Mechanisms of Gene Regulation
van Verk, M.C. , Maltese, F. , Neeleman, L. , Pappaioannou, D. , Bol, J.F. , Linthorst, H.J.M. .
A novel WRKY-factor is involved in induction of PR-1a gene expression by tobacco mosaic virus infection.
Infection with tobacco mosaic virus (TMV) of tobacco plants with the N gene results in salicylic acid (SA)-mediated expression of the PR-1a gene and other defense-related genes. One-hybrid screens identified a novel tobacco WRKY-transcription factor (NtWRKY12) with specific binding sites at positions -859 (Wl-box) and -564 (Wr-box) in the PR-1a promoter. The binding sequence of this factor (TTTTCCAC) deviated significantly from the consensus WRKY-factor binding site ([T]TGAC[C/T]). The Wr-box is in close proximity to binding sites in the PR-1a promoter for TGA (position -582) and Myb1 (position -520) transcription factors. Expression of the NtWRKY12 gene was strongly enhanced by TMV-infection or application of exogenous SA. PR-1a promoter / GUS fusions with mutations in the promoter sequence were inserted in the genome of tobacco plants. GUS-expression by the wild-type construct was strongly increased by TMV-infection of the plants or application of SA. Mutations in NtWRKY12 binding sites Wl or Wr, or in the TGA binding site each reduced GUS expression mediated by TMV and SA. A double mutation affecting both the Wl and Wr sites further reduced GUS expression, whereas a deletion removing the Wr, TGA and Myb1 sites abolished induction of GUS-expression by TMV or SA. The results indicate that NtWRKY12 acts synergistically with TGA and/or Myb1 in the induction of PR-1a gene expression. Agroinfiltration of tobacco with Agrobacterium tumefaciens elicited expression of the endogenous PR-1a gene and expression of a PR-1a promoter / GUS-fusion in the T-DNA vector. Mutations in the Wl and Wr sites in the PR-1a / GUS fusion revealed that NtWRKY12 is also involved in expression of the PR-1a gene induced by bacterial elicitors.
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1 - Leiden University, Institute of Biology, Gorlaeus Laboratories
2 - Leiden University, Institute of Biology, Gorlaeus Laboratories, Einsteinweg 55, P.O. box 9502, Leiden, 2300RA, The Netherlands
defence- and repair-related proteins.
Presentation Type: Plant Biology Abstract
Location: Exhibit Hall (Northeast, Southwest & Southeast)/Hilton
Date: Sunday, July 8th, 2007
Time: 8:00 AM