recently, a study by Mohamed et al (2016) detected a transient period of differential expression involving a limited number of genes (3% of assayed transcriptome) 4 h after the exposure of Acropora digitifera planula larvae to a competent strain of Symbiodinium.…”

“…In the case of cnidarians, while broad knowledge on their association with Symbiodinium is available, there are still relatively few studies on the larva-Symbiodinium association (Rodriguez-Lanetty et al, 2006;Voolstra et al, 2009b;Schnitzler and Weis, 2010;Wolfowicz et al, 2016). Approximately 80-90% of reef-building coral species (Scleractinia) are broadcast spawners and acquire symbionts horizontally (Harrison and Wallace, 1990;Baird et al, 2009;Harrison, 2011).…”

Do reef corals age?

“…These include the establishment of associations with endosymbiotic algae (where transmission is horizontal and not via the parent) (Little, van Oppen & Willis, 2004;Voolstra et al, 2009) and micro-organisms (Sharp et al, 2010;Apprill et al, 2012;Sharp, Distel & Paul, 2012), and the development of immunity and allorecognition systems (Frank et al, 1997;Nozawa & Loya, 2005;Puill-Stephan et al, 2012). Physiological changes continue to be made as corals develop from juveniles to adults and through adulthood with the following examples relating to both ramets and genets, depending on the study.…”

Host hybridization alters specificity of cnidarian–dinoflagellate associations

“…temperature and/or light regimes) for either the coral host or the dinoflagellate endosymbiont. In hostsymbiont combinations that fail to form sustained symbioses, postphagocytic winnowing involves host cell apoptosis, proteolysis and immune system responses (Dunn & Weis 2009, Voolstra et al 2009). In contrast, there are minimal to relatively minor postphagocytic changes in host gene expression of pairings that lead to a successful symbiosis, suggesting that Symbiodinium inhabit their hosts by either escaping detection or active inhibition of the host response (Barneah et al 2006, Rodriguez-Lanetty et al 2006b, Voolstra et al 2009).…”

“…In hostsymbiont combinations that fail to form sustained symbioses, postphagocytic winnowing involves host cell apoptosis, proteolysis and immune system responses (Dunn & Weis 2009, Voolstra et al 2009). In contrast, there are minimal to relatively minor postphagocytic changes in host gene expression of pairings that lead to a successful symbiosis, suggesting that Symbiodinium inhabit their hosts by either escaping detection or active inhibition of the host response (Barneah et al 2006, Rodriguez-Lanetty et al 2006b, Voolstra et al 2009). Finally, competition within a host among competent Symbiodinium 'types' may also play a role in determining the dominant endosymbiont (Fitt 1985, Coffroth et al 2001, Little et al 2004, Thornhill et al 2006b).…”