Single-celled plankton known as dinoflagellates have now been shown to cope with stress by using an unexpected strategy of editing their RNA rather than changing gene expression levels. The finding by KAUST (King Abdullah University of Science and Technology) researchers in Saudi Arabia began when a team led by Associate Professor Christian Voolstra and Assistant Professor Manuel Aranda compared RNA transcripts from two strains of dinoflagellates thought to belong to the same species in the genus Symbiodinium. The transcripts had more differences than expected, indicating a more distant relationship. However, the team speculated that the RNA transcripts might instead have been edited, producing different information than that encoded in the cell’s DNA. RNA editing had previously been observed in the mitochondria and plastids of dinoflagellates, but not in genes encoded in the nucleus. Earlier studies by Dr. Voolstra and Dr. Aranda had shown that gene expression changes very little in dinoflagellates under stressful conditions. The researchers wondered: “What if they do it completely differently? What if they just edit transcripts the way they need instead of changing expression?’” recalled Dr. Aranda. To test this hypothesis, the team analyzed transcriptomes from Symbiodinium cultures grown in normal conditions and stressed by cold, heat, or darkness. A conservative estimate uncovered 3,300 RNA edits. “This expands the encoding capacity beyond what’s in the genome,” says Dr. Aranda, effectively giving the cell a “fuzzy genome.” “Instead of having just one version of a protein, they can produce multiple different versions by changing the message on a different level.” The team then turned its attention to 229 genes edited in all four growth conditions.
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