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Uehara Y, Takahashi Y, Berberich T, Miyazaki A, Takahashi H, Matsui K, Ohme-Takagi M, Saitoh H, Terauchi R, Kusano T: Tobacco ZFT1, a transcriptional repressor with a Cys2/His2 type zinc finger motif that functions in spermine-signaling pathway. Plant Mol Biol. 2005 Oct;59(3):435-48.
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 Cys2/His2 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. |
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