Bhattacharjee Saikat, Zamora Alejandro, Azhar Muhammad Tehseen, Sacco Melanie A, Lambert Lester H, Moffett Peter
Boyce Thompson Institute for Plant Research, Tower Road, Ithaca, NY 14850, USA.
Plant J. 2009 Jun;58(6):940-51. doi: 10.1111/j.1365-313X.2009.03832.x. Epub 2009 Feb 10.
Active resistance to viruses is afforded by plant disease resistance (R) genes, which encode proteins with nucleotide-binding (NB) and leucine-rich repeat (LRR) domains. Upon recognition of pathogen-derived elicitors, these NB-LRR proteins are thought to initiate a number of signaling pathways that lead to pathogen restriction. However, little is known about the molecular mechanisms that ultimately curtail virus accumulation. Here, we show that the co-expression of a plant NB-LRR protein with its cognate elicitor results in an antiviral response that inhibits the translation of virus-encoded proteins in Nicotiana benthamiana. This antiviral response is dependent on viral cis elements, and, upon activation of the NB-LRR protein, viral transcripts accumulate but do not associate with ribosomes. The induced inhibition of viral transcript translation and NB-LRR-mediated virus resistance were compromised by the downregulation of Argonaute4-like genes. Argonaute proteins have been implicated in small RNA-mediated RNA degradation, and in degradation-independent translational control. Our results suggest that the engagement of Argonaute proteins in the specific translational control of viral transcripts is a key factor in virus resistance mediated by NB-LRR proteins.
植物抗病（R）基因赋予植物对病毒的主动抗性，这些基因编码具有核苷酸结合（NB）和富含亮氨酸重复序列（LRR）结构域的蛋白质。在识别病原体衍生的激发子后，这些NB-LRR蛋白被认为会启动一些导致病原体受限制的信号通路。然而，对于最终抑制病毒积累的分子机制知之甚少。在这里，我们表明，植物NB-LRR蛋白与其同源激发子共表达会引发抗病毒反应，该反应抑制本氏烟草中病毒编码蛋白的翻译。这种抗病毒反应依赖于病毒顺式元件，并且在NB-LRR蛋白激活后，病毒转录本积累但不与核糖体结合。类AGO4基因的下调会损害诱导的病毒转录本翻译抑制和NB-LRR介导的病毒抗性。AGO蛋白与小RNA介导的RNA降解以及与降解无关的翻译控制有关。我们的结果表明，AGO蛋白参与病毒转录本的特定翻译控制是NB-LRR蛋白介导的病毒抗性的关键因素。
