Transcriptomic responses of free-living Chroomonas sp. Dc01 and that ingested by Nusuttodinium aeruginosum upon illumination

Endosymbiosis of unicellular eukaryotic algae into previously nonphotosynthetic eukaryotes has established chloroplasts in several eukaryotic lineages. Additionally, certain unicellular organisms in several different lineages ingest algae and utilize them as temporal chloroplasts (kleptoplasts) for weeks to months before digesting them. Among these organisms, the dinoflagellate Nusuttodinium aeruginosum ingests the cryptomonad Chroomonas sp. and enlarges the kleptoplast with the aid of the cryptomonad nucleus. In order to understand how free-living Chroomonas sp. Dc01 responds to the light illumination and to compare transcriptomic responses of free-living Chroomonas sp. Dc01 with those of Chroomonas sp. ingested by Nusuttodinium aeruginosum, we examined and compared the transcriptomic changes of free and ingested Chroomonas sp. (5 days after ingestion by N. aeruginosum) following illumination. Cells were precultured in the dark for 24 h, illuminated for 12 h, and again returned to the dark. The nuclear transcriptome of free and ingested Chroomonas sp. was examined at hours 0 (just before illumination), 1, 6, 12 (during illumination), and 13 (1 h after the transfer to the dark)