A single miR390 targeting event is sufficient for triggering TAS3-tasiRNA biogenesis in Arabidopsis.
A single miR390 targeting event is sufficient for triggering TAS3-tasiRNA biogenesis in Arabidopsis.
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DOI：
10.1093/nar/gkx119
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发表时间：
2017-05-19
影响因子：
14.9
通讯作者：
Voinnet O
中科院分区：
文献类型：
--
作者：
de Felippes FF;Marchais A;Sarazin A;Oberlin S;Voinnet O
在植物中，tasiRNAs形成一类内源次生siRNAs，通过RNA依赖的RNA聚合酶-6(RDR6)作用于microRNA介导的非编码TAS RNAs的切割而产生。在拟南芥中，TAS1、TAS2和TAS4 tasiRNA的产生是通过22nt长的或/和不对称的miRNAs以ArgAerte-1(AGO1)依赖的方式介导的单一切割事件进行的。相比之下，TAS3的tasiRNA生产似乎遵循所谓的“两次打击”过程，在这种过程中，TAS3的双重靶向，特别是在21nt长的对称miR390的介导下，启动了AGO7依赖的tasiRNA的生产。有趣的是，TAS3 tasiRNA产生的特征在其他植物中不同，我们在这里表明，这些特征也使TAS3 tasiRNA在拟南芥中能够生物发生，事实上，单个miR390靶向事件就足以完成这一过程，这表明“一次点击”模型支持植物TAS转录本中二级siRNA生物发生的所有必要的雏形。进一步的结果表明，两次击打的配置可能增强了tasiRNA生产的保真度，从而提高了下游基因调控的准确性。最后，我们证明了“不可切割的一次点击”过程允许从TAS1和TAS3转录本中产生tasiRNA，这表明RDR6的招募不需要miRNA切割，也不需要miRNA切割，正如我们进一步证明的那样，SuPRRESSOR-of基因沉默-3的招募对tasiRNA的产生是必不可少的。
In plants, tasiRNAs form a class of endogenous secondary siRNAs produced through the action of RNA-DEPENDENT-RNA-POLYMERASE-6 (RDR6) upon microRNA-mediated cleavage of non-coding TAS RNAs. In Arabidopsis thaliana, TAS1, TAS2 and TAS4 tasiRNA production proceeds via a single cleavage event mediated by 22nt-long or/and asymmetric miRNAs in an ARGONAUTE-1 (AGO1)-dependent manner. By contrast, tasiRNA production from TAS3 seems to follow the so-called ‘two-hit’ process, where dual targeting of TAS3, specifically mediated by the 21nt-long, symmetric miR390, initiates AGO7-dependent tasiRNA production. Interestingly, features for TAS3 tasiRNA production differ in other plant species and we show here that such features also enable TAS3 tasiRNA biogenesis in Arabidopsis, and that a single miR390 targeting event is, in fact, sufficient for this process, suggesting that the ‘one-hit’ model underpins all the necessary rudiments of secondary siRNA biogenesis from plant TAS transcripts. Further results suggest that the two-hit configuration likely enhances the fidelity of tasiRNA production and, hence, the accuracy of downstream gene regulation. Finally, we show that a ‘non-cleavable one-hit’ process allows tasiRNA production from both TAS1 and TAS3 transcripts, indicating that RDR6 recruitment does not require miRNA cleavage, nor does the recruitment, as we further show, of SUPRRESSOR-OF-GENE-SILENCING-3, indispensable for tasiRNA generation.