Table_1_A narrow host-range and lack of persistence in two non-target insect species of a bacterial symbiont exploited to deliver insecticidal RNAi in Western Flower Thrips.xlsx

IntroductionInsecticidal RNAi is a targeted pest insect population control measure. The specificity of insecticidal RNAi can theoretically be enhanced by using symbiotic bacteria with a narrow host range to deliver RNAi, an approach termed symbiont-mediated RNAi (SMR), a technology we have previously demonstrated in the globally-invasive pest species Western Flower Thrips (WFT).
MethodsHere we examine distribution of the two predominant bacterial symbionts of WFT, BFo1 and BFo2, among genome-sequenced insects. Moreover, we have challenged two non-target insect species with both bacterial species, namely the pollinating European bumblebee, Bombus terrestris, and an insect predator of WFT, the pirate bug Orius laevigatus.
ResultsOur data indicate a very limited distribution of either symbiont among insects other than WFT. Moreover, whereas BFo1 could establish itself in both bees and pirate bugs, albeit with no significant effects on insect fitness, BFo2 was unable to persist in either species.
DiscussionIn terms of biosafety, these data, together with its more specific growth requirements, vindicate the choice of BFo2 for delivery of RNAi and precision pest management of WFT.

引言
杀虫RNAi（insecticidal RNAi）是一种靶向性害虫种群防控手段。理论上，通过使用宿主范围狭窄的共生菌递送RNAi，可增强杀虫RNAi的特异性，该方法被称为共生菌介导RNAi（symbiont-mediated RNAi, SMR），我们此前已在全球性入侵害虫西花蓟马（Western Flower Thrips, WFT）中验证了该技术的可行性。

方法
本研究首先分析了西花蓟马的两种主要细菌共生菌BFo1与BFo2在已完成基因组测序昆虫中的分布情况。此外，我们分别利用这两种细菌菌株接种两种非靶标昆虫物种：授粉性昆虫欧洲熊蜂（Bombus terrestris），以及西花蓟马的捕食性天敌淡翅小花蝽（Orius laevigatus）。

结果
研究数据表明，除西花蓟马外，两种共生菌在其他昆虫类群中的分布范围均极为有限。进一步实验显示，BFo1可在熊蜂与淡翅小花蝽体内成功定殖，且未对昆虫的生存适合度造成显著负面影响；而BFo2无法在这两种昆虫体内持续存活。

讨论
从生物安全性维度来看，结合BFo2更为严苛的生长需求条件，本研究数据进一步佐证了选用BFo2作为RNAi递送载体，用于西花蓟马精准害虫防控的科学性与合理性。