Broad-complex transcription factor mediates opposing hormonal regulation of two phylogenetically distant arginine kinase genes in Tribolium castaneum

Abstract

AbstractThe phosphoarginine-arginine kinase shuttle system plays a critical role in maintaining insect cellular energy homeostasis. Insect molting and metamorphosis are coordinated by fluctuations of the ecdysteroid and juvenile hormone. However, the hormonal regulation of insect arginine kinases remain largely elusive. In this report, we comparatively characterized two arginine kinase genes,TcAK1andTcAK2, inTribolium castaneum. Functional analysis using RNAi showed thatTcAK1andTcAK2play similar roles in adult fertility and stress response. TcAK1 was detected in cytoplasm including mitochondria, whereas TcAK2 was detected in cytoplasm excluding mitochondria. Interestingly,TcAK1expression was negatively regulated by 20-hydroxyecdysone and positively by juvenile hormone, whereasTcAK2was regulated by the opposite pattern. RNAi, dual-luciferase reporter assays and electrophoretic mobility shift assay further revealed that the opposite hormonal regulation ofTcAK1andTcAK2was mediated by transcription factor Broad-Complex. Finally, relatively stable AK activities were observed during larval-pupal metamorphosis, which was generally consistent with the constant ATP levels. These results provide new insights into the mechanisms underlying the ATP homeostasis in insects by revealing opposite hormonal regulation of two phylogenetically distant arginine kinase genes.