Abstract The fall armyworm Spodoptera frugiperda (Lepidoptera: Noctuidae) is a polyphagous pest with 353 plant species as its hosts, including maize, sorghum, cotton, and rice. Azadirachtin is one of the most effective botanical insecticides. The effect of azadirachtin against S. frugiperda remains to be determined. Here we report strong growth inhibition of azadirachtin on S. frugiperda larvae under either 1.0 or 5.0 μg/g azadirachtin. To explore the relevant mechanisms, the larvae fed with normal artificial diet and with 1.0 μg/g azadirachtin exposure for 3 days were collected as samples for RNA-Seq. RNA-Seq on S. frugiperda larvae under different treatments identified a total of 24,153 unigenes, including 3494 novel genes, were identified. Among them, 1282 genes were affected by 1.0 μg/g azadirachtin exposure, with 672 up-regulated and 610 down-regulated. The impacted genes include 61 coding for detoxification enzymes (31 P450s, 7 GSTs, 11 CarEs, 7 UGTs and 5 ABC transporters), 31 for cuticle proteins, and several proteins involved in insect chitin and hormone biosynthesis. Our results indicated that azadirachtin could regulate the growth of S. frugiperda by affecting insect chitin and hormone biosynthesis pathway. The enhanced expression of detoxification enzymes might be related to detoxifying azadirachtin. These findings provided a foundation for further delineating the molecular mechanism of growth regulation induced by azadirachtin in S. frugiperda larvae.

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基于RNA-seq鉴定草地贪夜蛾幼虫印楝素响应基因

摘要 秋粘虫草地贪夜蛾（鳞翅目：夜蛾科）是一种多食性害虫，寄主有玉米、高粱、棉花、水稻等353种植物。印楝素是最有效的植物杀虫剂之一。印楝素对草地贪夜蛾的作用仍有待确定。在这里，我们报告了印楝素在 1.0 或 5.0 μg/g 印楝素下对草地贪夜蛾幼虫的强烈生长抑制作用。为了探索相关机制，收集用正常人工饲料喂养并暴露 1.0 μg/g 印楝素 3 天的幼虫作为 RNA-Seq 的样本。不同处理下草地贪夜蛾幼虫的 RNA-Seq 共鉴定出 24,153 个 unigenes，包括 3494 个新基因。其中，1282个基因受到1.0 μg/g印楝素暴露的影响，672 个上调，610 个下调。受影响的基因包括 61 个编码解毒酶的基因（31 个 P450、7 个 GST、11 个 CarE、7 个 UGT 和 5 个 ABC 转运蛋白）、31 个用于角质层蛋白的基因以及几种参与昆虫几丁质和激素生物合成的蛋白质。我们的研究结果表明印楝素可以通过影响昆虫几丁质和激素生物合成途径来调节草地贪夜蛾的生长。解毒酶表达增强可能与印楝素解毒有关。这些发现为进一步阐明印楝素诱导草地贪夜蛾幼虫生长调节的分子机制提供了基础。以及参与昆虫几丁质和激素生物合成的几种蛋白质。我们的研究结果表明印楝素可以通过影响昆虫几丁质和激素生物合成途径来调节草地贪夜蛾的生长。解毒酶表达增强可能与印楝素解毒有关。这些发现为进一步阐明印楝素诱导草地贪夜蛾幼虫生长调节的分子机制提供了基础。以及参与昆虫几丁质和激素生物合成的几种蛋白质。我们的研究结果表明印楝素可以通过影响昆虫几丁质和激素生物合成途径来调节草地贪夜蛾的生长。解毒酶表达增强可能与印楝素解毒有关。这些发现为进一步阐明印楝素诱导草地贪夜蛾幼虫生长调节的分子机制提供了基础。