Worley Jay N, Pombo Marina A, Zheng Yi, Dunham Diane M, Myers Christopher R, Fei Zhangjun, Martin Gregory B
Boyce Thompson Institute for Plant Research, Ithaca, NY, 14853-1801, USA.
Institute of Biotechnology, Cornell University, Ithaca, NY, 14853-1801, USA.
BMC Genomics. 2016 Mar 14;17:229. doi: 10.1186/s12864-016-2534-4.
Effector proteins are translocated into host cells by plant-pathogens to undermine pattern-triggered immunity (PTI), the plant response to microbe-associated molecular patterns that interferes with the infection process. Individual effectors are found in variable repertoires where some constituents target the same pathways. The effector protein AvrPto from Pseudomonas syringae has a core domain (CD) and C-terminal domain (CTD) that each promotes bacterial growth and virulence in tomato. The individual contributions of each domain and whether they act redundantly is unknown.
We use RNA-Seq to elucidate the contribution of the CD and CTD to the suppression of PTI in tomato leaves 6 h after inoculation. Unexpectedly, each domain alters transcript levels of essentially the same genes but to a different degree. This difference, when quantified, reveals that although targeting the same host genes, the two domains act synergistically. AvrPto has a relatively greater effect on genes whose expression is suppressed during PTI, and the effect on these genes appears to be diminished by saturation.
RNA-Seq profiles can be used to observe relative contributions of effector subdomains to PTI suppression. Our analysis shows the CD and CTD multiplicatively affect the same gene transcript levels with a greater relative impact on genes whose expression is suppressed during PTI. The higher degree of up-regulation versus down-regulation during PTI is plausibly an evolutionary adaptation against effectors that target immune signaling.
效应蛋白由植物病原体转运至宿主细胞中，以破坏模式触发免疫（PTI），即植物对微生物相关分子模式的反应，该反应会干扰感染过程。在不同的效应蛋白库中可发现单个效应蛋白，其中一些成分靶向相同的途径。丁香假单胞菌的效应蛋白AvrPto具有一个核心结构域（CD）和一个C末端结构域（CTD），每个结构域都能促进番茄中的细菌生长和毒力。每个结构域的单独作用以及它们是否冗余发挥作用尚不清楚。
我们使用RNA测序来阐明接种后6小时CD和CTD对番茄叶片中PTI抑制的作用。出乎意料的是，每个结构域都会改变基本相同基因的转录水平，但程度不同。当对这种差异进行量化时发现，尽管靶向相同的宿主基因，但这两个结构域协同发挥作用。AvrPto对PTI期间表达被抑制的基因影响相对较大，并且对这些基因的影响似乎会因饱和而减弱。
RNA测序图谱可用于观察效应子亚结构域对PTI抑制的相对作用。我们的分析表明，CD和CTD对相同基因转录水平有相乘效应，对PTI期间表达被抑制的基因有更大的相对影响。PTI期间上调程度高于下调程度可能是针对靶向免疫信号的效应子的一种进化适应。
