The landscape of CMNGE during development across metazoan evolution. OXPHOS, mitochondrial ribosome, and TCA genes show elevated expression right after birth in mammals chicken (after hatching, apart from the liver), and in the lizard across tissues. This pattern is associated with elevated expression of regulators of mitochondrial biogenesis and with transition from hypoxia to normoxia. The frog and Drosophila show elevated CMNGE in association with the start of locomotion in the embryos. Blue arrows indicate downregulation; orange arrows, upregulation; and gray areas, elevated or reduced mitonuclear gene expression. (*) S. scroffa (pig) samples were available only from the liver. (**) D. rerio (zebrafish) and C. elegans did not show clear CMNGE.