International Journal of Molecular Sciences, Vol. 19 (2018), Art. No. 2675
Brassinosteroids (BRs) are a class of phytohormones, which regulate various processes
during plant life cycle. Intensive studies conducted with genetic, physiological and molecular
approaches allowed identification of various components participating in the BR signaling—from the
ligand perception, through cytoplasmic signal transduction, up to the BR-dependent gene expression,
which is regulated by transcription factors and chromatin modifying enzymes. The identification
of new components of the BR signaling is an ongoing process, however an emerging view of the
BR signalosome indicates that this process is interconnected at various stages with other metabolic
pathways. The signaling crosstalk is mediated by the BR signaling proteins, which function as
components of the transmembrane BR receptor, by a cytoplasmic kinase playing a role of the
major negative regulator of the BR signaling, and by the transcription factors, which regulate the
BR-dependent gene expression and form a complicated regulatory system. This molecular network
of interdependencies allows a balance in homeostasis of various phytohormones to be maintained.
Moreover, the components of the BR signalosome interact with factors regulating plant reactions
to environmental cues and stress conditions. This intricate network of interactions enables a rapid
adaptation of plant metabolism to constantly changing environmental conditions.