Ribosomal DNA (rDNA) sequences are essential parts of many species’ genomes. The highly repetitive nature of these DNA sequences makes them susceptible to shrinkage over time—and if they shrink too much, cells die. If rDNA shrinks too much in germ cells, the cells that become eggs and sperm, then individuals may become infertile and their lineages may go extinct. Researchers have suspected that something helps to keep our rDNA intact over the generations—and so keep humans and other species fertile—but they did not know what it was. New research from Whitehead Institute Member Yukiko Yamashita and postdoc Jonathan Nelson reveals rDNA’s unlikely protector: a retrotransposon, a genetic element that had been thought of as a genetic parasite because it seems to exist only to replicate itself. Their research, published in the journal PNAS on May 30, 2023, explains how this so-called parasite actually plays an essential role in maintaining rDNA and preserving fertility through the generations.
