Transgenic validation of a promoter strongly inducible by Agrobacterium tumefaciens

Abstract

Abstract 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.