Multicopper oxidase-1 is required for iron homeostasis in Malpighian tubules of Helicoverpa armigera.

Multicopper oxidases (MCOs) are enzymes that contain 10 conserved histidine residues and 1 cysteine residue. MCO1 has been extensively investigated in the midgut because this MCO is implicated in ascorbate oxidation, iron homeostasis and immune responses. However, information regarding the action of MCO1 in Malpighian tubules is limited. In this study, Helicoverpa armigera was used as a model to investigate the function of MCO1 in Malpighian tubules. Sequence analysis results revealed that HaMCO1 exhibits typical MCO characteristics, with 10 histidine and 1 cysteine residues for copper ion binding. HaMCO1 was also found to be highly abundant in Malpighian tubules. Temporal expression patterns indicated that HaMCO1 is mainly expressed during larval molting stages. Hormone treatments [the molting hormone 20-hydroxyecdysone (20E) and juvenile hormone (JH)] revealed that 20E inhibits HaMCO1 transcript expression via its heterodimer receptor, which consists of ecdysone receptor (EcR) and ultraspiracle (USP), and that JH counteracts the action of 20E to activate HaMCO1 transcript expression via its intracellular receptor methoprene-tolerant (Met). HaMCO1 knockdown caused a significant decrease in iron accumulation and also significantly reduced transferrin and ferritin transcript expression. Therefore, HaMCO1 is coordinately regulated by 20E and JH and is required for iron homeostasis in Malpighian tubules.