Novel molecular mechanisms of auxin action in plants

Alicja Górska (Graz, Austria): Plant hormones are signal molecules regulating plant growth and development. Auxin was the first phytohormone to be isolated, and it is likely the most studied plant growth regulator. This hormone plays essential role in virtually every aspect of plant’s life, and mediates responses to environmental stimuli. Given the broad and prominent role of auxin in regulating plant processes, tight control of auxin signaling is required for the generation of specific auxin responses. Many auxin’s effects are mediated by changes at transcriptional level via the action of auxin response factors (ARFs). ARFs are plant-specific transcription factors that bridge perception of auxin mole-cules and the respective transcriptional response. For many years AUXIN/INDOLE-3-ACETIC ACID INDUCIBLE (AUX/IAA)-dependent ARF regulation has been considered the main mecha-nism regulating ARF protein activity. However, recently two novel mechanisms have been identi-fied, including nucleo-cytoplasmic partitioning of ARF proteins, and their proteasomal degrada-tion. In this talk, I will introduce the audience to the novel mechanisms and discuss our recent re-search results indicating that HEAVY METAL ASSOCIATED PLANT PROTEINS (HIPPs) consti-tute yet another level of ARF protein regulation.