MiR2/9与N-homolog蛋白在SMV-大豆互作中的作用研究

Soybean Mosaic Virus (SMV) is a plant virus that infects soybean worldwide, causing severe yield reductions. While the progress has been made on the study of molecular marker and QTL mapping about SMV resistance gene, the gene itself is still elusive. N protein is a TMV-resistant protein from tobacco and it belongs to NBS-LRR protein family, which contribute to most of the disease resistant proteins found in plants to date. There are 35 N-homologs on soybean chromosome. Some of these N-homologs are associated with the disease resistant QTL on the chromosome. We also found that these N-homologs are predicted targets of miR-2 and miR-9. Expressions of some of the N-homologs are shortly induced in 1h post SMV infection. However, they are down-regulated when successful infection is established after longer infection of SMV, while the level of miR-2 and miR-9 is up-regulated, suggesting a correlative expression of miR-2/9 and their putative target N-homologs. We hypothesize that soybean N-homologs are playing important roles in soybean resistance to SMV, and SMV antagonize this resistance by regulating the level of miR-2/9. We will unveil the molecular mechanisms of SMV-soybean interaction by verifying the functions of soybean N-homologs in SMV infection and the involvements of miR-2 and miR-9 during this process.

SMV病毒是一种世界性大豆病害。目前在SMV抗性基因的分子标记和QTL定位研究方面有了一些进展，但是尚未克隆到抗SMV基因。N蛋白是个广泛研究的抗TMV蛋白，属于NBS-LRR蛋白家族。大豆基因组上有35个N-homolog基因，发现其为miR-2和miR-9的预测靶标。部分N-homolog基因在染色体上的位置与已知的抗病QTL紧密连锁。我们发现一些N-homolog基因在SMV侵染后短时间内诱导表达。随着SMV的成功侵染，miR-2和miR-9的水平上升，而这些N-homolog基因的表达又明显下调。我们推测大豆N-homolog基因在SMV抗性方面起着重要的作用，而SMV通过调控一些miRNAs的水平来抵御大豆对其的防卫反应。因此，本项目拟鉴定这35个N-homolog基因的功能，并检测miR-2和miR-9在其中的调节作用，初步揭示SMV-大豆互作的分子机理，具有重要理论意义。

SMV病毒是一种世界性大豆病害。目前在SMV抗性基因的分子标记和QTL定位研究方面有了一些进展，但是尚未克隆到抗SMV基因。N蛋白是个广泛研究的抗TMV蛋白，属于NBS-LRR蛋白家族。大豆基因组上有35个N-homolog基因，发现其为miR-2和miR-9的预测靶标，且部分N-homolog基因在染色体上的位置与已知的抗病QTL紧密连锁。我们推测大豆N-homolog基因在SMV抗性方面起着重要的作用，而SMV通过调控一些miRNAs的水平来抵抗大豆对其的防御反应。本研究中我们发现大豆GmNH23对SMV，TMV，PVY和PPV等具有广谱抗性。GmNH23为一个编码TIR-NBS-LRR蛋白的抗病毒基因。GmNH23的表达在转录水平上受SMV和SA的调控，转录后水平上受miR2/9的调控。GmNH23基因下游可能通过SA来发挥作用。GmNH23蛋白定位于细胞核内，其N-末端的TIR-NBS结构域为病毒抗性结构域。SMV通过诱导miR2/9来抑制GmNH23的表达，最终达到成功侵染和扩增。我们的结果揭示了miR2/9-GmNH23的调控关系及其在SMV侵染中的作用，理论上为进一步阐明SMV-大豆互作的分子机制打下了基础，同时对大豆的抗病毒分子育种具有广泛的应用前景。