CONICET, Universidad Nacional de Córdoba, Centro de Investigaciones en Química Biológica de Córdoba (CIQUIBIC), Córdoba, Argentina.
Departamento de Química Biológica Ranwel Caputto, Universidad Nacional de Córdoba, Facultad de Ciencias Químicas, Córdoba, Argentina.
Plant J. 2018 Dec;96(6):1178-1190. doi: 10.1111/tpj.14098. Epub 2018 Nov 23.
Pattern recognition receptors (PRR) and nucleotide-binding leucine-rich repeat proteins (NLR) are major components of the plant immune system responsible for pathogen detection. To date, the transcriptional regulation of PRR/NLR genes is poorly understood. Some PRR/NLR genes are affected by epigenetic changes of neighboring transposable elements (TEs) (cis regulation). We analyzed whether these genes can also respond to changes in the epigenetic marks of distal pericentromeric TEs (trans regulation). We found that Arabidopsis tissues infected with Pseudomonas syringae pv. tomato (Pst) initially induced the expression of pericentromeric TEs, and then repressed it by RNA-directed DNA methylation (RdDM). The latter response was accompanied by the accumulation of small RNAs (sRNAs) mapping to the TEs. Curiously these sRNAs also mapped to distal PRR/NLR genes, which were controlled by RdDM but remained induced in the infected tissues. Then, we used non-infected mom1 (Morpheus' molecule 1) mutants that expressed pericentromeric TEs to test if they lose repression of PRR/NLR genes. mom1 plants activated several PRR/NLR genes that were unlinked to MOM1-targeted TEs, and showed enhanced resistance to Pst. Remarkably, the increased defenses of mom1 were abolished when MOM1/RdDM-mediated pericentromeric TEs silencing was re-established. Therefore, common sRNAs could control PRR/NLR genes and distal pericentromeric TEs and preferentially silence TEs when they are activated.
模式识别受体（PRR）和核苷酸结合富含亮氨酸重复蛋白（NLR）是植物免疫系统的主要组成部分，负责病原体的检测。迄今为止，PRR/NLR 基因的转录调控还知之甚少。一些 PRR/NLR 基因受邻近转座元件（TEs）的表观遗传变化（顺式调控）的影响。我们分析了这些基因是否也能对远距离着丝粒 TE 的表观遗传标记的变化做出响应（反式调控）。我们发现，感染丁香假单胞菌 pv.番茄（Pst）的拟南芥组织最初诱导着丝粒 TE 的表达，然后通过 RNA 指导的 DNA 甲基化（RdDM）抑制它。后者的反应伴随着小 RNA（sRNA）的积累，这些 sRNA 映射到 TEs。奇怪的是，这些 sRNA 也映射到远距离的 PRR/NLR 基因，这些基因受到 RdDM 的控制，但在感染的组织中仍然被诱导。然后，我们使用未感染的 mom1（Morpheus' molecule 1）突变体，这些突变体表达着丝粒 TE，以测试它们是否失去对 PRR/NLR 基因的抑制。mom1 植物激活了几个与 MOM1 靶向 TE 不相关的 PRR/NLR 基因，并表现出对 Pst 的增强抗性。值得注意的是，当重新建立 MOM1/RdDM 介导的着丝粒 TE 沉默时，mom1 增加的防御作用被消除。因此，常见的 sRNA 可以控制 PRR/NLR 基因和远距离着丝粒 TE，并且在它们被激活时优先沉默 TE。
