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

Authors: ZHANG, NAN - Yangzhou University; JIANG, HENG - Yangzhou University; MENG, XIANGKUN - Yangzhou University; QIAN, KUN - Yangzhou University; LIU, YAPING - Yangzhou University; SONG, QISHENG - University Of Missouri; Stanley, David; WU, JINCAI - Yangzhou University; PARK, YOONSEONG - Kansas State University; WANG, JIANJUN - Yangzhou University

Submitted to: Communications Biology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/6/2020
Publication Date: 10/30/2020
Citation: Zhang, N., Jiang, H., Meng, X., Qian, K., Liu, Y., Song, Q., Stanley, D.W., Wu, J., Park, Y., Wang, J. 2020. Broad-complex transcription factor mediates opposing hormonal regulation of two phylogenetically distant arginine kinase genes in Tribolium castaneum. Communications Biology. 3. Article 631. https://doi.org/10.1038/s42003-020-01354-w.
DOI: https://doi.org/10.1038/s42003-020-01354-w

Interpretive Summary: Animals maintain energy levels within cells and in their overall bodies. Such maintenance is very important for insects because they go through very wide changes in energy needs on a moment-to-moment basis. For example, houseflies commonly go from virtually not moving (requiring very little energy) to full flight (very energy intensive) is less than one second. Particularly for pest insects, the mechanisms of how these energy levels are maintained are mostly unknown. Detailed information on these mechanisms have potential to reveal new gene targets that may be developed into new pest management technologies. In this paper we report on identification of two genes that specify proteins that act in maintaining near constant energy levels in flour beetles, insect pests of stored agricultural products. These proteins occur in all life stages and in all tissues we examined. Inhibiting the genes led to defective development. This work will contribute valuable new knowledge to scientists who work on developing new insect pest management technologies and ultimately benefit all consumers of agricultural products.

Technical Abstract: As an ATP buffering system, arginine kinase (AK) maintains ATP homeostasis in invertebrate, including insect, cells. Two groups of AK family genes have been revealed by bioinformatic analysis of several insect species. A more complete understanding of AK genes requires information on their functional divergence and the molecular mechanisms regulating their expression. Here, two full-length cDNAs, one encoding a typical group 1 insect AK (TcAK1) and another encoding a group 2 AK (TcAK2), were isolated from the red flour beetle, Tribolium castaneum. Analysis of transcript levels by qPCR and enzymatic activities of recombinant enzymes expressed in Escherichia coli indicate that TcAK1 is the dominant AK form in T. castaneum. Functional analysis using RNA interference (RNAi) showed that TcAK1 and TcAK2 play similar roles in adult fertility and stress response. Immunofluorescence staining and western blot showed that TcAK1 locates in cytoplasm including mitochondria, while TcAK2 occurs in cytoplasm excluding mitochondria. TcAK1 expression was negatively regulated by 20-hydroxyecdysone and positively by juvenile hormone, while TcAK2 was regulated in the opposite pattern. RNAi and dual luciferase reporter assays revealed that the opposite regulation of TcAK1 and TcAK2 is mediated by the insect-specific transcription factor Broad-Complex. Finally, relatively stable in vivo AK activities occurred during larval-pupal metamorphosis, which was generally consistent with the constant whole-insect ATP levels. Thus, our results provide new insights into the mechanisms underlying the ATP homeostasis in insects by revealing opposite hormonal regulation of two phylogenetically distant AK genes.