Growth or immune response? Higher organisms must constantly balance these two priorities. As in humans, hormones regulate this balance in plants. Researchers at the Technical University of Munich (TUM) have discovered a mechanism by which plant steroid hormones can inhibit immune responses and thereby make resources available for growth.
When plants are exposed to pathogens, they activate their immune system and simultaneously stop growing. For crop production, this results in lower yields. This interplay is important for breeding disease-resistant varieties. "Plant breeders are trying to develop varieties that can effectively ward off pathogens without reducing their yield potential. In doing so, however, they encounter biological limits: increased immunity often comes at the expense of growth," explains Brigitte Poppenberger, professor of biotechnology of horticultural crops at TUM.
Together with her team, she discovered a mechanism that could help push these biological limits: Plant steroid hormones regulate a molecular switch that controls the immune response. The work is published in the journal Proceedings of the National Academy of Sciences.
In healthy plants, steroid hormones inhibit the immune response
When plants are not challenged by pathogens, they repress their immune responses to invest all their resources in growth. Steroid hormones play a role in this process by keeping inactive the immune receptors needed to trigger an immune reaction. They do this through transcription factors—proteins that bind to DNA and influence how genetic information is processed. These factors alter the structure of immune receptors and keep them inactive until they are needed. The plant can then use resources to grow.
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