Control of specific gene expression by gibberellin and brassinosteroid

We identified a recessive, brassinolide-insensitive mutant caused by a dele tion allele (bri1-201) of the brassinosteroid (BR) receptor BRI1. The bri1- 201 mutant displayed altered expression levels of genes differentially regu lated by gibberellin (GA). RNA-blot analysis revealed that BR and GA antago nistically regulate the accumulation of mRNAs of the GA-responsive GASA1 ge ne, as well as the GA-repressible GA5 gene. Expression studies with cyclohe ximide indicated that the antagonistic effects of GA and BR on GA5 require de novo protein synthesis. Reporter transgene analyses and RNA-blot analysi s showed that BR and GA modulate GA5 expression, at least in part, at the t ranscriptional level, and that the signals are independent and subtractive.