Background: The transcriptional co-activators of the PGC-1 family have been proposed as master regulators of mitochondrial biogenesis. Drosophila has a single member of the family, Spargel (srl). Functional studies of srl allow PGC-1 role(s) in development and physiology to be elucidated without the confounding effects of tissue-specificity and redundancy. Spargel was previously shown to govern the expression of genes for mitochondrial functions in the adult fat body.
Results: Here we analysed the role of srl in early development. srl RNA was abundant in ovaries and early embryos but, upon cellularization, fell to low levels where it remained for the rest of development. Knockdown of srl in the female germline resulted in embryonic semilethality, with only ~10% of embryos able to complete development. Embryos from germline srl-knockdown mothers were predominantly small, with the majority suffering a catastrophic derangement of development marked by failure to form a uniform blatstoderm, irregular cell size and chaotic cell movements instead of orderly gastrulation. However, genes whose expression in early embryos depends on localized determinants were expressed normally. The abundance of representative mitochondrial proteins was not decreased in knockdown ovaries or embryos, and their mRNAs were generally increased rather than decreased.
Conclusions: We infer that srl has a more general role in early development, distinct from specifically promoting mitochondrial biogenesis.