Gu Shi-Hong
Department of Biology, National Museum of Natural Science, 1 Kuan-Chien Road, Taichung 404, Taiwan, ROC.
Comp Biochem Physiol A Mol Integr Physiol. 2025 Sep;307:111884. doi: 10.1016/j.cbpa.2025.111884. Epub 2025 Jun 2.
Activation of extracellular signal-regulated kinase (ERK) signaling is related to chilling-induced diapause termination in Bombyx mori eggs. However, the changes in expressions of upstream signaling and downstream target genes are not very clear. In the present study, I investigated temporal changes in gene expressions of the prothoracicotropic hormone (PTTH) and epidermal growth factor (Egf) signaling pathways, which are the major stimulators of ERK signaling in insect systems, during a long chilling period. My results showed that when chilling was conducted from 2 days post-oviposition, expressions of PTTH/Egf signaling pathway genes were maintained at relatively higher levels, compared to those kept at 25 °C. In eggs exposed to 5 °C from 15 days post-oviposition, expression of the PTTH gene had dramatically increased by day 45 after chilling. Egf signaling pathway genes, including spitz (spi), vein (vn), rhomboid (rho), and Egf receptor (Egfr), showed gene-specific increasing patterns during the chilling period. I further showed that expression of the pointed (an ERK target) gene was maintained at a relatively higher when chilling was conducted from 2 days post-oviposition. Expression of the pointed gene had dramatically increased by day 45 in eggs chilled beginning after 15 days post-oviposition. Additionally, dechorionation increased pointed gene expression. LY294002 (a specific phosphatidylinositol 3-kinase (PI3K) inhibitor) and U0126 (an ERK inhibitor) inhibited pointed gene expression in dechorionated eggs, indicating that both PI3K and ERK are involved in increased pointed gene expression. When eggs that had been kept at 5 °C for 30 days were transferred to 25 °C, expression levels of PTTH and pointed genes decreased after transfer, clearly indicating that continuous chilling for 45 days is necessary to sustain the higher expressions of these genes. To the best of my knowledge, this study presents the first comprehensive analysis of the transcriptional regulation of both upstream and downstream genes in the ERK signaling pathway during a chilling period, offering valuable insights into the mechanisms underlying chilling-induced diapause termination.
细胞外信号调节激酶（ERK）信号的激活与家蚕卵冷诱导滞育终止有关。然而，上游信号和下游靶基因表达的变化尚不清楚。在本研究中，我研究了在长时间低温处理期间，促前胸腺激素（PTTH）和表皮生长因子（Egf）信号通路基因表达的时间变化，这两条信号通路是昆虫系统中ERK信号的主要刺激因子。我的结果表明，产卵后2天开始进行低温处理时，与在25°C下保存的卵相比，PTTH/Egf信号通路基因的表达维持在相对较高的水平。在产卵后15天开始暴露于5°C的卵中，低温处理45天后PTTH基因的表达显著增加。Egf信号通路基因，包括spitz（spi）、vein（vn）、rhomboid（rho）和Egf受体（Egfr），在低温处理期间呈现基因特异性的增加模式。我进一步表明，产卵后2天开始进行低温处理时，pointed（一种ERK靶基因）基因的表达维持在相对较高的水平。在产卵后15天开始进行低温处理的卵中，pointed基因的表达在45天时显著增加。此外，去卵壳处理增加了pointed基因的表达。LY294002（一种特异性磷脂酰肌醇3激酶（PI3K）抑制剂）和U0126（一种ERK抑制剂）抑制了去卵壳处理的卵中pointed基因的表达，表明PI3K和ERK都参与了pointed基因表达的增加。当在5°C下保存30天的卵转移到25°C时，转移后PTTH和pointed基因的表达水平下降，这清楚地表明持续低温处理45天对于维持这些基因的高表达是必要的。据我所知，本研究首次全面分析了低温处理期间ERK信号通路上下游基因的转录调控情况，为冷诱导滞育终止的潜在机制提供了有价值的见解。
