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Abstract L-serine (Ser) and L-glycine (Gly) are critically important for the overall functioning of primary metabolism. We investigated the interaction of the phosphorylated pathway of Ser biosynthesis (PPSB) with the photorespiration-associated glycolate pathway of Ser biosynthesis (GPSB) using Arabidopsis thaliana PPSB-deficient lines, GPSB-deficient mutants, and crosses of PPSB with GPSB mutants. PPSB-deficient lines mainly showed retarded primary root growth. Mutation of the photorespiratory enzyme Ser-hydroxymethyltransferase 1 (SHMT1) in a PPSB-deficient background resumed primary root growth and induced a change in the plant metabolic pattern between roots and shoots. Grafting experiments demonstrated that metabolic changes in shoots were responsible for the changes in double mutant development. PPSB disruption led to a reduction in nitrogen (N) and sulfur (S) contents in shoots and a general transcriptional response to nutrient deficiency. Disruption of SHMT1 boosted the Gly flux out of the photorespiratory cycle, which increased the levels of the one-carbon (1C) metabolite 5,10-methylene-tetrahydrofolate and S-adenosylmethionine. Furthermore, disrupting SHMT1 reverted the transcriptional response to N and S deprivation and increased N and S contents in shoots of PPSB-deficient lines. Our work provides genetic evidence of the biological relevance of the Ser–Gly–1C metabolic network in N and S metabolism and in interorgan metabolic homeostasis.
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This content will become publicly available on September 1, 2026
Metabolic flux analysis in leaf metabolism quantifies the link between photorespiration and one carbon metabolism
Photorespiration is the second largest carbon flux in most leaves and is integrated into metabolism broadly including one-carbon (C1) metabolism. Photorespiratory intermediates such as serine and others may serve as sources of C1 units, but it is unclear to what degree this happens in vivo, whether altered photorespiration changes flux to C1 metabolism, and if so through which intermediates. To clarify these questions, we quantified carbon flux from photorespiration to C1 metabolism using 13CO2 labelling and isotopically non-stationary metabolic flux analysis in Arabidopsis thaliana under different O2 concentrations which modulate photorespiration. The results revealed that ~5.8% of assimilated carbon passes to C1 metabolism under ambient photorespiratory conditions, but this flux greatly decreases under limited photorespiration. Furthermore, the primary carbon flux from photorespiration to C1 metabolism is through serine. Our results provide fundamental insight into how photorespiration is integrated into C1 metabolism, with possible implications for C1 metabolic response to climate change.
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- PAR ID:
- 10639811
- Publisher / Repository:
- Nature publishing group
- Date Published:
- Journal Name:
- Nature Plants
- Volume:
- 11
- Issue:
- 9
- ISSN:
- 2055-0278
- Page Range / eLocation ID:
- 1877 to 1889
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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