Grass-specific monolignol p-coumaroyl transferase involved in the biosynthesis of acylated monolignols or monolignol conjugates that serve as monomer precursors of lignin. Can synthesize sinapyl p-coumarate, p-coumaryl p-coumarate, sinapyl caffeate and p-coumaryl caffeate in vitro. Belongs to the plant acyltransferase family.