Major biocontrol of plant tumors targets tRNA synthetase.

Crops can be devastated by pathogenic strains of Agrobacterium tumefaciens that cause crown gall tumors. This devastation can be prevented by the nonpathogenic biocontrol agent A. radiobacter K84, which prevents disease by production of the "Trojan horse" toxin agrocin 84, which is specifically imported into tumorgenic A. tumefaciens strains to cause cell death. We demonstrate that this biocontrol agent targets A. tumefaciens leucyl-tRNA synthetase (LeuRS), an essential enzyme for cell viability, while the agent itself survives by having a second, self-protective copy of the synthetase. In principle, this strategy from nature could be applied to other crop diseases by direct intervention.