Direct Gene Transfer into Plant Protoplasts

The techniques of plant molecular biology have advanced rapidly in the last 5 yr, and, for a number of plant species, including some crops, it is now possible to bypass traditional plant breeding techniques and introduce specific genes directly. The earliest reports of the transformation of plants with foreign genes exploited the fact that the soil bacterium Agrobacterium tumefaciens , which induces the formation of crown galls, transfers part of a plasmid (the tumor-inducing, Ti, plasmid) into its host (e.g., ref. 1 ). The isolation and modification of this plasmid by the insertion of one or more structural genes together with regulatory elements has provided the means of genetically manipulating intact plants, cultured plant tissues, and protoplasts.