A variety of expression elements including promoters, enhancers, and introns regulate when and where in a plant a gene is turned on to produce a protein. Every trait gene that is inserted into a plant must be combined with appropriate regulatory elements to control its expression. It is the combination of these expression elements (which we will collectively refer to as the promoter for brevity) and the trait gene that produces the desired phenotype.
The first set of commercial biotech crops contained single trait genes that were driven primarily by the 35S CaMV promoter. More recently, commercialized biotech varieties have been developed with multiple or stacked traits for insect resistance (IR) and herbicide tolerance (HT). In 2011, 49% of the corn and 58% of the cotton grown in the US contained stacked IR and HT traits. The development of second generation biotech crops, with traits such as drought tolerance or more efficient use of nitrogen, will require even greater numbers of stacked trait genes.
This presents several challenges. First, the use of the same promoter to express multiple genes can lead to gene silencing. Second, some of the newly discovered trait genes will require finer expression control to work effectively. To address these issues, multiple modes of gene expression regulation will be needed. Through our expression element discovery program, Grassroots is developing a toolbox of modular expression elements to meet the growing gene regulation needs of the biotechnology industry. Using a proprietary technology, we have particular expertise in designing completely synthetic expression elements. GrassRoots’ synthetic expression elements can confer novel gene expression patterns, reduce silencing issues, and provide increased IP protection for transgenic traits.