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Leaf day respiration involves multiple carbon sources and depends on previous dark metabolism
  • +2
  • Guillaume Tcherkez,
  • Cyril Abadie,
  • Julie Lalande,
  • Corentin Dourmap,
  • Anis Limami
Guillaume Tcherkez
Institut de Recherche en Horticulture et Semences

Corresponding Author:[email protected]

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Cyril Abadie
Institut de Recherche en Horticulture et Semences
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Julie Lalande
Institut de Recherche en Horticulture et Semences
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Corentin Dourmap
Institut de Recherche en Horticulture et Semences
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Anis Limami
Institut de Recherche en Horticulture et Semences
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Abstract

Day respiration ( R d) is the metabolic, non-photorespiratory process by which illuminated leaves liberate CO 2 during photosynthesis. R d is used routinely in photosynthetic models and is thus critical for calculations. However, metabolic details associated with R d are poorly known, and this can be problematic to predict how R d changes with environmental conditions and relates to night respiration. It is often assumed that day respiratory CO 2 release just reflects ‘ordinary’ catabolism (glycolysis and Krebs ‘cycle’). Here, we carried out a pulse-chase experiment, whereby a 13CO 2 pulse in the light was followed by a chase period in darkness and then in the light. We took advantage of non-targeted, isotope-assisted metabolomics to determine non-‘ordinary’ metabolism, detect carbon remobilisation, and compare light and dark 13C utilisation. We found that several concurrent metabolic pathways (‘ordinary’ catabolism, oxidative pentose phosphates pathway, amino acid production, nucleotide biosynthesis, and secondary metabolism) took place in the light and participate in net CO 2 efflux associated with day respiration. Flux reconstruction from metabolomics leads to an underestimation of R d, further suggesting the contribution of a variety of CO 2-evolving processes. Also, the cornerstone of the Krebs ‘cycle’, citrate, is synthetised de novo from photosynthates mostly in darkness, and remobilised or synthesised from stored material in the light. Collectively, our data provides direct evidence that leaf day respiration ( i) involves several CO 2-producing reactions and ( ii) is fed by different carbon sources, including stored carbon disconnected from current photosynthates.
09 Oct 2023Submitted to Plant, Cell & Environment
09 Oct 2023Assigned to Editor
09 Oct 2023Submission Checks Completed
15 Oct 2023Review(s) Completed, Editorial Evaluation Pending
23 Oct 2023Reviewer(s) Assigned