Nucleic acid molecule encoding a cytochrome P450 hydroxylase in brassinosteroid biosynthesis in plants

The present invention provides a nucleic acid molecule encoding a dark-inducible cytochrome P450 hydroxylase that catalyzes the brassinosteroid biosynthesis through C-2 hydroxylations in plants. The invention also describes the methods and processes for generating expression cassettes and plasmids and for the use of these expression cassettes and plasmids to synthesize the cytochrome P450 hydroxylase or biologically active fragments of such an enzyme. The invention can be utilized to improve or decrease the stem growth of transgenic plants containing the nucleic acid molecule so that they exhibit improved growth rate and resistance to environmental stress and to identify other proteins involved in the brassinosteroid biosynthesis and in the plant growth regulation.