How do bacteria cause the uncontrolled plant-cell growth seen in crown gall?

In the context of plant pathology, the uncontrolled cell growth observed in crown gall is caused by the bacterium Agrobacterium tumefaciens.12

The transformation of a normal plant cell into one that undergoes excessive multiplication is driven by a plasmid—a small, circular piece of DNA—carried by the bacterium. When the bacterium infects a plant, this genetic material is transferred into the host plant's cells. Once integrated, the bacterial DNA directs the plant cell to produce hormones that stimulate rapid, disorganized cell division and growth, resulting in the characteristic tumorous enlargements known as galls.32

This process effectively hijacks the plant's natural growth regulatory systems, which normally rely on a balance of auxins and cytokinins to manage development and differentiation. By forcing the plant to overproduce these growth-promoting substances, the bacterium ensures the proliferation of the tissue required for its own survival and spread.453