Molecular mechanisms underlying cross-talk phenomena in hormone-regulated plant defense responses in Arabidopsis thaliana

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Plants live in complex environments in which they have to combat a broad range of microbial pathogens. Under this selective pressure, plants have developed a highly sophisticated defense system that recognizes pathogen-associated molecules. Subsequently, appropriate defense responses are activated many of them being coordinated by the phytohormones salicylic acid (SA), jasmonic acid (JA) and ethylene (ET). While infection with biotrophic pathogens evokes SA-mediated defense responses, infection with necrotrophic pathogens elicits JA/ET-dependent responses. Both signaling pathways cross-communicate in an antagonistic manner, so that defense pathways can be prioritized upon demand. Here we aim to elucidate the molecular mechanisms underlying this cross-talk. Recently, we have presented genetic evidence that TGA transcription factors, which have been classified as essential activators of SA-mediated responses, are also required for the activation of JA- and ET-dependent defense mechanisms in Arabidopsis thaliana. This activation function seems to be negatively regulated by SA. This proposal aims to understand cross-talk mechanisms between the SA and the ET defense hormone pathways.