Hypoxia induced by FGF signalling disruption impairs moulting via insulin and neurohormonal regulation in Rhodnius prolixus

Insects tracheal system undergoes dynamic changes during growth to meet increasing oxygen demands, which are crucial for processes like moulting. Studies in model organisms, such as Drosophila melanogaster, have identified key genetic regulators of tracheal development, including components of the FGF signalling pathway - branchless (bnl) and breathless (btl). The present study centres on the role of FGFR and bnl in R. prolixus in tracheogenesis and moulting regulation. Here we identified R. prolixus FGF signalling pathway orthologs implicated in tracheogenesis, providing insight into their conserved function in regulating tracheal development in this species. Knockdowns of Rp-bnl and Rp-FGFR insects show disruptions in three major biological processes: tracheogenesis, moulting, and metabolic homeostasis. Gene expression analysis revealed that Rp-bnl and Rp-FGFR down-expression induces tissue hypoxia, alters the expression of critical moulting regulators, and modifies metabolic pathways, by affecting the expression of central metabolic factors involved in carbohydrate and lipid metabolism, such as Insuline-like peptide and Adipokinetic hormone. Our work provides the first characterisation of the Rp-bnl/FGFR pathway in R. prolixus. It shows its central role in coordinating tracheogenesis, developmental timing, and the regulation of metabolic pathways, providing new insights into the molecular mechanisms behind these interconnected developmental and physiological processes under hypoxic stress.