High serine:glyoxylate aminotransferase activity lowers leaf daytime serine levels, inducing the phosphoserine pathway in Arabidopsis

Serine:glyoxylate aminotransferase (SGAT) converts glyoxylate and serine to glycine and hydroxypyruvate during photorespiration. Besides this, SGAT operates with several other substrates including asparagine. The impact of this enzymatic promiscuity on plant metabolism, particularly photorespiration...

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Bibliographic Details
Published in:Journal of experimental botany 2017-01, Vol.68 (3), p.643-656
Main Authors: Modde, Katharina, Timm, Stefan, Florian, Alexandra, Michl, Klaudia, Fernie, Alisdair R., Bauwe, Hermann
Format: Article
Language:English
Subjects:
Arabidopsis - genetics
Arabidopsis - growth & development
Arabidopsis - metabolism
Asparagine - metabolism
Cell Respiration
Metabolic Networks and Pathways
Phosphoserine - metabolism
Photosynthesis
Plant Leaves - growth & development
Plant Leaves - metabolism
Plant Proteins - genetics
Plant Proteins - metabolism
RESEARCH PAPER
Serine - metabolism
Transaminases - genetics
Transaminases - metabolism
Transcription, Genetic
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Summary:Serine:glyoxylate aminotransferase (SGAT) converts glyoxylate and serine to glycine and hydroxypyruvate during photorespiration. Besides this, SGAT operates with several other substrates including asparagine. The impact of this enzymatic promiscuity on plant metabolism, particularly photorespiration and serine biosynthesis, is poorly understood. We found that elevated SGAT activity causes surprisingly clear changes in metabolism and interferes with photosynthetic CO₂ uptake and biomass accumulation of Arabidopsis. The faster serine turnover during photorespiration progressively lowers day-time leaf serine contents and in turn induces the phosphoserine pathway. Transcriptional upregulation of this additional route of serine biosynthesis occurs already during the day but particularly at night, efficiently counteracting night-time serine depletion. Additionally, higher SGAT activity results in an increased use of asparagine as the external donor of amino groups to the photorespiratory pathway but does not alter leaf asparagine content at night. These results suggest leaf SGAT activity needs to be dynamically adjusted to ensure (i) variable flux through the photorespiratory pathway at a minimal consumption of asparagine and (ii) adequate serine levels for other cellular metabolism.
ISSN:0022-0957
1460-2431
DOI:10.1093/jxb/erw467