Brassinosteroids (BR) acyltransferase with acyl-CoA ligase activity toward brassinolide (BL), castasterone (CS), typhasterol (TY), 6-deoxotyphasterol (6-deoxoTY), and 6-deoxocastasterone (6-deoxoCS) and thus converts them to corresponding lauroyl esters (PubMed:23071642, PubMed:23204503, PubMed:23020607). Regulates BR homeostasis and promotes BR-mediated cell growth regulation (PubMed:23071642, PubMed:23204503). Involved in vascular bundle development (PubMed:23020607). Plant hormone biosynthesis; brassinosteroid biosynthesis. Localizes in the endoplasmic reticulum in young tissues and the phloem of vascular bundles. Highly expressed in young tissues and vascular bundles (PubMed:23020607). Mostly expressed in young leaves, primary roots, flowers (including petals and sepals), and siliques (PubMed:23204503). In young seedlings, mainly observed in the vascular cylinder of cotyledons, leaves and hypocotyls. Accumulates also in root tips, lateral root initiation sites and the maturation zone of the primary root. In adult plants, present in the vasculature of the inflorescence stems, especially in phloem cells. Induced by 24-epi-brassinolide (24-epiBL, eBL) and inhibited by abscisic acid (ABA) (PubMed:23204503). Stimulated by auxin (PubMed:23020607). No obvious growth phenotype under standard growth conditions (PubMed:23071642, PubMed:23204503). The bat1-1 mutant exhibits longer stems before flowering, but reaches normal height after flowering, with larger inflorescence stems containing an increased number of vascular bundles (PubMed:23020607). Belongs to the plant acyltransferase family.