The physiological functions of ABC transporters in Tribolium castaneum and their role in protecting insects from pesticides and their metabolites
Final Report Abstract
The red flour beetle, Tribolium castaneum, is a worldwide pest of stored grain products. In the lab, it is a powerful model insect for studying genetics, development and physiology of coleopteran species. The beetle is easy to rear and has a short generation time. This together with the fact that its genome was the first coleopteran genome to be fully sequenced and annotated make T. castaneum the most advanced genetic model among coleopteran species. Most notably, T. castaneum exhibits a very robust response to systemic RNA interference (RNAi), which allows specific gene silencing in all tissues and developmental stages. Finally, transposon-based and CRISPR/Cas-mediated techniques allow the creation of transgenic lines. Because T. castaneum develops resistance rapidly to many classes of insecticides, it is a potent test system for studying insecticides’ mode of action and resistance mechanisms. In this project, we studied the role of membrane transporters in molting and in detoxifying insecticides using T. castaneum as a model. We mainly focused on the roles of ATP Binding Cassette (ABC) transporters and Organic Anion Transport Proteins (OATP) in the transport of ecdysteroids and in the elimination of insecticides. Based on the finding that ABC and OATP genes are upregulated in response to insecticide treatment, it has been hypothesized that they are involved in insecticide elimination. However, identification of ABC and OATP transporters involved in insecticide detoxification remains challenging, because these transporters are known to transport a large range of chemically diverse molecules. In this project, we developed a comprehensive RNAi-based strategy for the identification of transporters involved in insecticide detoxification using T. castaneum as a model. We identified ABC and OATP transporters functioning in different tissues and contributing to the elimination of common insecticides such as Malathion (MAL) or diflubenzuron (DFB). The latter insecticide is thought to bind and inhibit the chitin synthase required for molting. In addition, we examined an ABC transporter which might be an alternative target of DFB. Similar to the insulin secretion in β-pancreatic cells, this ABC transporter may act as a regulatory subunit of a potassium channel and affect chitin synthesis via its dependency on calcium ions. We further showed that the efficiencies of MAL and DFB can be increased by either knocking-down the genes encoding the ABC transporters involved in their elimination or using ABC inhibitors known to impair their activities. These findings may be exploited to synergize the efficiency of already approved insecticides, a strategy that might be useful to overcome some problems related to insecticide resistance developed by many pest insects. Finally, we identified two transporters that are highly expressed in the larval fat body and mediate the transport of ecdysteroids. TcOATP4-C1 is evidently required for the uptake of the molting hormone precursor ecdysone (E) by fat body cells. Inside fat body cells E is converted into its active form, 20-hydroxyecdysone (20E), which in turn is secreted into the hemolymph by TcABCG-8A. Control of ecdysone conversion by the larval fat body could act as a mechanism linking the onset of the moulting process to the availability of energy reserves stored in the fat body.
Publications
- (2016) Chitin metabolic pathways in insects and their regulation: In Extracellular composite matrices in arthropods (Eds. Cohen E., Moussian B.), pp. 31-66. Springer Int. Publ. Switzerland
Muthukrishnan S., Merzendorfer H., Yasuyuki Arakane, Quing Yang
(See online at https://doi.org/10.1007/978-3-319-40740-1_2) - (2016). Multifaceted biological insights from a draft genome sequence of the tobacco hornworm moth, Manduca sexta. Insect Biochem Mol Biol 76, 118-147
Kanost, M.R., Arrese, E.L., Cao, X., Chen, Y.R., Chellapilla, S., Goldsmith, M.R., Grosse- Wilde, E., Heckel, D.G., Herndon, N., Jiang, H., et al.
(See online at https://doi.org/10.1016/j.ibmb.2016.07.005) - (2019). Chitin prevalence and function in bacteria, fungi and protists targeting chitin-containing organisms 1142, 19-59
Steinfeld, L., Vafaei, A., Rösner, J., and Merzendorfer, H.
(See online at https://doi.org/10.1007/978-981-13-7318-3_3) - (2020). Transcriptional plasticity of different ABC transporter genes from Tribolium castaneum contributes to diflubenzuron resistance. Insect Biochem Mol Biol 116, 103282
Rösner, J., and Merzendorfer, H.
(See online at https://doi.org/10.1016/j.ibmb.2019.103282) - (2020). Tribolium castaneum: a model for investigating the mode of action of insecticides and mechanisms of resistance. Curr Pharm Des
Rösner, J., Wellmeyer, B., and Merzendorfer, H.
(See online at https://doi.org/10.2174/1381612826666200513113140) - Functional analysis of ABCG and ABCH transporters from the red flour beetle, Tribolium castaneum. Pest Manag Sci
Rösner, J.
(See online at https://doi.org/10.1002/ps.6332) - (2021) Organic anion-transporting polypeptides are involved in the elimination of insecticides from the red flour beetle, Tribolium castaneum. J Pest Sci
Rösner, J., Tietmeyer, J. and Merzendorfer, H.
(See online at https://doi.org/10.1007/s10340-020-01317-4)
