Temporal Dynamics of Extracellular Signal-Regulated Kinase Phosphorylation and Associated Signaling Genes During...

This study investigated the temporal dynamics of extracellular signal-regulated kinase (ERK) phosphorylation, together with the expression profiles of its putative upstream ligands and downstream target genes, during embryonic development in Bombyx mori. The results revealed distinct ERK phosphorylation dynamics: significantly higher levels of phosphorylated ERK were observed between Days 1 and 6 after oviposition in developing eggs (non-diapause and HCl-treated eggs), whereas diapause eggs exhibited low levels. The temporal expression patterns of genes in the prothoracicotropic hormone (PTTH)/torso and epidermal growth factor (EGF) signaling pathways-spitz (spi), rhomboid (rho), and Egf receptor (Egfr)-did not differ between diapause and HCl-treated eggs. In contrast, the EGF pathway gene vein (vn) and genes in the transforming growth factor (TGF)-β signaling pathway-including the ligand myoglianin (myo) and its receptor babo-displayed distinct temporal expression patterns. Similarly, Jelly belly (Jeb)/anaplastic lymphoma kinase (Alk), fibroblast growth factor (Fgf)/Fgf receptor (Fgfr), neurotrophin (NT), and Toll-receptor ligands (spätzle family members (spz2, spz4, and spz5)) showed differential expression, with levels significantly elevated during the middle and late stages of embryonic development in HCl-treated eggs. Non-diapause and chilled eggs also exhibited increasing expression patterns of these genes, similar to those observed in HCl-treated eggs. Additionally, ERK target genes pointed and huckebein (hkb) showed higher and broader expression peaks in developing eggs compared to diapause eggs. This study provides a comprehensive analysis of the transcriptional regulation of upstream and downstream ERK signaling components during embryonic development and reveals new insights into the mechanisms underlying embryonic diapause.