All effects coming from the infection of R. fascians do not depend on plant cells' transformation (as they do in Agrobacterium tumefaciens or Agrobacterium rhizogenes), but on expression of virulence-related genes of bacterium and on the production of compounds that can interfere with normal plant growth and development.

During the infection, R. fascians usually stays outside vegetal tissues, near a junction or cavity of a plant's cell walls, maybe to avoid environmental stresses.

Using deletion mutations, it was possible to identify three loci on the plasmid: fas, att, and hyp, and one locus on the chromosome, vic.

In fact, attA, attD & attH are involved in betalactamase synthesis, but no traces of those compounds were found in culture supernatants.

[2] The only known gene is vicA, the fourth gene in the operon, whose product is a Mas homologue, a protein needed for the switch from citric acid cycle to glyoxylate cycle, both for metabolic reasons and to avoid glyoxylate accumulation, which is toxic for the bacteria.

Mutations in vicA reduce virulence due to incapacity of R. fascians to resist glyoxylate accumulation.

In particular, most of the effects are connected to auxin and cytokinin, such as: formation of green islands on leaves, wrinkling of laminae, bud proliferation, delay of senescence, and inhibition of lateral roots.

Abscisic acid represses growth, so a block of production is needed to allow proliferation of cells in leafy galls.

Gibberellic acid controls cellular differentiation, so its block is needed for maintenance of meristematic cells and for their proliferation.