|Institution||University of California, Santa Cruz|
The diversity and function of viruses in coral holobionts has received only recent attention. The non-reef building gorgonian octocoral, Gorgonia ventalina, is a major constituent of Caribbean reefs, and is impacted by outbreaks of the putatively fungal disease aspergillosis. We investigated viral communities associated with G. ventalina healthy and diseased tissues to understand their potential role in the ecology of the holobiont and dynamics in aspergillosis. Pyrosequencing was used to prepare a total of 514,632 sequence reads of DNA- and RNA-based community viral genomes (metaviromes). RNA viral assemblages were comprised of primarily unidentifiable reads, with most matching host expressed sequence tags and other RNA virus metaviromes. DNA metaviromes were comprised of contiguous sequences (contigs) that matched primarily metazoan and bacterial proteins. Only ~5% of contigs matched viral proteins which were primarily cyanophage and viruses of Chlorella and Ostreococcus. Healthy and diseased metavirome contigs shared a large proportion of total sequence identity, however only 1 of 7 healthy and diseased contigs > 5 Kbp was present in both libraries. One contiguous sequence unique to the diseased metavirome recruited almost 31 % of all reads in the library and was selected for post-genomic verificiation of abundance by quantitative PCR. This contig was detected by quantitative PCR only in the diseased viral preparations used to generate metaviromes. However, it was not detected in another 6 healthy nor 6 diseased DNA extracts, nor as transcripts via quantitative reverse-transcriptase PCR, so we ruled out the likelihood it was associated with pathogenesis. Our results confirm that DNA and RNA viruses comprise a component of the gorgonian holobiont, suggesting that they may play a role in the ecology of G. ventalina. We speculate that the detected viral genotypes may play a role in regulating the abundance of bacteria that opportunistically colonize diseased G. venatlina tissues.