Insights into viral community composition of the cnidarian model metaorganism Aiptasia using RNA-Seq data

Abstract

Current research posits that all multicellular organisms live in symbioses with associated microorganisms and form so-called metaorganisms or holobionts. Cnidarian metaorganisms are of specific interest given that stony corals provide the foundation of the globally threatened coral reef ecosystems and their well-being strongly relies on forming mutualistic relationships with endosymbiotic algae of the genus Symbiodinium. So far, only few studies characterized viral diversity and the potential underlying functional importance to coral holobionts. Here we analyzed an existing RNA-Seq dataset of the coral model metaorganism Aiptasia CC7 (sensu Exaiptasia pallida) associated with aposymbiotic, partially populated, and fully symbiotic anemones with Symbiodinium to gain further insight into viral community composition and the relation to the algal endosymbiosis. Our approach included the selective removal of anemone host and algal endosymbiont sequences and subsequent microbial sequence annotation. Of a total of 297 million raw sequence reads, 8.6 million (~ 3%) remained after host and endosymbiont sequence removal. Of these, 3,293 sequences (paired-end read pairs) could be assigned as of viral origin. Taxonomic annotation shows that Aiptasia is associated with a diverse viral community consisting of 116 viral taxa covering 40 families. The viral community was dominated by viruses from the families Herpesviridae (12.00%), Partitiviridae (9.93%), and Picornaviridae (9.87%). Despite an overall stable viral community, we found that some viral taxa significantly changed in relative abundance when Aiptasia engage in a symbiotic relationship with Symbiodinium. Elucidation of viral taxa consistently present in all samples revealed an Aiptasia core virome of 15 viral taxa from 11 viral families that was comprised of many viruses previously reported in coral viromes. Our study provides a first insight into the viral community of Aiptasia. Aiptasia seem to harbor a diverse and overall stable viral community, although certain members change in abundance when the anemone host associates with its algal endosymbiont. However, the functional significance of this remains to be determined. , 2014;Weynberg et al., 2015 Weynberg et al., , 2017 Correa et al., 2016; Levin et al., 2016; 67 Brüwer et al., 2017; Vega Thurber et al., 2017). 6869 Unfortunately, corals are under increasing threat from anthropogenic influences, in particular 70 climate change (Hoegh-Guldberg, 1999; Hughes et al., 2003 Hughes et al., , 2017 IPCC, 2014), and 71 understanding coral metaorganisms is critical in order to mitigate strategies to conserve coral 72 reef ecosystems. To this end, the sea anemone Aiptasia (sensu Exaiptasia pallida) is becoming a 73 popular model system to investigate the coral-dinoflagellate symbiosis (Weis et al., 2008; 74 Voolstra, 2013;Baumgarten et al., 2015). While some studies looked into the association of 109 fully symbiotic anemones, animals were kept in autoclaved and sterile-filtered artificial 110 seawater (AFSW; other c...

Upside-Down but Headed in the Right Direction: Review of the Highly Versatile Cassiopea xamachana System

“…There is increasing recognition for biological and ecological importance of viruses in marine samples (Bosch et al, 2015;Thurber et al, 2017), and their role in evolution (Grasis et al, 2014). Preliminary data from the anthozoan Exaiptasia, has identified several RNA viruses, including those from Partitiviridae and Picornaviridae (Brüwer and Voolstra, 2017). The potential medical relevance, complex life strategies, as well as their host range and evolutionary history, the possible presence of RNA viruses associated with the jellyfish is of great interest to the field (Johnson, 2015;Koonin et al, 2015), and future studies should shed light on the yet-to-be explored evolutionary path of virus-cnidarian co-evolution.…”