Brassinosteroids (BRs) are essential for various aspects of plant development. Cellular BR homeostasis is critical for proper growth and development of plants; however, its regulatory mechanism remains largely unknown. BAT1 (BR-related AcylTransferase1), a gene encoding a putative acyltransferase, was found to be involved in vascular bundle development in our full-length cDNA overexpressor (FOX) screen. Overexpression of BAT1 rendered typical BR-deficient phenotypes, which could be rescued by exogenously applied castasterone and brassinolide. Analyses of BR profiles demonstrated that BAT1 alters levels of several brassinolide biosynthetic intermediates including 6-deoxotyphasterol, typhasterol, and 6-deoxocastasterone. BAT1 is mainly localized in the endoplasmic reticulum. BAT1 is highly expressed in young tissues and vascular bundles, and its expression is induced by auxin. These data suggest that BAT1 is involved in BR homeostasis, probably by conversion of brassinolide intermediates into acylated-BR conjugates.
© 2012 The Authors. The Plant Journal © 2012 Blackwell Publishing Ltd