Over-expression of TGA5, which encodes a bZIP transcription factor that interacts with NIM1/NPR1, confers SAR-independent resistance in Arabidopsis thaliana to Peronospora parasitica
Over-expression of TGA5, which encodes a bZIP transcription factor that interacts with NIM1/NPR1, confers SAR-independent resistance in Arabidopsis thaliana to Peronospora parasitica
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DOI：
10.1046/j.1365-313x.2001.01411.x
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发表时间：
2002-10-01
期刊：
影响因子：
7.2
通讯作者：
Delaney, TP
中科院分区：
文献类型：
--
作者：
Kim, HS;Delaney, TP
拟南芥NIM1/NPR1基因产物是病原菌、水杨酸(SA)或合成SA类似物诱导系统获得抗性(SAR)所必需的。在酵母双杂交筛选中，我们鉴定了两个NIM1/NPR1相互作用蛋白TGA2和TGA5，它们属于碱性区域亮氨酸拉链(BZIP)转录因子家族。TGA2和TGA5在酵母和体外都与NIM1/NPR1有很强的相互作用，并识别存在于几个致病相关基因的启动子中的AS-1顺式元件，如PR-1。为了确定TGA2和TGA5在NIM1/NPR1介导的抗病中可能发挥的作用，我们将这两个基因的正义和反义版本引入到转基因拟南芥中。对TGA2转基因植株的鉴定表明，在病原体侵染或INA处理后，TGA2的抑制或过表达对PR-1的表达或SAR的诱导没有显著影响。令人惊讶的是，所有产生的TGA5反义转基因植株都显示出比未转化对照植株TGA5转录产物的积累增加，而TGA5正义系的TGA5 mRNA水平没有显著增加。有趣的是，反义TGA5mRNA的高水平伴随着对卵菌病原菌Peronospora parasitica的高毒力分离物的显著抗性。此外，在接种寄生疫霉或用INA处理后，抗性与SAR连锁的PR-1基因产物的积累没有耦合，这表明这些植物表达了一种强大的、PR-1不依赖的抗性机制。当TGA5积累系与nim1-1突变或nahG(水杨酸羟基酶)转基因结合时，保持了抗性，这表明这些植物的抗性是由SA和SAR不依赖的机制造成的。
The Arabidopsis thaliana NIM1/NPR1 gene product is required for induction of systemic acquired resistance (SAR) by pathogens, salicylic acid (SA) or synthetic SA analogs. We identified, in a yeast two-hybrid screen, two NIM1/NPR1 interacting proteins, TGA2 and TGA5, which belong to the basic region, leucine zipper (bZIP) family of transcription factors. Both TGA2 and TGA5 strongly interact with NIM1/NPR1 in yeast and in vitro, and recognize the as-1 cis element found within the promoter of several pathogenesis-related genes, such as PR-1. To determine the role TGA2 and TGA5 may play in NIM1/NPR1-mediated disease resistance, we introduced sense and antisense versions of both genes into transgenic Arabidopsis plants. Characterization of TGA2 transgenic plants revealed that inhibition or overexpression of TGA2 does not significantly affect PR-1 expression or induction of SAR after pathogen infection or INA treatment. Surprisingly, all TGA5-antisense transgenic plants produced showed increased accumulation of TGA5 transcripts compared with untransformed control plants, while the TGA5-sense lines showed no significant increase in TGA5 mRNA levels. Interestingly, the high level of TGA5 mRNA in the antisense lines was accompanied by significant resistance to a highly virulent isolate of the oomycete pathogen Peronospora parasitica. Further, resistance was not coupled to accumulation of products from the SAR-linked PR-1 gene following inoculation with P. parasitica or treatment with INA, indicating that these plants express a robust, PR-1-independent resistance mechanism. Resistance was retained when a TGA5-accumulating line was combined genetically with a nim1-1 mutation or nahG (salicylate hydroxylase) transgene, indicating that resistance in these plants is due to an SA and SAR-independent mechanism.