Project description:Symbiodinium, the dinoflagellate photosymbiont of corals, is posited to become more susceptible to viral infections when heat-stressed. To investigate this hypothesis, we mined transcriptome data of a thermo-sensitive and a thermo-tolerant type C1 Symbiodinium population at ambient (27°C) and elevated (32°C) temperatures. We uncovered hundreds of transcripts from nucleocytoplasmic large double-stranded DNA viruses (NCLDVs) and the genome of a novel positive-sense single-stranded RNA virus (+ssRNAV). In the transcriptome of the thermo-sensitive population only, +ssRNAV transcripts had remarkable expression levels in the top 0.03% of all transcripts at 27°C, but at 32°C, expression levels of +ssRNAV transcripts decreased while expression levels of antiviral transcripts increased. In both transcriptomes, expression of NCLDV transcripts increased at 32°C, but thermal-induction of NCLDV transcripts involved in DNA manipulation was restricted to the thermo-sensitive population. Our findings reveal that viruses infecting Symbiodinium are affected by heat stress and may contribute to Symbiodinium thermal sensitivity.
