Transgenic validation of a promoter strongly inducible by Agrobacterium tumefaciens

We report for the first time the isolation and functional characterization of a novel promoter inducible by Agrobacterium tumefaciens, the causative agent of crown gall disease, which leads to significant crop losses. Chemical control of this neoplastic disease is ineffective, since bacterial presence is not essential for T-DNA mediated tumor development. Moreover, A. tumefaciens-mediated transformation, a cornerstone of plant biotechnology, fails in many recalcitrant species due to poorly understood mechanisms. A unique 1086 bp promoter (HyPRO) sharing only ~ 7% similarity with known sequences in NCBI was isolated upstream of the hyp1 gene from Hypericum perforatum. In silico analysis revealed multiple cis regulatory elements (CREs), including WRKY710S, W box, PALBOX, GT1, and VRE, associated with biotic stress responses. Transgenic tobacco plants expressing β glucuronidase (GUS) under HyPRO showed strong induction by A. tumefaciens, significantly higher than induction by Pseudomonas syringae. Upstream truncation of the promoter significantly reduced GUS expression, indicating essential regulatory elements lie upstream of position - 728. This A. tumefaciens responsive promoter offers a valuable tool to dissect plant defense and could enable innovative transgenic strategies for crop improvement and resistance to neoplastic diseases. Characterization of A. tumefaciens-specific CREs using the truncation approach is currently underway in our laboratory.