DAS5, a P450 Protein Involved in the Brassinosteroid Biosynthesis Pathway of Plants
Inventors: Joanne Chory and Zhiyong Wang
Potential Uses: Plant Biology, Agriculture, Horticulture
Genetic modifications of plants to increase the expression of DAS5 results in a variety of useful phenotypes such as increased fresh weight and increased overall plant size.
The invention provides identification of nucleic acid molecules encoding proteins involved in the synthesis of brassinosteroids in plants, methods of increasing endogenous levels of brassinosteroids, insect protection and methods of increasing biomass by modulating levels of brassinosteroid pathway components. These molecules appear to modulate brassinosteroid response pathways at the level of their biosynthetic enzymes, therefore altering brassinosteriod-related responses and signaling pathways. An altered gene, DAS5 is disclosed which is involved in the synthesis of brassinolides. The DAS5 gene encodes a member of the P450 family of proteins. The das5-D mutant was generated using an activation tagging approach. The activation tagging procedure often produces dominant mutations, whereby the gene product of the altered gene is produced at high levels. By "das5-D" is meant the DAS5 gene additionally containing upstream activation sequences which cause a high level of DAS5 transcript and, consequently, high levels of DAS5 protein production in cells containing this construct. Transgenic plants carrying this altered gene are expected to have high levels of DAS5 gene expression and high levels of active DAS5 protein compared to widltype. Both overexpression of the DAS5 gene and expression of the dominant activation-tagged das5-D mutation in this invention resulted in increased brassinosteroid levels throughout the plant and produce the das5-D mutant phenotype. For example, when das5-D was expressed in wild type Arabidopsis plants, the fresh weight increased by 26%. It is expected that the increase in brassinosteroid levels and plant biomass produced in response to an increase in DAS5 gene expression may increase disease resistance, thermotolerance and general stress protection.