Ciftci-Yilmaz Sultan, Morsy Mustafa R, Song Luhua, Coutu Alicia, Krizek Beth A, Lewis Michael W, Warren Daniel, Cushman John, Connolly Erin L, Mittler Ron
Department of Biochemistry and Molecular Biology, University of Nevada, Reno, Nevada 89557, USA.
J Biol Chem. 2007 Mar 23;282(12):9260-8. doi: 10.1074/jbc.M611093200. Epub 2007 Jan 25.
Cys2/His2-type zinc finger proteins, which contain the EAR transcriptional repressor domain, are thought to play a key role in regulating the defense response of plants to biotic and abiotic stress conditions. Although constitutive expression of several of these proteins was shown to enhance the tolerance of transgenic plants to abiotic stress, it is not clear whether the EAR-motif of these proteins is involved in this function. In addition, it is not clear whether suppression of plant growth, induced in transgenic plants by different Cys2/His2 EAR-containing proteins, is mediated by the EAR-domain. Here we report that transgenic Arabidopsis plants constitutively expressing the Cys2/His2 zinc finger protein Zat7 have suppressed growth and are more tolerant to salinity stress. A deletion or a mutation of the EAR-motif of Zat7 abolishes salinity tolerance without affecting growth suppression. These results demonstrate that the EAR-motif of Zat7 is directly involved in enhancing the tolerance of transgenic plants to salinity stress. In contrast, the EAR-motif appears not to be involved in suppressing the growth of transgenic plants. Further analysis of Zat7 using RNAi lines suggests that Zat7 functions in Arabidopsis to suppress a repressor of defense responses. A yeast two-hybrid analysis identified putative interactors of Zat7 and the EAR-domain, including WRKY70 and HASTY, a protein involved in miRNA transport. Our findings demonstrate that the EAR-domain of Cys2/His2-type zinc finger proteins plays a key role in the defense response of Arabidopsis to abiotic stresses.
含有EAR转录抑制结构域的Cys2/His2型锌指蛋白被认为在调节植物对生物和非生物胁迫条件的防御反应中起关键作用。尽管已表明其中几种蛋白的组成型表达可增强转基因植物对非生物胁迫的耐受性，但尚不清楚这些蛋白的EAR基序是否参与此功能。此外，尚不清楚由不同的含Cys2/His2 EAR的蛋白在转基因植物中诱导的植物生长抑制是否由EAR结构域介导。在此我们报道，组成型表达Cys2/His2锌指蛋白Zat7的转基因拟南芥植物生长受到抑制，但对盐胁迫更具耐受性。Zat7的EAR基序缺失或突变会消除耐盐性，而不影响生长抑制。这些结果表明，Zat7的EAR基序直接参与增强转基因植物对盐胁迫的耐受性。相反，EAR基序似乎不参与抑制转基因植物的生长。使用RNAi株系对Zat7进行的进一步分析表明，Zat7在拟南芥中发挥作用以抑制防御反应的抑制因子。酵母双杂交分析鉴定出Zat7和EAR结构域的推定相互作用蛋白，包括WRKY70和参与miRNA转运的蛋白HASTY。我们的研究结果表明，Cys2/His2型锌指蛋白的EAR结构域在拟南芥对非生物胁迫的防御反应中起关键作用。
