The present invention provides a cytochrome P450-encoding gene, DAS5, as
well as an altered gene, das5-D, which are involved in the synthesis of
the plant steroid hormone brassinolide. The das5-D mutant has an insertion
of a T-DNA containing transcriptional enhancers into its promoter region.
Overexpression of the mutant thus produces large amounts of DAS5
transcript. The expression of this das5-D mutation or overexpression of
the DAS5 gene in transgenic plants causes such plants to become
significantly larger and more robust than their wild-type counterparts,
thus increasing plant yields.
