Iron homeostasis and reproduction: Unveiling the Microbiome-Gut-Brain-Axis connection in the mosquito Anopheles culicifacies

Blood is an essential requirement for adult female mosquitoes to reproduce successfully. Communication between the Microbiome and Gut-Brain-Axis (mGBA) is crucial for maintaining organismal physiology during ovarian growth and development(1). Given the elevated iron levels in the blood, we investigated how mosquitoes maintain systemic iron homeostasis and reveals striking parallels to iron deficiency disorders in mammals. We demonstrate that the synergistic transcriptional regulation of Ferritin (Fer) and Transferrin (Trf) plays a crucial role in follicle development and egg maturation. Silencing both genes using RNA interference (RNAi) led to severe reproductive impairment, including ovarian arrest in 40% of females, a 50% reduction in oocyte numbers, and reduced first instar larval size. These e phenotypes correlate with increased reactive oxygen species (ROS) and altered serotonin (5-HT) receptor expression in the brain, likely driven by gut microbiota imbalance, and hence neurological signalling modulation due to disrupted iron metabolism. The unexpected discovery of a transcript encoding a novel hepcidin (AcHep) protein that was previously unknown in any insect or mosquito species, and surprisingly, its modest enrichment in the fat-body of the Fer+Trf knockdown mosquito, suggested that it may be involved in the maintenance of the systemic iron homeostasis, as in mammals. Summarily, our data provide the first molecular evidence in insects that iron metabolism disorders can impair mGBA communication and compromise reproductive outcomes, mirroring effects observed in mammalian iron deficiency. This study expands our understanding of irons systemic roles and opens new avenues for targeting mosquito reproduction in vector control strategies.