Rapid Fire & Poster Presentation 39th Annual Lorne Genome Conference 2018

Cross-regulation between the ethylene and abscisic acid hormone signalling pathways is regulated by EDF transcription factors (#202)

Mathew G. Lewsey 1 , Joseph R Ecker 2
  1. La Trobe University, Bundoora, VIC, Australia
  2. Salk Institute for Biological Studies-HHMI, La Jolla, CA, USA

Several plant hormone signalling pathways exist to co-ordinate the diverse aspects of growth, development and defence. They are responsive to the changing internal and external conditions experienced during the lifespan of plants. Extensive cross-regulation occurs between these hormone signalling pathways, so as to generate appropriate responses. This cross-regulation frequently occurs by synergistic or antagonistic regulation of shared sets of genes, through the activity of hormone-responsive transcription factors. We have studied the transcription factors that regulate responses to the hormone ethylene. Ethylene is involved in diverse processes including fruit ripening, growth in the dark and defence. EIN3 is the primary transcription factor that regulates gene expression in response to ethylene, targeting and up-regulating hundreds of genes. We demonstrate that EIN3 induces expression of three repressive transcription factors from the EDF family. These in turn target hundreds of genes for down-regulation during the response to an ethylene stimulus. The targets of the activatory EIN3 are predominantly known ethylene response components. However, the targets of the repressive EDFs are enriched for components of other hormone signalling pathways, particularly the abscisic acid pathway. Ethylene-abscisic acid has long been known to exist, but the molecular mechanisms have not been characterised previously. Our results illustrate that the EDFs may be the mechanism by which ethylene suppresses abscisic acid signalling, and that this results in measurable effects on plant photosynthetic capacity. Moreover, we show that plant hormone signalling involves a network of responsive transcription factors acting in a co-ordinated fashion to condition the ultimate gene expression responses.