Division of Biology, Kansas State University, Manhattan, Kansas 66506, USA.
Genome Biol. 2008 Jan 17;9(1):R10. doi: 10.1186/gb-2008-9-1-r10.
RNA interference (RNAi) is a highly conserved cellular mechanism. In some organisms, such as Caenorhabditis elegans, the RNAi response can be transmitted systemically. Some insects also exhibit a systemic RNAi response. However, Drosophila, the leading insect model organism, does not show a robust systemic RNAi response, necessitating another model system to study the molecular mechanism of systemic RNAi in insects.
We used Tribolium, which exhibits robust systemic RNAi, as an alternative model system. We have identified the core RNAi genes, as well as genes potentially involved in systemic RNAi, from the Tribolium genome. Both phylogenetic and functional analyses suggest that Tribolium has a somewhat larger inventory of core component genes than Drosophila, perhaps allowing a more sensitive response to double-stranded RNA (dsRNA). We also identified three Tribolium homologs of C. elegans sid-1, which encodes a possible dsRNA channel. However, detailed sequence analysis has revealed that these Tribolium homologs share more identity with another C. elegans gene, tag-130. We analyzed tag-130 mutants, and found that this gene does not have a function in systemic RNAi in C. elegans. Likewise, the Tribolium sid-like genes do not seem to be required for systemic RNAi. These results suggest that insect sid-1-like genes have a different function than dsRNA uptake. Moreover, Tribolium lacks homologs of several genes important for RNAi in C. elegans.
Although both Tribolium and C. elegans show a robust systemic RNAi response, our genome-wide survey reveals significant differences between the RNAi mechanisms of these organisms. Thus, insects may use an alternative mechanism for the systemic RNAi response. Understanding this process would assist with rendering other insects amenable to systemic RNAi, and may influence pest control approaches.
RNA 干扰（RNAi）是一种高度保守的细胞机制。在某些生物中，如秀丽隐杆线虫，RNAi 反应可以系统传播。一些昆虫也表现出系统性 RNAi 反应。然而，作为主要昆虫模式生物的果蝇并不表现出强大的系统性 RNAi 反应，因此需要另一个模型系统来研究昆虫系统性 RNAi 的分子机制。
我们使用具有强大系统性 RNAi 的赤拟谷盗作为替代模型系统。我们已经从赤拟谷盗基因组中鉴定出核心 RNAi 基因以及可能参与系统性 RNAi 的基因。系统发育和功能分析表明，赤拟谷盗具有比果蝇稍多的核心成分基因，这可能使其对双链 RNA（dsRNA）的反应更为敏感。我们还鉴定出赤拟谷盗中三个秀丽隐杆线虫 sid-1 的同源物，后者编码可能的 dsRNA 通道。然而，详细的序列分析表明，这些赤拟谷盗同源物与秀丽隐杆线虫的另一个基因 tag-130 具有更高的同源性。我们分析了 tag-130 突变体，发现该基因在秀丽隐杆线虫的系统性 RNAi 中没有功能。同样，赤拟谷盗的 sid 样基因似乎也不是系统性 RNAi 所必需的。这些结果表明，昆虫 sid-1 样基因的功能不同于 dsRNA 摄取。此外，赤拟谷盗缺乏一些在秀丽隐杆线虫的 RNAi 中起重要作用的基因的同源物。
尽管赤拟谷盗和秀丽隐杆线虫都表现出强大的系统性 RNAi 反应，但我们的全基因组调查揭示了这两种生物的 RNAi 机制之间存在显著差异。因此，昆虫可能使用一种替代机制来进行系统性 RNAi。了解这一过程将有助于使其他昆虫易于接受系统性 RNAi，并可能影响害虫控制方法。
