Regulation of Oncogene Expression in T-DNA-Transformed Host Plant Cells

PLoS Pathogens

Veselova Svetlana¹  Fabian Imdahl²  Rosalia Deeken²  Yi Zhang²  Wolfgang Dröge-Laser³  Nora Wehner³  Christoph Weiste³  Chil-Woo Lee⁴ 

[1] Institute of Biochemistry and Genetics, Ufa Scientific Centre of Russian Academy of Sciences, Ufa, Russia;Julius-von-Sachs-Institute, Department of Molecular Plant Physiology and Biophysics, University of Wuerzburg, Wuerzburg, Germany;Julius-von-Sachs-Institute, Pharmaceutical Biology, University of Wuerzburg, Wuerzburg, Germany;Leibniz Institute of Plant Biochemistry, Halle /Saale, Germany

关键词: Transcription factors;    Agrobacterium tumefaciens;    Oncogenes;    Auxins;    Arabidopsis thaliana;    Gene expression;    DNA transcription;    Cytokinins;   

DOI  :  10.1371/journal.ppat.1004620

学科分类：生物科学（综合）

来源: Public Library of Science

【 摘 要 】

Virulent Agrobacterium tumefaciens strains integrate their T-DNA into the plant genome where the encoded agrobacterial oncogenes are expressed and cause crown gall disease. Essential for crown gall development are IaaH (indole-3-acetamide hydrolase), IaaM (tryptophan monooxygenase) and Ipt (isopentenyl transferase), which encode enzymes for the biosynthesis of auxin (IaaH, IaaM) and cytokinin (Ipt). Although these oncogenes are well studied as the tumor-inducing principle, nothing is known about the regulation of oncogene expression in plant cells. Our studies show that the intergenic regions (IGRs) between the coding sequences (CDS) of the three oncogenes function as promoters in plant cells. These promoters possess a eukaryotic sequence organization and cis-regulatory elements for the binding of plant transcription factors. WRKY18, WRKY40, WRKY60 and ARF5 were identified as activators of the Ipt promoter whereas IaaH and IaaM is constitutively expressed and no transcription factor further activates their promoters. Consistent with these results, the wrky triple mutant plants in particular, develops smaller crown galls than wild-type and exhibits a reduced Ipt transcription, despite the presence of an intact ARF5 gene. WRKY40 and WRKY60 gene expression is induced by A. tumefaciens within a few hours whereas the ARF5 gene is transcribed later during crown gall development. The WRKY proteins interact with ARF5 in the plant nucleus, but only WRKY40 together with ARF5 synergistically boosts the activation of the Ipt promoter in an auxin-dependent manner. From our data, we propose that A. tumefaciens initially induces WRKY40 gene expression as a pathogen defense response of the host cell. The WRKY protein is recruited to induce Ipt expression, which initiates cytokinin-dependent host cell division. With increasing auxin levels triggered by ubiquitous expression of IaaH and IaaM, ARF5 is activated and interacts with WRKY40 to potentiate Ipt expression and balance cytokinin and auxin levels for further cell proliferation.

【 授权许可】

CC BY