Functions in abscisic acid (ABA) signaling downstream of BZIP23. Acts as antagonistic and negative regulator of brassinosteroid (BR) signaling. Binds to BAK1 and inhibits its interaction with the BR receptor BRI1. Inhibits the formation and subsequent activation of the BRI1-BAK1 receptor complex. Interacts with BAK1. Expressed in roots, leaf blades and leaf sheaths. Expressed at low levels in stems and spikelets. Induced by abscisic acid (ABA). Phosphorylated by BRI1. Phosphorylation reduces the binding affinity to BAK1. Plants over-expressing REM4.1 are dwarf, with dark-green, short and wide flat leaf blades, short panicles, spikelets and grains, narrow bending angle of the lamina joint, and short leaf epidermis cells. Belongs to the remorin family.