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Archive - Apr 16, 2017

Single-Celled Plankton Adjust to Stress by Editing Their RNA, Rather Than by Changing Gene Expression Levels

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.

New Method May Enable Scientists to Tap Vast Plant Pharmacopeia to Make New and More Effective Therapeutics

Cocaine, nicotine, capsaicin--these are just three familiar examples of the hundreds of thousands of small molecules (also called specialized or secondary metabolites) that plants use as chemical ammunition to protect themselves from predation. Unfortunately, identifying the networks of genes that plants use to make these biologically active compounds, which are the source of many of the drugs that people use and abuse daily, has vexed scientists for years, hindering efforts to tap this vast pharmacopeia to produce new and improved therapeutics. Now, Vanderbilt University geneticists think they have come up with an effective and powerful new way for identifying these elusive gene networks, which typically consist of a handful to dozens of different genes, that may overcome this road block. "Plants synthesize massive numbers of bioproducts that are of benefit to society. This team has revolutionized the potential to uncover these natural bioproducts and understand how they are synthesized," said Anne Sylvester, Ph.D., Program Director in the National Science Foundation's Biological Sciences Directorate, which funded the research. The revolutionary new approach is based on the well-established observation that plants produce these compounds in response to specific environmental conditions. "We hypothesized that the genes within a network that work together to make a specific compound would all respond similarly to the same environmental conditions," explained Jennifer Wisecaver, Ph.D., the post-doctoral fellow who conducted the study. To test this hypothesis, Dr.