Use of Ti-plasmids for the genetic engineering of plants

These results clearly show that Agrobacterium tumefaciens performs a true genetic manipulation of plants by transferring genes which are actively expressed in plant cells. The exact functions of most T-DNA gene products are not known. However, the action of the genes leading to hormone-independent growth may be formally compared with the effects of a balanced addition of cytokinins plus auxins to the growth medium of normal cells, since that leads to undifferentiated growth with non-transformed plant cells. If this comparison is meaningful, it should be possible to identify the DNA sequences responsible for the hormone-like effects by analyzing tumors induced with mutant Ti-plasmids with a T-region modified by deletion or insertion of DNA in defined locations. This general approach to identify functions of the T-DNA had led to a rough localization of the regions responsible for octopine and nopaline synthesis in plant cells