Silk production in Bombyx mori L. is largely determined by the expression of genes encoding fibroin and sericin. Here, we examined the regulatory function of a microRNA (miRNA) on silk gene expression using the sericin‐1 gene (BmSer–1). First, we downloaded whole mature miRNAs of silkworm from miRBase and identified bmo‐miR‐2780a as a candidate miRNA for the regulation of BmSer‐1 expression. We used semi‐quantitative reverse transcription polymerase chain reaction (RT‐PCR) with stem‐loop primers to investigate the expression profile of bmo‐miR‐2780a and its predicted target gene BmSer‐1 in seven different tissues from 5th instar day‐3 larvae, including head, fat body, anterior silk gland (ASG), middle silk gland (MSG), posterior silk gland (PSG), middle gut, and hemolymph. Our results showed that bmo‐miR‐2780a was specifically expressed in the MSG and that the expression level of BmSer‐1 was significantly higher in the MSG than in other tissues. Recombinant plasmids carrying both pri‐mir‐2780a and Ser1–3′UTR were constructed and then used to cotransfect BmN cells. We further detected the effect of bmo‐miR‐2780a on Ser‐1 in vivo. These results showed that the target gene was significantly decreased by miR‐2780a compared with the control group (p < .05), thus indicating that bmo‐miR‐2780a might negatively regulate the expression of Ser‐1.

中文翻译：

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Bmo-miR-2780a调节家蚕的sericin-1基因的表达。

家蚕的丝产量在很大程度上取决于编码丝蛋白和丝胶蛋白的基因的表达。在这里，我们检查了使用sericin-1基因（BmSer-1）的microRNA（miRNA）对丝绸基因表达的调控功能。首先，我们从miRBase下载了完整的家蚕成熟miRNA，并将bmo‐miR‐2780a确定为调控BmSer‐1表达的候选miRNA 。我们使用半定量逆转录聚合酶链反应（RT-PCR）和茎环引物来研究bmo-miR-2780a及其预测靶基因BmSer-1的表达谱在第5龄第3天幼虫的七个不同组织中，包括头，脂肪体，前丝腺（ASG），中丝腺（MSG），后丝腺（PSG），中肠和血淋巴。我们的结果表明bmo‐miR‐2780a在味精中特异性表达，而BmSer‐ 1的表达水平在味精中明显高于其他组织。构建携带pri-mir-2780a和Ser1-3'UTR的重组质粒，然后将其共转染BmN细胞。我们进一步检测了bmo‐miR‐2780a在体内对Ser‐1的影响。这些结果表明，与对照组相比，miR-2780a显着降低了靶基因（p <  .05），表明bmo-miR-2780a可能会对Ser-1的表达产生负面影响。