4.4. Production of T-DNA strand

The right and left border sequence of T-DNA are identified by vir D1/ vir D2 protein complex and vir D2 produces single stranded DNA (ss-T-DNA). After nicking, vir D2 becomes covalently attached to the 5'end of ss-T- DNA strand and protect and export the ss-T-DNA to plant cells.

 

4.5. Transfer of T-DNA out the bacterial cell

The ss-T-DNA – vir D2 complex in association with vir E2 is exported from bacterial cell by a ‘T-pilus' (a membrane channel secretary system).

4.6. Transfer T-DNA into plant cell and integration

The single stranded T-DNA–vir D2 complex and other vir proteins cross the plant plasma membrane. In the plant cells, T-DNA gets covered with vir E2. This covering of Vir E2 helps in protection of ss-T-DNA from degradation by nucleases. vir D2 and vir E2 interact with variety of plant proteins which influence the T-DNA transport and integration. The T-DNA – Vir D2 – Vir E2 – plant proteins complex enters the nucleus through nuclear pore complex (NPC). In the nucleus, T-DNA gets integrated into the plant genome by a process referred to as ‘illegitimate recombination'. This process is unlike homologous recombination as it does not depend on extensive region of sequence similarity.