|
In humans and animals, steroid hormones regulate transcription via membrane-bound receptors. These receptors have an extracellular ligand-binding domain and an intracellular domain that are responsible for transduction the signal to the next member along the signaling pathway. Brassinosteroids (BRs) are structuraliy to the animal steroid hormones found in vertebrates and insects. Plants also use steroids as signaling molecules. BRs regulate the expression of numerous genes associated with plant development, and require the activity of a serine/threonine (Ser/Thr) receptor kinase to realize these effects. Signaling in dicotyledonous (e.g., Arabidopsis thaliana) and monocotyledonous (e.g., Oryza sativa) models, is mediated by the receptor kinases BRI1 and OsBRI1, respectively. The extracellular domain of BRI1 perceives BRs, and the signal is then mediates via an intracellular kinases domain that autophosphorylates Ser and Thr residues an potentially, other substrates. BRI1 transduces steroid signals the plasma membrane and mediates genomic effects.
|