Zhang Qiang, Sun Wei, Sun Bang-Yong, Xiao Yang, Zhang Ze
Laboratory of Evolutionary and Functional Genomics, School of Life Sciences, Chongqing University, Chongqing, 400044, China.
Sericulture & Agri-food Research Institute, Guangdong Academy of Agriculture Science, Guangzhou, 510640, China.
BMC Genomics. 2017 Sep 11;18(1):714. doi: 10.1186/s12864-017-4123-6.
Oogenesis in the domestic silkworm (Bombyx mori) is a complex process involving previtellogenesis, vitellogenesis and choriogenesis. During this process, follicles show drastic morphological and physiological changes. However, the genome-wide regulatory profiles of gene expression during oogenesis remain to be determined.
In this study, we obtained time-series transcriptome data and used these data to reveal the dynamic landscape of gene regulation during oogenesis. A total of 1932 genes were identified to be differentially expressed among different stages, most of which occurred during the transition from late vitellogenesis to early choriogenesis. Using weighted gene co-expression network analysis, we identified six stage-specific gene modules that correspond to multiple regulatory pathways. Strikingly, the biosynthesis pathway of the molting hormone 20-hydroxyecdysone (20E) was enriched in one of the modules. Further analysis showed that the ecdysteroid 20-hydroxylase gene (CYP314A1) of steroidgenesis genes was mainly expressed in previtellogenesis and early vitellogenesis. However, the 20E-inactivated genes, particularly the ecdysteroid 26-hydroxylase encoding gene (Cyp18a1), were highly expressed in late vitellogenesis. These distinct expression patterns between 20E synthesis and catabolism-related genes might ensure the rapid decline of the hormone titer at the transition point from vitellogenesis to choriogenesis. In addition, we compared landscapes of gene regulation between silkworm (Lepidoptera) and fruit fly (Diptera) oogeneses. Our results show that there is some consensus in the modules of gene co-expression during oogenesis in these insects.
The data presented in this study provide new insights into the regulatory mechanisms underlying oogenesis in insects with polytrophic meroistic ovaries. The results also provide clues for further investigating the roles of epigenetic reconfiguration and circadian rhythm in insect oogenesis.
家蚕（Bombyx mori）的卵子发生是一个复杂的过程，涉及卵黄发生前期、卵黄发生期和卵壳形成期。在此过程中，卵泡表现出剧烈的形态和生理变化。然而，卵子发生过程中基因表达的全基因组调控图谱仍有待确定。
在本研究中，我们获得了时间序列转录组数据，并利用这些数据揭示了卵子发生过程中基因调控的动态格局。共鉴定出1932个在不同阶段差异表达的基因，其中大部分发生在卵黄发生后期向卵壳形成前期的转变过程中。通过加权基因共表达网络分析，我们确定了六个阶段特异性基因模块，它们对应于多个调控途径。引人注目的是，蜕皮激素20-羟基蜕皮酮（20E）的生物合成途径在其中一个模块中富集。进一步分析表明，类固醇生成基因的蜕皮甾体20-羟化酶基因（CYP314A1）主要在卵黄发生前期和卵黄发生早期表达。然而，20E失活基因，特别是编码蜕皮甾体26-羟化酶的基因（Cyp18a1），在卵黄发生后期高度表达。20E合成和分解代谢相关基因之间这些不同的表达模式可能确保了在从卵黄发生向卵壳形成转变的关键点上激素滴度的快速下降。此外，我们比较了家蚕（鳞翅目）和果蝇（双翅目）卵子发生过程中的基因调控格局。我们的结果表明，这些昆虫卵子发生过程中基因共表达模块存在一些共识。
本研究提供的数据为多滋式meroistic卵巢昆虫卵子发生的调控机制提供了新的见解。这些结果也为进一步研究表观遗传重编程和昼夜节律在昆虫卵子发生中的作用提供了线索。
