Spatiotemporal localization and activity of mitochondria regulate actomyosin contractility in Drosophila gastrulation

Mitochondrial dynamics are vital for embryogenesis, but their role in morphogenesis is largely unexplored. In this study, we elucidate the role of mitochondrial dynamics and function in regulating apical constriction at the ventral furrow in Drosophila gastrulation. We find that spatiotemporal redistribution of mitochondria from basal to apically constricting regions is coincident with Myosin II accumulation in ventral epithelial cells. This apical enrichment depends on intact microtubules and is regulated by Dorsal/NFkb signaling pathway. Embryos expressing mitochondrial fission protein, Drp1 mutants, contain larger, basally accumulated mitochondria, decreased apical constriction and ventral furrow defects. Transcriptomic and proteomic profiling of Drp1 mutants shows no change in Dorsal signaling, but an upregulation of antioxidant enzymes, decreased respiratory complexes, and reduced reactive oxygen species (ROS), confirming loss of mitochondrial activity and a reduced environment. Depleting mitochondrial SOD2 in Drp1 mutant embryos restores levels of antioxidant proteins and increases ROS, leading to an oxidized environment. These embryos also show rescue in apical mitochondrial migration and Myosin II accumulation, thereby enabling proper ventral furrow formation. Our study reveals the functional importance of localized mitochondrial dynamics, regulated by the Dorsal signaling pathway, and mitochondrial activity in a spatiotemporal manner for apical constriction during gastrulation.