Arif Muhammad Asif, Frank Wolfgang, Khraiwesh Basel
Department of Molecular Developmental Biology, Nijmegen Center for Molecular Life Sciences, 6500 HB Nijmegen, The Netherlands.
Int J Mol Sci. 2013 Jan 14;14(1):1516-40. doi: 10.3390/ijms14011516.
RNA interference (RNAi) is a mechanism that regulates genes by either transcriptional (TGS) or posttranscriptional gene silencing (PTGS), required for genome maintenance and proper development of an organism. Small non-coding RNAs are the key players in RNAi and have been intensively studied in eukaryotes. In plants, several classes of small RNAs with specific sizes and dedicated functions have evolved. The major classes of small RNAs include microRNAs (miRNAs) and small interfering RNAs (siRNAs), which differ in their biogenesis. miRNAs are synthesized from a short hairpin structure while siRNAs are derived from long double-stranded RNAs (dsRNA). Both miRNA and siRNAs control the expression of cognate target RNAs by binding to reverse complementary sequences mediating cleavage or translational inhibition of the target RNA. They also act on the DNA and cause epigenetic changes such as DNA methylation and histone modifications. In the last years, the analysis of plant RNAi pathways was extended to the bryophyte Physcomitrella patens, a non-flowering, non-vascular ancient land plant that diverged from the lineage of seed plants approximately 450 million years ago. Based on a number of characteristic features and its phylogenetic key position in land plant evolution P. patens emerged as a plant model species to address basic as well as applied topics in plant biology. Here we summarize the current knowledge on the role of RNAi in P. patens that shows functional overlap with RNAi pathways from seed plants, and also unique features specific to this species.
RNA干扰（RNAi）是一种通过转录基因沉默（TGS）或转录后基因沉默（PTGS）来调控基因的机制，是生物体基因组维持和正常发育所必需的。小非编码RNA是RNAi的关键参与者，并且已经在真核生物中得到了深入研究。在植物中，已经进化出了几类具有特定大小和特定功能的小RNA。小RNA的主要类别包括微小RNA（miRNA）和小干扰RNA（siRNA），它们在生物合成过程中有所不同。miRNA由短发夹结构合成，而siRNA则来源于长双链RNA（dsRNA）。miRNA和siRNA都通过与反向互补序列结合来控制同源靶RNA的表达，从而介导靶RNA的切割或翻译抑制。它们还作用于DNA并引起表观遗传变化，如DNA甲基化和组蛋白修饰。在过去几年中，植物RNAi途径的分析扩展到了苔藓植物小立碗藓，这是一种不开花、无维管束的古老陆地植物，大约在4.5亿年前从种子植物谱系中分化出来。基于一些特征及其在陆地植物进化中的系统发育关键地位，小立碗藓成为了一个植物模式物种，用于解决植物生物学中的基础和应用课题。在这里，我们总结了目前关于RNAi在小立碗藓中的作用的知识，它显示出与种子植物RNAi途径的功能重叠，以及该物种特有的独特特征。
