RRSV介导microRNA调控的水稻叶片缺刻症状形成机制

MicroRNAs (miRNAs) are an extensive class of endogenous, non-coding, short (21-25 nt) RNA molecules directly involved in regulating gene expression at the transcriptional or post-transcriptional level through the RNA silencing machinery. Plant miRNAs are involved in all aspects of regulation such as development, organ morphogenesis, biotic or abiotic stress responses and other biology processes. Symptoms of virus-infected plants are often very specific to the given virus. The molecular mechanisms involved in viral symptom induction have been extensively studied, but are still poorly understood, especially for RNA viruses. RRSV, a dsRNA virus, is one of the major viral diseases of rice, which belongs to the genus Phytoreovirus in the family Oryzavirus. The viral genome consists of 10 segments of dsRNA. Therefore, it is of great significance to research into mechanism of miRNA induced serrate symptoms in RRSV infected rice. The generation and distribution characteristics of RRSV vsiRNA, the effects of virus on rice miRNA after infection of RRSV and inhibition of RRSV suppressor could be revealed by deep-sequencing technologies. This work can help reveal the pathogenesis of RRSV, as well as the mechanism of rice silencing pathways, which lays the foundation for the research of pathogenesis of dsRNA viruses and symptom development mechanisms through the miRNA machinery.

MicroRNAs是一类内源性的、21-25nt长度的小分子非编码RNA，通过RNA沉默机制在转录和转录后水平调控靶基因表达的一类负调控因子，参与了植物生长发育、器官形态建成以及各种生物和非生物胁迫反应等生物学过程。病毒侵入寄主后诱发各种病害症状，至今，特别对RNA病毒的病害症状形成的分子机制仍然知之甚少。RRSV，一个典型的dsRNA病毒，是水稻生产上的主要病害之一，属于水稻病毒属成员，基因组由10条dsRNA组成。因此，研究miRNA调控的RRSV感染水稻中叶片缺刻症状形成的分子机制具有重要意义。通过深度测序技术揭示RRSV侵染和在病毒RNA 沉默抑制因子被沉默后, RRSV 介导的vsiRNA的产生和分布特征以及对水稻miRNA的影响；这将有助深入揭示RRSV 致病机理，以及在水稻RNA 沉默路径中的作用机制，为研究miRNA 调控的dsRNA 病毒的致病机制和症状形成机制奠定基础。

微小分子RNA（microRNA，miRNA）是植物生长发育和病毒-寄主互作的重要调控者。然而，关于miRNA促进病毒侵染或者增强寄主感病性及miRNA介导的抗病毒防御反应的研究甚少。本项目研究发现水稻锯齿叶矮缩病毒（Rice ragged stunt virus，RRSV）显著诱导了miR319的表达，而抑制了miR319调控的靶基因TCP家族基因的表达，其中TCP21的表达受到RRSV抑制程度最为明显。另外，miR319过表达转基因水稻和TCP21RNAi转基因水稻显示出类似病害症状的表型，且与野生型水稻相比，二者对RRSV的敏感性显著提高。然而，RRSV接种TCP21转基因过表达水稻，尤其是miR319-resistant TCP21转基因过表达水稻，则显示较弱的病害症状。已有研究报道表明，miR319及其靶基因TCPs参与调控在抗病防御反应中起重要作用的植物激素茉莉酸的生物合成。因此，我们研究发现miR319/TCP21也调控了水稻茉莉酸通路。这些结果表明，RRSV通过调控水稻miR319一方面促进病毒侵染，一方面诱导了病害症状的产生。