Ivashuta Sergey, Zhang Yuanji, Wiggins B Elizabeth, Ramaseshadri Partha, Segers Gerrit C, Johnson Steven, Meyer Steve E, Kerstetter Randy A, McNulty Brian C, Bolognesi Renata, Heck Gregory R
Chesterfield Village Research Center, Monsanto Company, Chesterfield, Missouri 63017, USA.
RNA. 2015 May;21(5):840-50. doi: 10.1261/rna.048116.114. Epub 2015 Mar 23.
Environmental RNAi (eRNAi) is a sequence-specific regulation of endogenous gene expression in a receptive organism by exogenous double-stranded RNA (dsRNA). Although demonstrated under artificial dietary conditions and via transgenic plant presentations in several herbivorous insects, the magnitude and consequence of exogenous dsRNA uptake and the role of eRNAi remains unknown under natural insect living conditions. Our analysis of coleopteran insects sensitive to eRNAi fed on wild-type plants revealed uptake of plant endogenous long dsRNAs, but not small RNAs. Subsequently, the dsRNAs were processed into 21 nt siRNAs by insects and accumulated in high quantities in insect cells. No accumulation of host plant-derived siRNAs was observed in lepidopteran larvae that are recalcitrant to eRNAi. Stability of ingested dsRNA in coleopteran larval gut followed by uptake and transport from the gut to distal tissues appeared to be enabling factors for eRNAi. Although a relatively large number of distinct coleopteran insect-processed plant-derived siRNAs had sequence complementarity to insect transcripts, the vast majority of the siRNAs were present in relatively low abundance, and RNA-seq analysis did not detect a significant effect of plant-derived siRNAs on insect transcriptome. In summary, we observed a broad genome-wide uptake of plant endogenous dsRNA and subsequent processing of ingested dsRNA into 21 nt siRNAs in eRNAi-sensitive insects under natural feeding conditions. In addition to dsRNA stability in gut lumen and uptake, dosage of siRNAs targeting a given insect transcript is likely an important factor in order to achieve measurable eRNAi-based regulation in eRNAi-competent insects that lack an apparent silencing amplification mechanism.
环境RNA干扰（eRNAi）是指外源性双链RNA（dsRNA）对受体生物体内源基因表达进行的序列特异性调控。尽管在人工饲养条件下以及通过在几种植食性昆虫中展示转基因植物已证实了这一现象，但在外源dsRNA摄取的程度和后果以及eRNAi在昆虫自然生活条件下的作用仍不清楚。我们对以野生型植物为食的对eRNAi敏感的鞘翅目昆虫进行分析，发现其摄取了植物内源性长dsRNA，但未摄取小RNA。随后，dsRNA被昆虫加工成21个核苷酸的小干扰RNA（siRNA），并在昆虫细胞中大量积累。在对eRNAi不敏感的鳞翅目幼虫中未观察到宿主植物来源的siRNA积累。鞘翅目幼虫肠道中摄入的dsRNA的稳定性，随后从肠道摄取并运输到远端组织，似乎是eRNAi的促成因素。尽管相对大量不同的鞘翅目昆虫加工的植物来源的siRNA与昆虫转录本具有序列互补性，但绝大多数siRNA的丰度相对较低，RNA测序分析未检测到植物来源的siRNA对昆虫转录组有显著影响。总之，我们观察到在自然取食条件下，对eRNAi敏感的昆虫广泛摄取植物内源性dsRNA，并随后将摄入的dsRNA加工成21个核苷酸的siRNA。除了dsRNA在肠腔中的稳定性和摄取外，靶向给定昆虫转录本的siRNA剂量可能是一个重要因素，以便在缺乏明显沉默扩增机制的对eRNAi有反应的昆虫中实现基于eRNAi的可测量调控。
