The beta-oxidation pathway is downregulated during diapause termination in Calanus copepods

© The Author(s), 2019. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Skottene, E., Tarrant, A. M., Olsen, A. J., Altin, D., Ostensen, M., Hansen, B. H., Choquet, M., Jenssen, B. M., & Olsen, R. E. R. The beta-oxidation pathway is downregulated during diapause termination in Calanus copepods. Scientific Reports, 9, (2019): 16686, doi: 10.1038/s41598-019-53032-5.Calanus copepods are keystone species in marine ecosystems, mainly due to their high lipid content, which is a nutritious food source for e.g. juvenile fish. Accumulated lipids are catabolized to meet energy requirements during dormancy (diapause), which occurs during the last copepodite stage (C5). The current knowledge of lipid degradation pathways during diapause termination is limited. We characterized changes in lipid fullness and generated transcriptional profiles in C5s during termination of diapause and progression towards adulthood. Lipid fullness of C5s declined linearly during developmental progression, but more β-oxidation genes were upregulated in early C5s compared to late C5s and adults. We identified four possible master regulators of energy metabolism, which all were generally upregulated in early C5s, compared to late C5s and adults. We discovered that one of two enzymes in the carnitine shuttle is absent from the calanoid copepod lineage. Based on the geographical location of the sampling site, the field-samples were initially presumed to consist of C. finmarchicus. However, the identification of C. glacialis in some samples underlines the need for performing molecular analyses to reliably identify Calanus species. Our findings contributes to a better understanding of molecular events occurring during diapause and diapause termination in calanoid copepods.The authors wish to thank Dept. of Biology at Norwegian University of Science and Technology (NTNU) for additional funding for Elise Skottene´s stay at Woods Hole Oceanographic Institution (WHOI), Christoffer H. Hilde for help in the field and in the lab, Siv Anina Etter, Øystein Leiknes, Sofia Soloperto and Clara Igisch for help with the field work, Justyna Świeżak and Signe D. Løvmo for experimental assistance, Hanny Rivera for help with bioinformatic analyses at WHOI. The RNA seq work was provided by the Genomics Core Facility (GCF). GCF is funded by the Faculty of Medicine and Health Sciences at NTNU and Central Norway Regional Health Authority. Ann M. Tarrant was funded by the National Science Foundation (Award Number OPP-1746087)