Abstract:
The plant hormone auxin is a versatile endogenous signal influencing virtually all aspects of plant life. Nuclear, transcriptional auxin signalling involves the TIR1/AFB auxin receptors, Aux/IAA transcriptional repressors, and ARF transcription factors. TIR1/AFBs are part of the ubiquitin ligase complex, mediating the ubiquitination and degradation of Aux/IAAs and thereby releasing ARFs from their inhibition. The unexpected identification of adenylate cyclase enzymatic activity in TIR1/AFB receptors (Qi et al., 2022) and the crucial importance of its product, cAMP, for the downstream regulation of transcription (Chen et al., 2025) revise this canonical model, which has withstood the test of time for 20 years.
The major open questions relate to the target and roles of the cAMP within auxin signalling mechanism and whether similar cAMP roles can be found in context of other signalling mechanisms.
I will present novel insights into these questions and provide other mechanistic updates on cAMP-mediated signalling and show how these insights may serve as a blueprint for gaining a new understanding of other signalling pathways in plants.

Bio:
Jiří Friml studied chemistry in Brno, Czechia, earning a Ph.D. in Biochemistry (2002) and a Ph.D. in Biology (2000) from the University of Köln, Germany. As the PI of an independent group, he obtained his habilitation in Genetics (2005) from the University of Tübingen, Germany. After serving as Professor of Plant Systems Biology at the Flanders Institute of Biotechnology in Ghent, Belgium, he has been a Full Professor at the Institute of Science and Technology Austria (ISTA) since 2012.
He has made seminal contributions to fields of phytohormone transport and signalling, endocytosis, cell polarity, and the role of second messengers in plants. Author of about 380 papers in international journals, he is among the world’s most cited plant biologists. His research has been recognized with numerous international awards, including the Körber European Science Award, the EMBO Gold Medal, and the Wittgenstein Award.