G-Quadruplex Structures as Epigenetic Regulatory Elements in Priming of Defense Genes upon Short-Term Trichoderma atroviride Inoculation in Maize

Abstract

Symbiosis establishment between Trichoderma atroviride and plant roots triggers thepriming of defense responses, among other effects. Currently, there is no clear evidence regardingthe molecular mechanisms that allow the plant to remain alert to future stimulus, either bypathogen attack or any other abiotic stress. Epigenetic modifications have emerged as a strategyto explain the increased defense response of plants in a priming state conferred by Trichoderma.Recently, various non-canonical structures of nucleic acids, especially G-quadruplex structures (G-quadruplexes or G4s), have been identified as potential targets during the establishment ormaintenance of plant signals. In the present study, we developed a screening test for theidentification of putative G4-forming sequences (PQSs) in previously identified Z. mays priminggenes. Bioinformatic analysis revealed the presence of PQSs in the promoter region of fiveessential genes playing a critical role in priming in maize. Biophysical and spectroscopy studiesshowed the formation of G4s by these PQSs in vitro, and ChIP assays demonstrate their formationin vivo. Therefore, G4 formation could play a role as an epigenetic regulatory mechanism involvedin the long-lasting primed state in maize plants.