Trade-off between growth and immunity: role of brassinosteroids

• Brassinosteroids (BR) regulate the growth-immunity trade-off in Arabidopsis.
• The co-receptor BAK1 is not rate-limiting between the BR and immune pathways.
• The BR-activated transcription factor BZR1 is a master regulator of this trade-off.
• BZR1 and HBI1 form a core transcriptional cascade and regulatory hub.
• The effects of BR on plant–pathogen interactions require further investigation.

A balance between growth and immunity exists in plants. Recently, the growth-promoting hormones brassinosteroids (BR) have emerged as crucial regulators of the growth-immunity trade-off, although the molecular mechanisms underlying this role remained unclear. New evidence obtained from the model plant Arabidopsis thaliana points at an indirect crosstalk between BR signaling and immunity, mediated by the transcription factors BZR1 and HBI1, which suppress immunity upon BR perception. The core transcriptional cascade formed by BZR1 and HBI1 seems to act as a regulatory hub on which multiple signaling inputs impinge, ensuring effective fine-tuning of the trade-off between growth and immunity in a timely and cost-efficient manner.