Carstens Maryke, McCrindle Tyronne K, Adams Nicolette, Diener Anastashia, Guzha Delroy T, Murray Shane L, Parker Jane E, Denby Katherine J, Ingle Robert A
Department of Molecular and Cell Biology, University of Cape Town, Rondebosch, South Africa.
Department of Plant Microbe Interactions, Max Planck Institute for Plant Breeding Research, Köln, Germany.
PLoS One. 2014 Oct 10;9(10):e109853. doi: 10.1371/journal.pone.0109853. eCollection 2014.
The Arabidopsis constitutive induced resistance 1 (cir1) mutant displays salicylic acid (SA)-dependent constitutive expression of defence genes and enhanced resistance to biotrophic pathogens. To further characterise the role of CIR1 in plant immunity we conducted epistasis analyses with two key components of the SA-signalling branch of the defence network, ENHANCED DISEASE SUSCEPTIBILITY1 (EDS1) and PHYTOALEXIN DEFICIENT4 (PAD4). We demonstrate that the constitutive defence phenotypes of cir1 require both EDS1 and PAD4, indicating that CIR1 lies upstream of the EDS1-PAD4 regulatory node in the immune signalling network. In light of this finding we examined EDS1 expression in cir1 and observed increased protein, but not mRNA levels in this mutant, suggesting that CIR1 might act as a negative regulator of EDS1 via a post-transcriptional mechanism. Finally, as environmental temperature is known to influence the outcome of plant-pathogen interactions, we analysed cir1 plants grown at 18, 22 or 25°C. We found that susceptibility to Pseudomonas syringae pv. tomato (Pst) DC3000 is modulated by temperature in cir1. Greatest resistance to this pathogen (relative to PR-1:LUC control plants) was observed at 18°C, while at 25°C no difference in susceptibility between cir1 and control plants was apparent. The increase in resistance to Pst DC3000 at 18°C correlated with a stunted growth phenotype, suggesting that activation of defence responses may be enhanced at lower temperatures in the cir1 mutant.
拟南芥组成型诱导抗性1（cir1）突变体表现出防御基因的水杨酸（SA）依赖性组成型表达，并增强了对活体营养型病原体的抗性。为了进一步阐明CIR1在植物免疫中的作用，我们利用防御网络中SA信号分支的两个关键组分，即增强的疾病易感性1（EDS1）和植物抗毒素缺陷4（PAD4）进行了上位性分析。我们证明cir1的组成型防御表型需要EDS1和PAD4两者，这表明CIR1在免疫信号网络中位于EDS1 - PAD4调节节点的上游。鉴于这一发现，我们检测了cir1中EDS1的表达，观察到该突变体中蛋白质水平增加，但mRNA水平未增加，这表明CIR1可能通过转录后机制作为EDS1的负调节因子。最后，由于已知环境温度会影响植物 - 病原体相互作用的结果，我们分析了在18、22或25°C下生长的cir1植株。我们发现cir1对丁香假单胞菌番茄致病变种（Pst）DC3000的易感性受温度调节。在18°C时观察到对该病原体的抗性最强（相对于PR - 1:LUC对照植株），而在25°C时，cir1和对照植株之间的易感性没有明显差异。在18°C时对Pst DC3000抗性的增加与生长发育迟缓的表型相关，这表明在较低温度下cir1突变体中防御反应的激活可能会增强。
