Professor Technical University of Munich Freising, Bayern, Germany
Body of Abstract: Plants are highly sensitive to changes in the environment and especially temperature changes have a significant effect. While warmth can accelerate certain growth processes heat stress impairs both vegetative and reproductive development and can thereby reduce yields. To protect themselves, plants employ the heat shock response, an ancient signaling pathway that utilizes transcription factors called heat shock factors (HSFs) to activate heat stress responsive genes via binding to heat shock elements (HSE) in their promoters. More than 30 years ago it had first been discovered that the plant hormones brassinosteroids (BRs), when applied externally, could increase the survival rates of different plant species, that were exposed to heat stress; however, the molecular modes underlying this activity had remained largely elusive. Recently we and others have shed light on molecular events that contribute to this activity in Arabidopsis thaliana and these will be summarized here. The presentation will focus on the interplay of BR signaling components with the HSFs, in particular on the cooperation of the BR-regulated transcription factors BES1/BZR1 with HSFs of the HSFA1-type and how heat stress activates these proteins for stress protective reactions. In addition, we will consider recent findings of others, to present an up-dated model of BR signaling contribution to heat stress responses in plants.