Expression of Ti plasmid genes in monocotyledonous plants infected with Agrobacterium tumefaciens

Abstract

When the bacterium Agrobacterium tumefaciens infects a fresh wound site on a dicotyledonous plant, it attaches to the plant cell wall and introduces a piece of its Ti plasmid DNA into the plant cell via an unknown mechanism^1–4. This piece of Ti plasmid DNA (the T-DNA) becomes integrated in the nuclear genome of the plant cell and is transcribed into a specific number of different transcripts. The T-DNA renders the plant cell tumorous, and also codes for enzymes involved in the synthesis of certain tumour-specific compounds called opines. Any DNA segment inserted into the T-region of the Ti plasmid by genetic manipulation seems to be co-transferred to the plant cell by A. tumefaciens. Thus, the Ti plasmid offers great potential as a vector for the genetic engineering of plant cells. However, as monocots are not susceptible to tumour formation by A. tumefaciens, it is generally believed that the Ti plasmid can be used as a vector for dicotyledonous plants only^1–5. This would severely limit the applicability of the Ti plasmid as a vector, as most commercially important crops are monocots. However, we report here data which indicate that the Ti plasmid may be a useful vector for transforming monocotyledonous plant species.