Regulation of Reproductive Functions by Host-Microbe Interactions

Introduction: We have previously found that the gut microbiome in flies participates in physiological regulation of oogenesis and host reproduction. How these gut bacteria can regulate germline functions in the ovary remains unclear. By integrating current information on host-microbiome interactions, we hypothesized that this regulation is mediated by contribution of bacteria to the mitochondrial function in the ovary.

Aim: To study the effect of gut bacteria on mitochondrial function in the ovary

Methods: Fly gut bacteria has been removed by egg dechorionation and sterilization. Mitochondrial abundance and gene expression has been tested by qPCR. Mitochondrial function has been evaluated by mitochondrial membrane potential staining.

Results: We found that removal of gut bacteria down-regulated the expression of key mitochondrial genes and reduced the levels of mitochondrial DNA (mtDNA) in the ovary. TMRE-based analysis of mitochondrial function in the ovary further revealed reduction in mitochondrial function in the follicle cells surrounding the egg chamber. Additionally, we found that the effect of bacterial removal on oogenesis is phenocopied by chemical inhibition of mitochondrial function. This effect was reversed upon removal of the inhibitor (similarly to the reversal of the oogenesis phenotype upon recolonization of the bacteria).

Conclusion: These findings support the idea of oogenesis regulation via bacterial modulation of mitochondrial activity in the follicle cells. The similarity to findings in other organisms (including mammals), supports a general theme of mitochondrial regulation of oogenesis. Uncovering the underlying mechanisms in Drosophila may therefore generate insights of broad relevance for other animals including human.