Association of coral algal symbionts with a diverse viral community responsive to heat shock

Abstract
Stony corals provide the structural foundation of coral reef ecosystems and are termed holobionts given they engage in symbioses, in particular with photosynthetic dinoflagellates of the genus Symbiodinium. Besides Symbiodinium, corals also engage with bacteria affecting metabolism, immunity, and resilience of the coral holobiont, but the role of associated viruses is largely unknown. In this regard, the increase of studies using RNA sequencing (RNA-Seq) to assess gene expression provides an opportunity to elucidate viral signatures encompassed within the data via careful delineation of sequence reads and their source of origin.Here, we re-analyzed an RNA-Seq dataset from a cultured coral symbiont (Symbiodinium microadriaticum, Clade A1) across four experimental treatments (control, cold shock, heat shock, dark shock) to characterize associated viral diversity, abundance, and gene expression. Our approach comprised the filtering and removal of host sequence reads, subsequent phylogenetic assignment of sequence reads of putative viral origin, and the assembly and analysis of differentially expressed viral genes. About 15.46% (123 million) of all sequence reads were non-host-related, of which <1% could be classified as archaea, bacteria, or virus. Of these, 18.78% were annotated as virus and comprised a diverse community consistent across experimental treatments. Further, non-host related sequence reads assembled into 56,064 contigs, including 4856 contigs of putative viral origin that featured 43 differentially expressed genes during heat shock. The differentially expressed genes included viral kinases, ubiquitin, and ankyrin repeat proteins (amongst others), which are suggested to help the virus proliferate and inhibit the algal host's antiviral response.Our results suggest that a diverse viral community is associated with coral algal endosymbionts of the genus Symbiodinium, which prompts further research on their ecological role in coral health and resilience.

Citation
Brüwer JD, Agrawal S, Liew YJ, Aranda M, Voolstra CR (2017) Association of coral algal symbionts with a diverse viral community responsive to heat shock. BMC Microbiology 17. Available: http://dx.doi.org/10.1186/s12866-017-1084-5.

Acknowledgements
Research reported in this publication was supported by a Science and Engineering Engagement and Development (SEED) fund (FCS/1/2449–01-01: The role of viruses in structuring the marine environment of the Red Sea) to the Red Sea Research Center at KAUST. JDB was funded by a Visiting Student Research Program (VSRP) fellowship by King Abdullah University of Science and Technology (KAUST). The funders had no role in the design of the study and collection, analysis, and interpretation of data, and in writing the manuscript.

Publisher
Springer Nature

Journal
BMC Microbiology

DOI
10.1186/s12866-017-1084-5

PubMed ID
28818037

Additional Links
https://bmcmicrobiol.biomedcentral.com/articles/10.1186/s12866-017-1084-5

Relations
Is Supplemented By:

Permanent link to this record