Mitochondrial genome recovery by ATFS-1 is essential for development following starvation

Abstract

Nutrient availability regulates the C. elegans life cycle as well as mitochondrial physiology. Food deprivation significantly reduces mitochondrial genome (mtDNA) number and leads to aging-related phenotypes. Here, we demonstrate that the bZIP protein ATFS-1, a mediator of the mitochondrial unfolded protein response (UPRmt), is required to promote growth and establish a functional germline following prolonged starvation. Surprisingly, we found that the recovery of mtDNA copy number and development following starvation required mitochondrial-localized ATFS-1 but not its nuclear transcription activity. Lastly, we found that the insulin-like receptor DAF-2, functions upstream of ATFS-1 to modulate mtDNA content. We demonstrate that reducing DAF-2 activity represses ATFS-1 nuclear function while causing an increase in mtDNA content partly mediated by mitochondrial-localized ATFS-1. Combined, our data indicate the importance of the UPRmt in recovering mitochondrial mass and suggests that atfs-1-dependent mtDNA replication precedes mitochondrial network expansion following starvation.