M1BP RNAi during Drosophila flight myogenesis: Analyses at 64h APF stage

Oxidative metabolism is the predominant energy source for muscle contraction. How this is transcriptionally regulated during muscle development to accommodate different metabolic requirements and muscle types is largely unknown. We show that the formation of mitochondria cristae harbouring the respiratory chain is concomitant with a large-scale transcriptional upregulation of genes linked with oxidative phosphorylation (OXPHOS) during the middle of Drosophila flight muscle development. We further demonstrate using high-resolution imaging, transcriptomic and biochemical analyses that Motif-1-binding protein (M1BP) transcriptionally regulates the expression of genes encoding critical components for OXPHOS complex assembly and integrity. In the absence of M1BP, mitochondrial respiratory complexes are improperly assembled and aggregate in the mitochondrial matrix, triggering a strong protein quality control response. Together, this study provides the first insight into the transcriptional regulation of oxidative metabolism during Drosophila myogenesis and identifies M1BP as a novel player in this process. Overall design: Differential gene expression analyses of M1BP RNAi in dorsolongitudinal flight muscle in pupae at 64h APF