How Plants Really Respond to Heat Stress
The past few decades have seen an increased incidence of heat waves with record highs around the globe, and this is seen as a result of climate change. Heat waves have been occurring more frequently, have been hotter, and have been lasting longer with severe consequences not only for humans and animals, but also for plants.
To survive short periods of heat stress, plants activate a molecular pathway called the heat-shock response. This heat-shock response (common to all organisms) protects cells from damage inflicted by proteotoxic stress, which damages proteins. Such stress is not only caused by heat but can also result from exposure to certain toxins, UV light, or soil salinity.
The heat shock response protects cells in various ways, one of them being production of so-called heat-shock proteins, which serve as molecular shields that protect proteins by preventing misfolding.
Plants respond to heat stress by activating heat shock factors and also other molecular players. In particular, hormones as chemical messengers are involved. Among the hormones that plants produce are the brassinosteroids, which primarily regulate their growth and developments. But, in addition to their growth-promoting properties, brassinosteroids have other interesting abilities, one of them being their ability to increase the heat stress resistance of plants, and researchers at TUM have recently discovered what contributes to this protective ability.
Using the model plant Arabidopsis thaliana, a research group led by Brigitte Poppenberger, Professor for Biotechnology of Horticultural Crops, has been able to elucidate how a specific transcription factor — a special protein responsible for switching certain sections of the DNA on or off — is regulated by brassinosteroids. This transcription factor, called BES1, can interact with heat shock factors thereby allowing genetic information to be targeted towards increased synthesis of heat shock proteins. When BES1 activity is increased, plants become more resistant to heat stress, and when it is decreased, they become more sensitive to it. Furthermore, the group has demonstrated that BES1 is activated by heat stress and that this activation is stimulated by brassinosteroids.
“These results are not only of interest to biologists trying to expand our understanding of the heat shock response but also have potential for practical application in agriculture and horticulture,” Poppenberger says.
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