Big Roles for Small RNA

Ribonucleic acids (RNA) play an important role in the transfer of genetic information in cells. They are the messengers that relay information carried by the DNA to the protein-making molecular machineries. However, scientists recently discovered that RNAs also perform varied regulatory tasks. Short stretches of the molecule, around 18 to 26 nucleotides long, have been implicated in coordinating plant defense responses and development by controlling the fate of meristems, the plant version of stem cells. A study conducted by scientists from the Max Planck Institute for Chemical Ecology showed that small RNAs (smRNA) play a central role in coordinating the transcriptional changes in plants that occur after herbivore attack.

Using wild tobacco as a model, the researchers studied the expression of a gene coding for RNA-directed RNA polymerase (RdR1). RdR1 is necessary for producing small RNAs. Silencing the gene renders the plants highly susceptible to insect herbivores. The scientists also discovered that smRNAs coordinate phytohormone signaling, especially jasmonic acid and ethylene.

Considering the diversity of smRNA generated after herbivore attack and recent studies that show the ability of smRNA ingested to silence certain insect genes, the scientists hypothesized that smRNA may also function in  direct herbivore defense.

For more information visit http://www.mpg.de/bilderBerichteDokumente/dokumentation/pressemitteilungen/2008/
pressemitteilung200803171/index.html The article published by PNAS is available at http://www.pnas.org/cgi/content/abstract/0711363105v1