Fig. 7.

Schematic diagrams illustrating essential mitochondrial modifications during early development. (A) The resumption of mitochondrial biogenesis by the implantation stage appears to be facilitated not only by increased mitochondrial biogenesis and mtDNA replication but also by the skewed balance between fission and fusion. (B) Enhanced aerobic metabolism by the implantation stage, especially OXPHOS, leads to increased ROS production, which appears be the inducer of GSH biosynthesis. The apoptotic and survival signals in early embryos may be balanced by the GSH-based stress response.