Zhou Qiu-Zhong, Fu Ping, Li Shu-Shang, Zhang Chang-Jiang, Yu Quan-You, Qiu Chuan-Zhen, Zhang Hong-Bo, Zhang Ze
Laboratory of Evolutionary and Functional Genomics, School of Life Sciences, Chongqing University, Chongqing, China.
Postdoctoral Station of Biomedical Engineering, Chongqing University, Chongqing, China.
Front Genet. 2020 Mar 27;11:225. doi: 10.3389/fgene.2020.00225. eCollection 2020.
Long-term domestication and selective breeding have increased the silk yield of the domestic silkworm () by several times the amount of the silk yield of its wild ancestor (). However, little is known about the molecular mechanisms behind the increase in silk yield during domestication. Based on dynamic patterns of functional divergence in the silk gland between domestic and wild silkworms, we found that at early and intermediate stages of silk gland development, the up-regulated genes of the domestic silkworm were mainly involved in DNA integration, nucleic acid binding, and transporter activity, which are related to the division and growth of cells. This has led to the posterior silk gland (PSG) of the domestic silkworm having significantly more cells ("factories" of fibroin protein synthesis) than that of the wild silkworm. At the late stage of silk gland development, the up-regulated genes in the domestic silkworm was enriched in protein processing and ribosome pathways, suggesting protein synthesis efficiency is greatly improved during silkworm domestication. While there was an increase in fibroin protein synthesis, the production of sericin protein was simultaneously reduced in the silk gland of the domestic silkworm. This reflects that domestic and wild silkworms have been under different selection pressures. Importantly, we found that the network co-expressed with the silk-coding genes of the domestic silkworm was larger than that of the wild silkworm. Furthermore, many more genes co-expressed with silk-coding genes in the domestic silkworm were subjected to artificial selection than those in the wild silkworm. Our results revealed that the increase of silk yield during silkworm domestication is involved in improvement of a biological system which includes not only expansion of "factories" (cells of PSG) of protein synthesis, but also a high expression of silk-coding genes and silk production-related genes such as biological energy, transport, and ribosome pathway genes.
长期的驯化和选择性育种使家蚕（Bombyx mori）的蚕丝产量提高到其野生祖先（Bombyx mandarina）蚕丝产量的数倍。然而，关于驯化过程中蚕丝产量增加背后的分子机制却知之甚少。基于家蚕和野蚕丝腺功能分化的动态模式，我们发现在家蚕丝腺发育的早期和中期，家蚕上调的基因主要参与DNA整合、核酸结合和转运活性，这些与细胞的分裂和生长有关。这导致家蚕的后部丝腺（PSG）比野蚕具有显著更多的细胞（丝素蛋白合成的“工厂”）。在家蚕丝腺发育的后期，家蚕上调的基因富集在蛋白质加工和核糖体途径中，这表明在蚕的驯化过程中蛋白质合成效率大大提高。在家蚕丝腺中，虽然丝素蛋白合成增加，但丝胶蛋白的产生同时减少。这反映出家蚕和野蚕受到了不同的选择压力。重要的是，我们发现与家蚕丝编码基因共表达的网络比野蚕的更大。此外，与家蚕丝编码基因共表达的基因中，受到人工选择的比野蚕的更多。我们的结果表明，蚕驯化过程中蚕丝产量的增加涉及到一个生物系统的改善，该系统不仅包括蛋白质合成“工厂”（PSG细胞）的扩张，还包括丝编码基因以及生物能量、运输和核糖体途径基因等与蚕丝生产相关基因的高表达。
