Tatsuke Tsuneyuki, Tomita Shuichiro
Institute of Agrobiological Sciences, National Agriculture and Food Research Organization, 1-2 Owashi, Tsukuba, Ibaraki 305-8634, Japan.
J Insect Physiol. 2024 Oct;158:104695. doi: 10.1016/j.jinsphys.2024.104695. Epub 2024 Aug 16.
The silkworm (Bombyx mori) is a model organism for lepidopteran insects. It is an oligophagous insect that primarily feeds on mulberry leaves and has industrial use for the production of raw silk. The development of artificial diets has provided an alternative nutrient source for silkworms; however, one significant issue is that the production of cocoons is lower in silkworms reared on artificial diets compared with those reared on mulberry leaves. The differences in the silk gland in the late-stage fifth instar silkworm larvae, when silk synthesis is most active, between those raised on artificial diets and mulberry leaves, are unknown. In this study, we identified differences in the transcriptomes of the middle and posterior silk glands of fifth instar day five silkworm larvae reared on artificial diets compared with those reared on mulberry leaves using three strains: Daizo, Nichi01, and J137 × C146. We found that the silk-related genes fibrohexamerin (fhx), fibroin-light-chain (fibL), and fibroin-heavy-chain (fibH) in the middle silk gland, and ser1 in the posterior silk gland, were differentially expressed in a strain-dependent manner. In silkworms reared on artificial diets, fhx, fibL, and fibH in the middle silk gland were upregulated in Nichi01 and downregulated in J137 × C146, whereas ser1 in the posterior silk gland was upregulated in J137 × C146 compared with silkworms reared on mulberry leaves. Our results demonstrate that the diet and strain of silkworm larvae affect the expression of genes related to silk production in their silk glands during the late fifth instar stage.
家蚕（Bombyx mori）是鳞翅目昆虫的模式生物。它是一种寡食性昆虫，主要以桑叶为食，在生丝生产方面具有工业用途。人工饲料的开发为家蚕提供了一种替代营养来源；然而，一个重要问题是，与以桑叶饲养的家蚕相比，以人工饲料饲养的家蚕结茧量较低。在丝素合成最为活跃的五龄后期家蚕幼虫中，以人工饲料饲养和以桑叶饲养的家蚕之间丝腺的差异尚不清楚。在本研究中，我们使用三个品系：大造、日1和J137×C146，鉴定了以人工饲料饲养的五龄第5天家蚕幼虫与以桑叶饲养的家蚕幼虫中丝腺中部和后部转录组的差异。我们发现，丝腺中部与丝相关的基因纤维六聚体（fhx）、丝素轻链（fibL）和丝素重链（fibH），以及丝腺后部的ser1，以品系依赖的方式差异表达。在以人工饲料饲养的家蚕中，丝腺中部的fhx、fibL和fibH在日1中上调，而在J137×C146中下调，而与以桑叶饲养的家蚕相比，丝腺后部的ser1在J137×C146中上调。我们的结果表明，家蚕幼虫的饲料和品系会影响五龄后期丝腺中与丝生产相关基因的表达。
