小的非编码RNA(sRNA)作为精巧的分子出现,在真核生物中指导转录和转录后基因调控。作为植物中最重要的一类sRNAs,反式作用小干扰RNA(ta-siRNA)从微小RNA(miRNA)介导的TAS基因转录本的裂解开始,随后通过SILENCING3基因抑制(SGS3)稳定,并通过RNA依赖性RNA聚合酶6(RDR6)的作用转化为双链RNA(dsRNA)。一般来说,这些dsRNA由DICER-LIKE4(DCL4)加工并募集到ARGONAUTE1(AGO1)复合物中,以通过反式mRNA切割在转录后调节靶基因。在最近的一项研究中,我们发现了一个非经典的ta-siRNA通路:从miRNA引导的裂解位点开始,dsRNA被DCL1加工成21-ntsiRNA,与AGO4/6复合物结合,以顺式指导DNA甲基化。结合以前的结果,miRNA可以通过DCL3产生,加载到AGO4中并触发靶基因的表观遗传调控,这些发现表明了许多复杂的生物发生,效应子和作用途径存在于植物sRNAs王国中。
Small non-coding RNAs (sRNAs) emerge as exquisite molecules that are guided for transcriptional and posttranscriptional gene regulation in eukaryotes. As one class of most important sRNAs in plants, trans-acting small interfering RNAs (ta-siRNAs) initiate from microRNA (miRNA) - mediated cleavage of TAS gene transcripts and subsequently are stabilized by SUPPRESSOR OF GENE SILENCING3 (SGS3) and converted to double-stranded RNA (dsRNA) by the actions of RNA-DEPENDENT RNA POLYMERASE6 (RDR6). Generally, these dsRNAs are processed by DICER-LIKE4 (DCL4) and recruited into ARGONAUTE 1 (AGO1) complexes to posttranscriptionally regulate target genes by mRNA cleavage in trans. In a recent study, we discovered a non-canonical ta-siRNAs pathway: Starting from the miRNA-guided cleavage site, the dsRNAs are processed by DCL1 into 21-nt siRNAs, which associate with AGO4/6 complexes to direct DNA methylation in cis. Together with previous results that miRNAs can be produced by DCL3, loaded into AGO4 and trigger epigenetically regulation of target genes, these findings indicate much complex biogenesis, effector and action pathways exist in plant sRNAs kingdom.