Studying modes of BES1 activity in heat stress responses of plants

• Applicant: Professorin Dr. Brigitte Poppenberger-Sieberer
• Subject Area: Plant Cell and Developmental Biology ; Plant Biochemistry and Biophysics
• Term: from 2020 to 2024
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 436926970

• Final Report Year: 2025

Final Report Abstract

Plants have developed natural mechanisms to endure brief periods of heat stress by activating the heat-shock response, a molecular pathway that is conserved across all organisms and protects cells from damage caused by proteotoxic stress. This type of stress harms proteins and can result from various factors, including high temperatures, exposure to certain toxins, ultraviolet (UV) light, or high soil salinity. A key component of the heat-shock response is the production of heat-shock proteins (HSPs), which act as molecular chaperones to prevent protein misfolding and the synthesis of these HSPs is regulated by heat shock factors (HSFs), transcription factors that are conserved across all organisms, including plants. Beyond HSFs, plants utilize other molecular mechanisms for heat stress protection, and these involve plant hormones such as the brassinosteroids (BRs). BRs are steroids that regulate plant growth and development. Discovered in the late 1970s, they were initially recognized not only for their growth-promoting properties but also for their ability to enhance heat stress resistance when applied externally and in this project molecular mechanisms underlying these protective effects were studied. Using Arabidopsis thaliana as a model system, it could be demonstrated that a BR-regulated transcription factor called BRI1-EMS-SUPPRESSOR 1 (BES1) interacts with HSFs of the HSFA1 subfamily, facilitating the expression of HSPs. It was found that increasing BES1 activity enhanced heat stress resistance, while decreasing its activity made plants more susceptible to heat stress. Additionally, it could be shown that heat stress could activate BES1 independently of BRs, but also that the heat-stress activation was further enhanced by BRs, providing an explanation for the heat stress protective effects of BRs that were first observed over four decades ago. The most central findings of this project were published in ‘The EMBO Journal‘ and summarized in a review article in ‘Journal of Experimental Botany’. They are significant not only for advancing our understanding of the heat-shock response pathway but also for their potential applications in agriculture and horticulture. Plant biostimulants containing BRs are available and can be tested for their ability to increase crop resistance to heat stress. These natural compounds are approved for organic farming and are readily applied. Alternatively, BES1 presents an interesting target for breeding programs aimed at developing heat-resistant crop varieties with more stable yields during heatwaves.

Publications

• An expanded model of heat stress signaling – how brassinosteroids take part. Invited speaker at the ‘2022 Symposium on Plant Response to Abiotic Stress and Environmental Signals’. July 27-30 2022, Beijing, China.
  Poppenberger, B.
  
• Transcription factor BES1 interacts with HSFA1 to promote heat stress resistance of plants. The EMBO Journal, 41(3).
  Albertos, Pablo; Dündar, Gönül; Schenk, Philipp; Carrera, Sergio; Cavelius, Philipp; Sieberer, Tobias & Poppenberger, Brigitte
  
• How Brassinosteroids contribute to heat stress responses of plants. Poster presentation at the ‘4th International Brassinosteroid Conference’. August 16-18 2023, Ghent, Belgium. Received best poster award
  Dündar, G. & Poppenberger, B.
  
• How the plant hormones brassinosteroids contribute to heat stress responses of plants. Poster presentation at the ‘Plant Biology 2023’. August 5-9 2023, Savannah, Georgia, USA.
  Dündar, G. & Poppenberger, B.
  
• Modes of activity of the CESTA/BEE subfamily of bHLH transcription factors in stress responses. Invited speaker at the ‘4th International Brassinosteroid Conference’. August 16-18 2023, Ghent, Belgium.
  Poppenberger, B.
  
• bHLH proteins in brassinosteroid-conferred stress responses. Invited speaker at the 40th IPG Symposium ‘Plant Hormones at the Intersection of Stress and Development’. May 21-25, 2024, Columbia, Missouri, USA.
  Poppenberger, B.
  
• Brassinosteroide - ihr Einfluss auf das Streckungswachstum und die pflanzliche Stressresistenz. Impulsvortrag (invited speaker) beim GPZ-Treffen der AG Zierpflanzenzüchtung. September 19-20 2024, Stuttgart, Germany.
  Poppenberger, B.
  
• The heat shock response in plants: new insights into modes of perception, signaling, and the contribution of hormones. Journal of Experimental Botany, 76(7), 1970-1977.
  Dündar, Gönül; Ramirez, Veronica E. & Poppenberger, Brigitte