tumour-inducing principle

A plasmid carried by the bacterium Agrobacterium tumefaciens, which causes crown gall disease in plants. The plasmid is necessary for the transformation of normal host tissue into tumour tissue. It is believed that this is brought about by the incorporation of the plasmid into the plant genome. Tissue removed from crown gall tumours can be grown in culture without the addition of auxin and cytokinin.