In Arabidopsis thaliana, a mitogen-activated protein kinase pathway, MEKK1–MKK1/MKK2–MPK4, is important for basal resistance and disruption of this pathway results in dwarf, autoimmune phenotypes. To elucidate the complex mechanisms activated by the disruption of this pathway, we have previously developed a mutant screening system based on a dwarf autoimmune line that overexpressed the N-terminal regulatory domain of MEKK1. Here, we report that the second group of mutants, smn2, had defects in the SMN2 gene, encoding a DEAD-box RNA helicase. SMN2 is identical to HEN2, whose function is vital for the nuclear RNA exosome because it provides non-ribosomal RNA specificity for RNA turnover, RNA quality control and RNA processing. Aberrant SMN1/RPS6 transcripts were detected in smn2 and hen2 mutants. Disease resistance against Pseudomonas syringae pv. tomato DC3000 (hopA1), which is conferred by SMN1/RPS6, was decreased in smn2 mutants, suggesting a functional connection between SMN1/RPS6 and SMN2/HEN2. We produced double mutants mekk1smn2 and mpk4smn2 to determine whether the smn2 mutations suppress the dwarf, autoimmune phenotypes of the mekk1 and mpk4 mutants, as the smn1 mutations do. As expected, the mekk1 and mpk4 phenotypes were suppressed by the smn2 mutations. These results suggested that SMN2 is involved in the proper function of SMN1/RPS6. The Gene Ontology enrichment analysis using RNA-seq data showed that defense genes were downregulated in smn2, suggesting a positive contribution of SMN2 to the genome-wide expression of defense genes. In conclusion, this study provides novel insight into plant immunity via SMN2/HEN2, an essential component of the nuclear RNA exosome.

中文翻译：

---

拟南芥SMN2 / HEN2，编码DEAD-Box RNA解旋酶，控制抗性基因SMN1 / RPS6的正确表达，并参与mekk1和mpk4突变体的矮化，自身免疫表型。

在拟南芥中，有丝分裂原激活的蛋白激酶途径，MEKK1-MKK1 / MKK2-MPK4，对基础抗性很重要，破坏该途径会导致矮小的自身免疫表型。为了阐明由该途径的破坏激活的复杂机制，我们先前已经开发了一种基于矮人自身免疫株的突变体筛选系统，该矮株自身免疫株过度表达了MEKK1的N端调节域。在这里，我们报告第二组突变体smn2在SMN2基因中存在缺陷，编码DEAD-box RNA解旋酶。SMN2与HEN2相同，其功能对核RNA外泌体至关重要，因为它为RNA转换，RNA质量控制和RNA加工提供了非核糖体RNA特异性。异常SMN1 / RPS6是在检测成绩单SMN2和hen2突变体。抗丁香假单胞菌PV的疾病抗性。番茄DC3000（hopA1），其通过赋予SMN1 / RPS6，在降低SMN2突变体，这表明之间的功能性连接SMN1 / RPS6和SMN2 / HEN2。我们生产了双突变体mekk1smn2和mpk4smn2，以确定是否SMN2突变抑制的侏儒，自身免疫表型MEKK1和MPK4的突变体，为SMN1基因突变做。正如预期的那样，smn2突变抑制了mekk1和mpk4表型。这些结果表明SMN2参与了SMN1 / RPS6的正常功能。使用RNA-seq数据进行的基因本体论富集分析表明，防御基因在smn2中被下调，表明SMN2发挥了积极作用防御基因全基因组表达。总之，这项研究提供了通过SMN2 / HEN2（核RNA外泌体的重要组成部分）对植物免疫的新见解。