ACC deaminase-producing bacteria inhibit crown gall formation in tomato plantsinfected by Agrobacterium tumefaciens or A. vitis

Abstract: The plant hormone ethylene plays a key role in the development of crown galls, causedby oncogenic Agrobacterium. Many plant growth-promoting bacteria (PGPB) produce theenzyme 1-aminocyclo-propane-1-carboxylate (ACC) deaminase (ACCD) which can degradeACC, the immediate precursor of ethylene in plants, to α-ketobutyrate and ammonia and therebylower plant ethylene levels. In the present work, we have shown that the ACCD producing PGPBstrains Pseudomonas putida UW4 and Burkholderia phytofirmans PsJN as well as strainAzospirillum brasilense Cd1843 (SP7) transformed by plasmid pRKTACC carrying the acdSgene from UW4 under the tetracycline resistance (tet) promoter are able to significantly decreasedevelopment of crown galls on tomato plants inoculated with strain A. tumefaciens Sh-1 orA. vitis S4. The results suggest that ACCD provided by PGPB alter the balance of ethylene andother phytohormones essential for tumorigenesis in plants transformed by pathogenicagrobacteria.