Effects of nitrate and ammonium on assimilation of nitric oxide by Heterosigma akashiwo

Author(s)Healey, Emily M.
Author(s)Flood, Stacie
Author(s)Bock, Patience K.
Author(s)Fulweiler, Robinson W.
Author(s)York, Joanna K.
Author(s)Coyne, Kathryn J.
Date Accessioned2023-05-31T14:24:27Z
Date Available2023-05-31T14:24:27Z
Publication Date2023-01-12
Description© The Author(s) 2023. This article was originally published in Scientific Reports. The version of record is available at: https://doi.org/10.1038/s41598-023-27692-3
AbstractThe harmful alga Heterosigma akashiwo possesses a hybrid nitrate reductase (NR) enzyme, NR2-2/2HbN, which has the potential to convert NO to nitrate for assimilation into biomass. In previous research, NR transcription in H. akashiwo was induced by nitrate while NR activity was inhibited by ammonium. Here, the capacity of H. akashiwo to use NO in the presence of nitrate and/or ammonium was investigated to understand the regulation of NO assimilation. Continuous cultures of H. akashiwo were acclimated to growth on nitrate, ammonium, or a mixture of both. Aliquots from these cultures were spiked with 15N-labeled NO. The expression of genes involved in nitrogen assimilation was evaluated, as well as nitrate reductase activity and assimilation of 15N-labeled nitrogen into algal biomass. Results showed that NO induced expression and activity of NR, and upregulated expression of GOGAT regardless of the presence of other inorganic nitrogen sources, while GS expression decreased over time. Furthermore, 15NO uptake and assimilation was significantly higher in cultures acclimated for growth on ammonium compared to cultures acclimated for growth on nitrate alone. Assimilation of NO may provide H. akashiwo with a competitive advantage in N-poor environments or areas with elevated NO.
SponsorThis project was funded by the National Oceanic and Atmospheric Administration (NOAA) Center for Sponsored Coastal Ocean Research (CSCOR) Ecology and Oceanography of Harmful Algal Blooms (ECOHAB) program (Grant # NA18NOS4780165 to K.J. Coyne, J. York and R. Fulweiler. ECOHAB contribution #1040).
CitationHealey, E.M., Flood, S., Bock, P.K. et al. Effects of nitrate and ammonium on assimilation of nitric oxide by Heterosigma akashiwo. Sci Rep 13, 621 (2023). https://doi.org/10.1038/s41598-023-27692-3
PublisherScientific Reports
TitleEffects of nitrate and ammonium on assimilation of nitric oxide by Heterosigma akashiwo
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