Leafy gall formation by Rhodococcus fascians

Rhodococcus fascians infects a wide range of plants, initiating the formati on of leafy galls that consist of centers of shoot amplification and shoot growth inhibition. R. fascians is an epiphyte but it also can establish end ophytic populations. Bacterial signals involved in symptom development init iate de novo cell division and shoot meristem formation in differentiated t issues. The R. fascians signals exert activities that are distinct from mer e cytokinin effects, and the evidence points to a process that adopted cyto kinin biosynthetic enzymes to form derivatives with unique activity. Genes implicated in leafy gall formation are located on a linear plasmid and are subject to a highly controlling, complex regulatory network, integrating au toregulatory compounds and environmental signals. Leafy galls are considere d as centers with specific metabolic features, a niche where populations of R. fascians experience a selective advantage. Such "metabolic habitat modi fication" might be universal for gall-inducing bacteria.