The silkworm Bombyx mori is a valuable insect that synthesizes bulk amounts of fibroin protein in its posterior silk gland (PSG) and weaves these proteins into silk cocoons. The mechanism by which the fibroin protein is efficiently synthesized and precisely regulated is an important aspect that has yet to be fully elucidated. Here, we describe the regulatory characteristics of the promoters of fibroin protein-encoding genes, namely, fibroin heavy chain (fibH) and fibroin light chain (fibL), using an optimized Gal4/UAS binary system. We found that (1) UAS-linked enhanced green fluorescent protein (EGFP) was effectively activated in the PSGs of Gal4/UAS transgenic silkworms, and fluorescence was continuously detected in the PSGs after complete formation of silk glands. (2) In the PSGs of fourth- and fifth-instar larvae of transgenic silkworms driven by fibL-Gal4 (LG4) or fibH-Gal4 (HG4), EGFP mRNA was detected in only day-3 to day-6 fifth-instar larvae, while the EGFP protein could be detected at each day of both larval stages. (3) High-level expression of Gal4 and UAS-linked EGFP caused a delay in PSG degradation in Gal4/UAS transgenic silkworms. (4) At the early pupal stage, EGFP fluorescence was also detected in fat bodies of Gal4/UAS transgenic silkworms, indicating that the PSG-specific EGFP was transported into fat bodies during PSG degeneration; however, the underlying mechanism needs to be further elucidated. This study provides a modified Gal4/UAS system used for efficient tissue-specific expression of target genes in the PSGs of silkworms and provides new insights into the regulatory characteristics of the promoters of key fibroin protein-encoding genes.

中文翻译：

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使用改良的Gal4 / UAS系统洞察蚕丝蛋白基因启动子的调控特性。

家蚕是一种有价值的昆虫，可以在其后部丝腺（PSG）中合成大量的纤维蛋白蛋白，并将这些蛋白编织成蚕茧。有效地合成和精确调节血纤蛋白蛋白的机制是一个尚未充分阐明的重要方面。在这里，我们描述了使用优化的Gal4 / UAS二元系统编码纤维蛋白蛋白的基因，即纤维蛋白重链（fibH）和纤维蛋白轻链（fibL）的启动子的调控特性。我们发现（1）UAS连接的增强型绿色荧光蛋白（EGFP）在Gal4 / UAS转基因家蚕的PSG中被有效激活，并且在丝腺完全形成后在PSG中连续检测到荧光。（2）在由fibL-Gal4（LG4）或fibH-Gal4（HG4）驱动的转基因蚕的四龄和五龄幼虫的PSG中，仅在第3天至第6天的五龄幼虫中检测到EGFP mRNA。 ，而在两个幼虫阶段的每一天都可以检测到EGFP蛋白。（3）Gal4 / UAS转基因家蚕中Gal4和与UAS相连的EGFP的高表达导致PSG降解延迟。（4）在p早期，在Gal4 / UAS转基因家蚕的脂肪体中也检测到EGFP荧光，这表明PSG特异性EGFP在PSG变性期间转运到脂肪体中。但是，需要进一步阐明其基本机制。