Zheng Lijia, Zhang Chao, Shi Chaonan, Yang Zhirui, Wang Yu, Zhou Tong, Sun Feng, Wang Hong, Zhao Shanshan, Qin Qingqing, Qiao Rui, Ding Zuomei, Wei Chunhong, Xie Lianhui, Wu Jianguo, Li Yi
State Key Laboratory of Ecological Pest Control for Fujian and Taiwan Crops, Fujian Province Key Laboratory of Plant Virology, Institute of Plant Virology, Fujian Agriculture and Forestry University, Fuzhou, China.
The State Key Laboratory of Protein and Plant Gene Research, College of Life Sciences, Peking University, Beijing, China.
PLoS Pathog. 2017 Oct 4;13(10):e1006662. doi: 10.1371/journal.ppat.1006662. eCollection 2017 Oct.
MicroRNAs (miRNAs) are small regulatory RNAs processed from primary miRNA transcripts, and plant miRNAs play important roles in plant growth, development, and response to infection by microbes. Microbial infections broadly alter miRNA biogenesis, but the underlying mechanisms remain poorly understood. In this study, we report that the Rice stripe virus (RSV)-encoded nonstructural protein 3 (NS3) interacts with OsDRB1, an indispensable component of the rice (Oryza sativa) miRNA-processing complex. Moreover, the NS3-OsDRB1 interaction occurs at the sites required for OsDRB1 self-interaction, which is essential for miRNA biogenesis. Further analysis revealed that NS3 acts as a scaffold between OsDRB1 and pri-miRNAs to regulate their association and aids in vivo processing of pri-miRNAs. Genetic evidence in Arabidopsis showed that NS3 can partially substitute for the function of double-stranded RNA binding domain (dsRBD) of AtDRB1/AtHYL1 during miRNA biogenesis. As a result, NS3 induces the accumulation of several miRNAs, most of which target pivotal genes associated with development or pathogen resistance. In contrast, a mutant version of NS3 (mNS3), which still associated with OsDRB1 but has defects in pri-miRNA binding, reduces accumulation of these miRNAs. Transgenic rice lines expressing NS3 exhibited significantly higher susceptibility to RSV infection compared with non-transgenic wild-type plants, whereas the transgenic lines expressing mNS3 showed a less-sensitive response. Our findings revealed a previously unknown mechanism in which a viral protein hijacks OsDRB1, a key component of the processing complex, for miRNA biogenesis and enhances viral infection and pathogenesis in rice.
微小RNA（miRNA）是从初级miRNA转录本加工而来的小调控RNA，植物miRNA在植物生长、发育以及对微生物感染的反应中发挥重要作用。微生物感染广泛改变miRNA的生物合成，但其潜在机制仍知之甚少。在本研究中，我们报道水稻条纹病毒（RSV）编码的非结构蛋白3（NS3）与OsDRB1相互作用，OsDRB1是水稻（Oryza sativa）miRNA加工复合体中不可或缺的组分。此外，NS3与OsDRB1的相互作用发生在OsDRB1自我相互作用所需的位点，这对miRNA生物合成至关重要。进一步分析表明，NS3作为OsDRB1和初级miRNA（pri-miRNA）之间的支架来调节它们的结合，并有助于pri-miRNA在体内的加工。拟南芥中的遗传学证据表明，在miRNA生物合成过程中，NS3可以部分替代AtDRB1/AtHYL1的双链RNA结合结构域（dsRBD）的功能。结果，NS3诱导几种miRNA的积累，其中大多数靶向与发育或病原体抗性相关的关键基因。相比之下，NS3的突变体版本（mNS3）虽然仍与OsDRB1相关，但在pri-miRNA结合方面存在缺陷，会减少这些miRNA的积累。与非转基因野生型植物相比，表达NS3的转基因水稻品系对RSV感染表现出明显更高程度的易感性，而表达mNS3的转基因品系则表现出较不敏感的反应。我们的研究结果揭示了一种先前未知的机制，即病毒蛋白劫持加工复合体的关键组分OsDRB1用于miRNA生物合成，并增强水稻中的病毒感染和发病机制。
