Opines -

As a general rule, T -DNA transformed plant cells synthesize opines. Opines are plant metabolites synthesized under the control of T-DNA, which can be specifically catabolized by the inciting bacteria and thus used as a carbon and nitrogen source. The presence of these opines in plant tissue is therefore the most conclusive criterion to indicate.

Agrobacterium as a causative agent for plant cell transformation. Opines distinguish Agrobacteria from other bacteria in the rhizosphere. Agrobacteria are able to utilize opines they produce as specific energy, nitrogen, and carbon source, thus providing a competitive advantage in the crown gall rhizosphere to the inciting agrobacteria over other soil organisms.

Moreover, the opines released from the transformed plant cells induce the conjugative transfer of the inciting Ti plasmid, thus spreading the Ti plasmid in opportune circumstances. The different groups of opines are listed.

The particular opine produced depends on the strain of bacterium infecting the plant. Some strains result in the production of a nopaline, others cause octopine synthesis; in each case the bacterium can use only that particular opine whose production it causes. The enzymes coded for are nopaline or octopine synthases and their respective genes are labelled nos and ocs.