Tobacco ZFT1, a Transcriptional Repressor with a Cys sub(2)/His sub(2) Type Zinc Finger Motif that Functions in Spermine-Signaling Pathway

• Published in: Plant molecular biology 2005-10, Vol.59 (3), p.435-448
• Main Authors: Uehara, Yukiko, Takahashi, Yoshihiro, Berberich, Thomas, Miyazaki, Atsushi, Takahashi, Hideki, Matsui, Kyoko, Ohme-Takagi, Masaru, Saitoh, Hiromasa, Terauchi, Ryohei, Kusano, Tomonobu
• Format: Article
• Language: English
• Subjects: Petunia; Tobacco mosaic virus
• ISSN: 0167-4412; 1573-5028
• DOI: 10.1007/s11103-005-0272-0

We previously proposed that a spermine (Spm)-mediated signal transduction pathway is involved in the hypersensitive response induced by Tobacco mosaic virus (TMV) in tobacco plants. To identify regulatory component(s) of this pathway, we surveyed a tobacco cDNA library and found that the ZFT1 gene, which encodes a Cys sub(2)/His sub(2) type zinc-finger protein, is Spm-responsive. ZFT1 was not induced by two other polyamines, putrescine and spermidine, or by salicylic acid (SA), jasmonic acid or ethylene. Furthermore, ZFT1 was upregulated in TMV- inoculated tobacco plants in an N gene-dependent manner. Notably, induction of ZFT1 by Spm and by TMV infection was unimpaired in NahG-transgenic tobacco plants, indicating that cross-talk with an SA signaling pathway is not involved in this response. Within the Spm-signaling pathway, we found that ZFT1 functioned downstream of both mitochondrial dysfunction and mitogen-activated protein kinase activation. The ZFT1 protein has two zinc finger motifs and shows a high degree of similarity to ZPT2-3 in petunia and SCOF1 in soybean. However, unlike the latter two proteins, ZFT1 binds to the EP1S sequence and functions as a transcription repressor. Moreover, interestingly, ZFT1 overexpression rendered tobacco plants more tolerant to TMV. Based on the results presented here, we propose that ZFT1 functions as a transcription repressor in a Spm signaling pathway, thereby accelerating necrotic local region formation in tobacco leaves.