The Molecular Genetics Of Crown Gall Tumorigenesis

The finding that the T-DNA found in different tumor tissues is of a fixed size poses the question of whether T- DNA integrates into plant DNA via a mechanism similar to that by which transposable elements integrate into foreign DNA.

Abstract

The most important characteristic that immediately distinguishes agrobacteria from most other bacteria is their ability to induce tumor formation in plants. Agrobacteria transform “conditioned” plant cells into tumor cells by introducing into them a piece of genetic information which in established plant tumor cells can be recovered as T-DNA integrated into the nuclear plant DNA. Tumor cells characteristically contain a set of unusual amino acid derivatives that have never been found in normal plant cells. Crown gall cells carry a piece of DNA that is homologous to a part of A. turnefuciens DNA integrated into their nuclear DNA. The T-DNA is responsible for the phytohormone-independent growth of tumor cells and encodes enzymes that synthesize opines in the tumor cells. Moreover, the finding that the T-DNA found in different tumor tissues is of a fixed size poses the question of whether T-DNA integrates into plant DNA via a mechanism similar to that by which transposable elements integrate into foreign DNA. The answer to this question is not known. However, it is known that the ends of the T-region are important for tumor induction.