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Dryad

Mesodinium spp transcriptomes and associated data

Lasek-Nesselquist, Erica1; Moeller, Holly2; Paight, Christopher2; Seah, Brandon3; Shaikhutdinov, Nurislam4; Swart, Estienne3; Johnson, Matthew5

Published Jun 11, 2026 on Dryad. https://doi.org/10.5061/dryad.1jwstqk4x

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Abstract

Ciliates are a plastid-less phylum of alveolates but numerous members practice various forms of kleptoplasty. Members of the Mesodinium genus span a near-complete gradient of reliance on prey plastids, from the nearly exclusively photosynthetic M. rubrum to the heterotrophic M. pulex. The more photosynthetic the Mesodinium lineage, the fewer prey it ingests, the more efficient it is at retaining kleptoplastids, the higher its photosynthetic rate, and the more complex its handling of stolen organelles. In the heterotrophic M. pulex, a diversity of prey (including cryptophyte algae and dinoflagellates) are placed inside food vacuoles and digested immediately. The mixotrophic M. chamaeleon prefers a subset of cryptophyte algae, which lose their flagella and cell wall upon ingestion but remain inside a vacuole with their endomembrane system, nucleus, and photosynthetic capability otherwise intact. M. rubrum specializes on cryptophytes from a single genus. In M. rubrum, most of the ingested cryptophyte prey (cytoplasm, plastid, mitochondria, endomembrane system) is also maintained within a vacuole, but the nucleus is removed and positioned in close association with the ciliate’s own nuclei. This transcriptionally active prey nucleus (termed “kleptokaryon”) not only regulates prey organelle metabolism, but facilitates plastid repair and replication.  We take a comparative approach to identify transcriptomic changes along this ecological gradient. We hypothesized that increasing reliance on photosynthesis would be accompanied by increased integration of ciliate and cryptophyte metabolic pathways, especially in M. rubrum where the kleptokaryon provides a proximal source of prey genetic material.