Molecular Plant-Microbe Interactions (Feb 2012)

The Type III Effector HsvG of the Gall-Forming Pantoea agglomerans Mediates Expression of the Host Gene HSVGT

  • Gal Nissan,
  • Shulamit Manulis-Sasson,
  • Laura Chalupowicz,
  • Doron Teper,
  • Adva Yeheskel,
  • Metsada Pasmanik-Chor,
  • Guido Sessa,
  • Isaac Barash

DOI
https://doi.org/10.1094/MPMI-06-11-0173
Journal volume & issue
Vol. 25, no. 2
pp. 231 – 240

Abstract

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The type III effector HsvG of the gall-forming Pantoea agglomerans pv. gypsophilae is a DNA-binding protein that is imported to the host nucleus and involved in host specificity. The DNA-binding region of HsvG was delineated to 266 amino acids located within a secondary structure region near the N-terminus of the protein but did not display any homology to canonical DNA-binding motifs. A binding site selection procedure was used to isolate a target gene of HsvG, named HSVGT, in Gypsophila paniculata. HSVGT is a predicted acidic protein of the DnaJ family with 244 amino acids. It harbors characteristic conserved motifs of a eukaryotic transcription factor, including a bipartite nuclear localization signal, zinc finger, and leucine zipper DNA-binding motifs. Quantitative real-time polymerase chain reaction analysis demonstrated that HSVGT transcription is specifically induced in planta within 2 h after inoculation with the wild-type P. agglomerans pv. gypsophilae compared with the hsvG mutant. Induction of HSVGT reached a peak of sixfold at 4 h after inoculation and progressively declined thereafter. Gel-shift assay demonstrated that HsvG binds to the HSVGT promoter, indicating that HSVGT is a direct target of HsvG. Our results support the hypothesis that HsvG functions as a transcription factor in gypsophila.