Researchers discover beneficial jumping gene
“Silencing of transposon activity is a complex process that is based on the interplay between different types of epigenetic signals,” Eulgem continued. “Typically H3K9me2 is of critical importance for transposon silencing. However, we found H3K9me2 is not important for COPIA-R7 silencing, perhaps because this type of epigenetic signal has acquired a different function within the RPP7 gene. While we found H3K9me2 to promote RPP7 activity, it seems to have lost its function for COPIA-R7 silencing.”
Arabidopsis plants use H3K9me2-mediated messenger RNA processing to accurately set RPP7 activity to precisely defined levels. In principle, scientists interested in crop improvement can now use the UCR discovery to design new types of molecular switches based on H3K9me2-mediated messenger RNA processing. Using standard molecular biological methods, transposon sequences that are naturally associated with this epigenetic signal can be inserted into suitable genes and thereby alter the activity levels of these genes.
“Our results are critical for the basic understanding of how transposons can affect the evolution of their hosts — something not well understood at this time,” said Tokuji Tsuchiya, the first author of the research paper and an assistant specialist in Eulgem’s lab. “Besides this impact on basic research, the epigenetic mechanism we discovered can possibly be utilized for biotechnological crop improvement. In principle, the switch mechanism we discovered can be applied to all crop species that can be genetically modified.”
Next, Eulgem plans to expand his lab’s research to how plants use the modulation of H3K9me2 levels at COPIA-R7 to dynamically adjust RPP7 activity when they are attacked by a pathogenic microorganism and to explore if this mechanism also applies to additional genes.
“It would make sense to assume that at other transposons, H3K9me2 levels are also modulated during immune responses and that this epigenetic mark affects the activity of other genes that are important for plant immunity,” Eulgem said. “If this is true, we have uncovered a completely new genetic — or epigenetic — mechanism that allows plants to sense that they are under pathogen attack and to initiate appropriate immune responses.”
The research was funded by three grants to Eulgem from the National Science Foundation.