植物病毒协同调控寄主小RNA胞间迁移的功能分析

RNA interference (RNAi) is considered the main anti-viral defence in plants. One important feature of RNAi is that it can travel from cell to cell and over long distances through the vasculature. The mobile nature of RNAi is potentially crucial for its defensive function, since siRNA derived from invading viruses spread throughout the plant, immunizing distant tissues prior to the arrival of the pathogen. Additionally, miRNAs have also been shown to move, and proposed to act as morphogens, directing plant development. Movement of sRNA is therefore crucial for plant biology; however, how this cell-to-cell and ultimately systemic movement of sRNA is regulated remains mostly elusive. Our recent results have uncovered the C4 protein from Tomato yellow leaf curl virus (TYLCV) as the first viral silencing suppressor known to affect specifically the cell-to-cell movement of RNAi, and the plasma membrane- and plasmodesmata-localized receptor-like kinases BAM1 and BAM2 as the first plant proteins required for this spread of silencing. These findings provide a valuable entry point to gain understanding of a process, the cell-to-cell spread of RNAi, which has remained largely elusive to date. Capitalizing on our previous work and on a large body of preliminary data, we expect that this study will provide unprecedented insight into how the cell-to-cell spread of RNAi, mediated by both siRNA and miRNA, is regulated in plants. On one hand, we will gain further understanding of how BAM1/2 exert their function in this process; on the other, we will identify additional components of the molecular machinery involved in this regulation. Moreover, we will define whether the elements required for the cell-to-cell spread of siRNA and miRNA are common, and if not, attempt to identify the specific machinery mediating the spread of miRNA, using C4, which we have found to also interfere with the miRNA intercellular trafficking, as a probe.

RNA干扰是植物抵抗病毒入侵的主要机制，其重要特征之一是可通过植物的维管系统进行细胞间长距离传播，siRNA的产生可使未被侵染的细胞提前激活免疫防御，对植物抵抗病原物侵染有重要作用。可移动的miRNA可作为形态发生素调控植物发育，故小RNA的移动对植物生物学也十分重要。然而小RNA的胞间以及系统性的传播调控机制尚不清楚。我们近期的研究首次发现仅影响RNAi细胞间移动的沉默抑制蛋白，番茄黄化卷叶病毒TYLCV的C4蛋白；及第一组RNAi传播必需的植物蛋白，定位于细胞膜和胞间连丝的类受体激酶BAM1和BAM2。已有的研究数据提示这项研究有助于深入了解通过siRNA和miRNA介导的RNAi传播机制。我们将进一步探索BMA1/2在这一过程中的作用机制，寻找参与该过程的其他关键组分，探究siRNA和miRNA传播所需条件是否一致。如果不一致，以C4为探针尝试发现miRNA传播所需的特殊组分。

RNA干扰是植物抵抗病毒入侵的主要机制，其重要特征之一是可通过植物的维管系统进行细胞间长距离传播，siRNA的产生可使未被侵染的细胞提前激活免疫防御，对植物抵抗病原物侵染有重要作用。可移动的miRNA可作为形态发生素调控植物发育，故小RNA的移动对植物生物学也十分重要。然而小RNA的胞间以及系统性的传播调控机制尚不清楚。我们近期的研究首次发现仅影响RNAi细胞间移动的沉默抑制蛋白，番茄黄化卷叶病毒TYLCV的C4蛋白；及第一组RNAi传播必需的植物蛋白，定位于细胞膜和胞间连丝的类受体激酶BAM1和BAM2。在此，我们揭示了BAM1是此过程中小干扰RNA（siRNA）和微小RNA（miRNA）运动的重要调控因子，而双生病毒编码的C4蛋白是它们进行胞间传递的抑制子。包含BAM1的蛋白复合体的其他组分也已被鉴定出来。.

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