- In a screen for potential mediators of brassinosteroid (BR) effects, the EXORDIUM (EXO) protein was identified as a regulator of BR-responsive genes. The EXO gene was characterized as a BR-up-regulated gene. EXO overexpression under the control of the 35SCaMV promoter resulted in increased transcript levels of the BR-up-regulated KCS1, Exp5, delta-TIP, and AGP4 genes, which likely are involved in the mediation of BR-promoted growth. 35S::EXO lines grown in soil or in synthetic medium showed increased vegetative growth in comparison to wild-type plants, resembling the growth phenotype of BR-treated plants. Thus, the EXO protein most likely promotes growth via the modulation of gene expression patterns. (C) 2004 Federation of European Biochemical Societies. Published by Elsevier B.V. All rights reserved
