The Circadian Clock Gene Circuit Controls Protein and Phosphoprotein Rhythms in Arabidopsis thaliana

Johanna Krahmer*, Matthew Hindle, Laura K. Perby, Helle K. Mogensen, Tom H. Nielsen, Karen J. Halliday, Gerben van Ooijen, Thierry Le Bihan, Andrew J. Millar

*Corresponding author af dette arbejde

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Abstract

Twenty-four-hour, circadian rhythms control many eukaryotic mRNA levels, whereas the levels of their more stable proteins are not expected to reflect the RNA rhythms, emphasizing the need to test the circadian regulation of protein abundance and modification. Here we present circadian proteomic and phosphoproteomic time series from Arabidopsis thaliana plants under constant light conditions, estimating that just 0.4% of quantified proteins but a much larger proportion of quantified phospho-sites were rhythmic. Approximately half of the rhythmic phospho-sites were most phosphorylated at subjective dawn, a pattern we term the “phospho-dawn.” Members of the SnRK/CDPK family of protein kinases are candidate regulators. A CCA1-overexpressing line that disables the clock gene circuit lacked most circadian protein phosphorylation. However, the few phospho-sites that fluctuated despite CCA1-overexpression still tended to peak in abundance close to subjective dawn, suggesting that the canonical clock mechanism is necessary for most but perhaps not all protein phosphorylation rhythms. To test the potential functional relevance of our datasets, we conducted phosphomimetic experiments using the bifunctional enzyme fructose-6-phosphate-2-kinase/ phosphatase (F2KP), as an example. The rhythmic phosphorylation of diverse protein targets is controlled by the clock gene circuit, implicating posttranslational mechanisms in the transmission of circadian timing information in plants.

OriginalsprogEngelsk
Artikelnummer100172
TidsskriftMolecular and Cellular Proteomics
Vol/bind21
Udgave nummer1
Antal sider20
ISSN1535-9476
DOI
StatusUdgivet - 2022

Bibliografisk note

Funding Information:
Acknowledgments—We thank Lisa Imrie and Katalin Kis for expert technical support. This research was funded in whole, or in part, by the Wellcome Trust [096995/Z/11/Z]. For the purpose of open access, the authors have applied a CC BY public copyright licence to any author-accepted manuscript version arising from this submission. In addition, this work was supported by BBSRC awards (BB/D019621 and BB/J009423).

Publisher Copyright:
© 2021 THE AUTHORS.

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