A number of long noncoding RNAs (lncRNAs) have been identified in silkworm, but little is known about their functions. Recent study showed that the let-7 miRNA cluster (contains let-7, miR-2795, and miR-100) was transcribed from the last exon of lncRNA lncR17454 in silkworm. To investigate the functional role of lncR17454, dsRNAs of lncR17454 were injected into the hemolymph of 1-d-old third-instar larvae of Bombyx mori, repression of lncR17454 led to molting arrestment during the larval-larval and larval-pupal transition of silkworm, which was consistent to the result as let-7 knockdown in other studies. The expression level of mature let-7, miR-100, and miR-2795 decreased 40%, 36%, and 40%, respectively, while the mRNA level of two predicted target genes of let-7, the Broad Complex isoform 2 (BR-C-Z2) and the BTB-Zinc finger transcription repression factor gene Abrupt (Ab), increased significantly after lncR17454 knockdown. In contrast, when adding the 20-Hydroxyecdysone (20E) to silkworm BmN4 cell lines, the expression level of lncR17454 and let-7 cluster all increased significantly, but the expression of Abrupt, the predicted target gene of let-7, was repressed. Dual-luciferase reporter assays confirmed Abrupt was the real target of let-7. Here we found that the lncRNA lncR17454 can play regulator roles in the metamorphosis of silkworm through let-7 miRNA cluster and the ecdysone signaling pathway, which will provide new clues for lepidopteran pest control.

中文翻译：

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长链非编码 RNA lncR17454 通过 let-7 miRNA 簇调控家蚕变态。

在家蚕中鉴定出许多长链非编码 RNA (lncRNA)，但对其功能知之甚少。最近的研究表明，let-7 miRNA 簇（包含 let-7、miR-2795 和 miR-100）是从家蚕 lncRNA lncR17454 的最后一个外显子转录而来的。为了研究lncR17454的功能作用，将lncR17454的dsRNAs注射到家蚕1日龄三龄幼虫的血淋巴中，抑制lncR17454导致家蚕幼虫-幼虫和幼虫-蛹过渡期间的蜕皮停滞，这与其他研究中 let-7 敲除的结果一致。成熟的let-7、miR-100和miR-2795的表达水平分别下降了40%、36%和40%，而let-7的两个预测靶基因的mRNA水平，Broad Complex 异构体 2 (BR-C-Z2) 和 BTB-锌指转录抑制因子基因 Abrupt (Ab) 在 lncR17454 敲低后显着增加。相比之下，在家蚕BmN4细胞系中加入20-羟基蜕皮激素（20E）后，lncR17454和let-7簇的表达水平均显着增加，但let-7的预测靶基因Abrupt的表达受到抑制。双荧光素酶报告基因检测证实 Abrupt 是 let-7 的真正目标。在这里我们发现lncRNA lncR17454可以通过let-7 miRNA簇和蜕皮素信号通路在蚕的变态中发挥调节作用，这将为鳞翅目害虫的防治提供新的线索。在家蚕BmN4细胞系中加入20-Hydroxyecdysone (20E)后，lncR17454和let-7簇的表达水平均显着增加，但let-7的预测靶基因Abrupt的表达受到抑制。双荧光素酶报告基因检测证实 Abrupt 是 let-7 的真正目标。在这里我们发现lncRNA lncR17454可以通过let-7 miRNA簇和蜕皮素信号通路在蚕的变态中发挥调节作用，这将为鳞翅目害虫的防治提供新的线索。在家蚕BmN4细胞系中加入20-Hydroxyecdysone (20E)后，lncR17454和let-7簇的表达水平均显着增加，但let-7的预测靶基因Abrupt的表达受到抑制。双荧光素酶报告基因检测证实 Abrupt 是 let-7 的真正目标。在这里我们发现lncRNA lncR17454可以通过let-7 miRNA簇和蜕皮素信号通路在蚕的变态中发挥调节作用，这将为鳞翅目害虫的防治提供新的线索。