Brassinosteroid signaling: from receptor kinases to transcription factors

Unlike animal steroids, which rely on intracellular steroid receptors to directly alter gene activities, plant steroids use transmembrane receptor kinases to initiate a phosphorylation-mediated signaling cascade to convey their signals into the nucleus. Recent studies have begun to unravel the biochemical details of individual steps of the brassinosteroid signal transduction pathway, including ligand binding and receptor dimerization at the cell surface, signal transmission across the cell membrane, the phosphorylation of cellular targets in the cytosol, and gene regulation inside the nucleus.