The plant biotechnology-based products that have been, or soon will be, commercialized have been generated primarily through one or other of two pathways: some products have been developed through identification of natural variants or through chemicalor genetic mutation and subsequent breeding strategies; others have been developed using molecular biology methods. These two pathways for product development are complementary, and each has its own advantages. The first, or 'genetic' approach, does notrequire prior knowledge of biosyn-thetic pathways or of the gene, or genes, controlling a particular trait. The molecular biology approach usually requires an understanding of relevant pathways and their control points but, once a gene has been cloned,targeted modifications can be made that are not readily accessible through the genetic approach. These modifications include regulating gene expression in a tissue- or organ-specific manner, or in response to exogenous chemical treatments, amplifying orsuppressing gene expression, and creating site-specific mutations in genes. Multiple genes can be introduced simultaneously to achieve a particular composition in a complex pathway, or to create plants with several value added traits. In addition, genescan be introduced that are synthetic in origin, or that are derived from microbes or from non-cross-breeding plant species.
展开▼
