Department of Plant Biology, Cornell University, Ithaca, NY 14853, USA.
Plant J. 2010 May;62(3):357-66. doi: 10.1111/j.1365-313X.2010.04160.x. Epub 2010 Feb 1.
Evasion or active suppression of host defenses are critical strategies employed by biotrophic phytopathogens and hemibiotrophs whose infection mechanism includes sequential biotrophic and necrotrophic stages. Although defense suppression by secreted effector proteins has been well studied in bacteria, equivalent systems in fungi and oomycetes are poorly understood. We report the characterization of SNE1 (suppressor of necrosis 1), a gene encoding a secreted protein from the hemibiotrophic oomycete Phytophthora infestans that is specifically expressed at the transcriptional level during biotrophic growth within the host plant tomato (Solanum lycopersicum). Using transient expression assays, we show that SNE1 suppresses the action of secreted cell death-inducing effectors from Phytophthora that are expressed during the necrotrophic growth phase, as well as programmed cell death mediated by a range of Avr-R protein interactions. We also report that SNE1 contains predicted NLS motifs and translocates to the plant nucleus in transient expression studies. A conceptual model is presented in which the sequential coordinated secretion of antagonistic effectors by P. infestans first suppresses, but then induces, host cell death, thereby providing a highly regulated means to control the transition from biotrophy to necrotrophy.
逃避或主动抑制宿主防御是生物营养型植物病原体和半生物营养型病原体采用的关键策略，其感染机制包括顺序的生物营养型和坏死型阶段。尽管分泌效应蛋白的防御抑制在细菌中得到了很好的研究，但真菌和卵菌中的等效系统了解甚少。我们报告了 SNE1（坏死抑制 1）的特征，该基因编码来自半生物营养型卵菌致病疫霉的一种分泌蛋白，在宿主植物番茄（Solanum lycopersicum）中的生物营养型生长过程中在转录水平上特异性表达。使用瞬时表达测定，我们表明 SNE1 抑制了在坏死型生长阶段表达的来自致病疫霉的分泌细胞死亡诱导效应物的作用，以及由一系列 Avr-R 蛋白相互作用介导的程序性细胞死亡。我们还报告说，SNE1 包含预测的核定位信号基序，并在瞬时表达研究中转录到植物细胞核中。提出了一个概念模型，其中致病疫霉的拮抗效应物的顺序协调分泌首先抑制，但随后诱导宿主细胞死亡，从而为控制从生物营养型到坏死型的转变提供了一种高度调控的手段。
