State Key Laboratory of Resource Insects, Southwest University, Chongqing 400715, China.
Jinfeng Laboratory, Chongqing 401329, China.
Int J Mol Sci. 2023 Aug 10;24(16):12650. doi: 10.3390/ijms241612650.
The efficient production of silkworm silk is crucial to the silk industry. Silk protein synthesis is regulated by the juvenile hormone (JH) and 20-Hydroxyecdysone (20E). Therefore, the genetic regulation of silk production is a priority. JH binding protein (JHBP) transports JH from the hemolymph to target organs and cells and protects it. In a previous study, we identified 41 genes containing a JHBP domain in the genome. Only one JHBP gene, , is highly expressed in the posterior silk gland (PSG), and its function remains unknown. In the present study, we investigated the expression levels of and the major silk protein genes in the high-silk-producing practical strain () and the low-silk-producing local strain . We found that was more highly expressed in than in the strain, which is consistent with the expression pattern of fibroin genes. A subcellular localization assay indicated that is located in the cytoplasm. In vitro hormone induction experiments showed that was upregulated by juvenile hormone analogue (JHA) treatment. upregulation was significantly inhibited by the overexpression of (BmJHBPd2OE) at the cell level when induced by JHA. However, overexpression of in the PSG by transgenic methods led to the inhibition of silk fibroin gene expression, resulting in a reduction in silk yield. Further investigation showed that in the transgenic BmJHBPd2OE silkworm, the key transcription factor of the JH signaling pathway, Krüppel homolog 1 (Kr-h1), was inhibited, and 20E signaling pathway genes, such as broad complex (Brc), E74A, and ultraspiracle protein (USP), were upregulated. Our results indicate that plays an important role in the JH signaling pathway and is important for silk protein synthesis. Furthermore, our findings help to elucidate the mechanisms by which JH regulates silk protein synthesis.
家蚕丝绸的高效生产对丝绸工业至关重要。丝蛋白的合成受保幼激素（JH）和 20-羟基蜕皮酮（20E）的调节。因此，丝绸生产的遗传调控是当务之急。JH 结合蛋白（JHBP）将 JH 从血淋巴运送到靶器官和细胞并对其进行保护。在之前的研究中，我们在基因组中鉴定出 41 个含有 JHBP 结构域的基因。只有一个 JHBP 基因 ，在后部丝腺（PSG）中高度表达，但其功能尚不清楚。在本研究中，我们研究了高丝生产实用品系 （）和低丝生产本地品系 中 和主要丝蛋白基因的表达水平。我们发现 在 中的表达水平高于 品系，这与丝氨酸基因的表达模式一致。亚细胞定位试验表明 位于细胞质中。体外激素诱导实验表明，JH 类似物（JHA）处理可上调 的表达。在细胞水平上，当 JHA 诱导时，BmJHBPd2OE 的过表达显著抑制 的上调。然而，通过转基因方法在 PSG 中过表达 导致丝氨酸基因表达抑制，从而导致丝产量减少。进一步研究表明，在转基因 BmJHBPd2OE 家蚕中，JH 信号通路的关键转录因子 Krüppel 同源物 1（Kr-h1）受到抑制，20E 信号通路基因，如宽复合物（Brc）、E74A 和 ultraspiracle 蛋白（USP），上调。我们的结果表明 在 JH 信号通路中发挥重要作用，对丝蛋白合成很重要。此外，我们的发现有助于阐明 JH 调节丝蛋白合成的机制。
