title: High serine:glyoxylate aminotransferase activity lowers leaf daytime serine levels, inducing the phosphoserine pathway in Arabidopsis.
abstract: 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.
authors.affiliation: University of Rostock, Plant Physiology Department, Albert-Einstein-Straße, Rostock, Germany.
authors.forename: Katharina
authors.initials: K
authors.lastname: Modde
authors.affiliation: University of Rostock, Plant Physiology Department, Albert-Einstein-Straße, Rostock, Germany.
authors.forename: Stefan
authors.initials: S
authors.lastname: Timm
authors.affiliation: Max Planck Institute of Molecular Plant Physiology, Am Mühlenberg, Golm, Germany.
authors.forename: Alexandra
authors.initials: A
authors.lastname: Florian
authors.affiliation: University of Rostock, Plant Physiology Department, Albert-Einstein-Straße, Rostock, Germany.
authors.forename: Klaudia
authors.initials: K
authors.lastname: Michl
authors.affiliation: Max Planck Institute of Molecular Plant Physiology, Am Mühlenberg, Golm, Germany.
authors.forename: Alisdair R
authors.initials: AR
authors.lastname: Fernie
authors.affiliation: University of Rostock, Plant Physiology Department, Albert-Einstein-Straße, Rostock, Germany.
authors.forename: Hermann
authors.initials: H
authors.lastname: Bauwe
mesh_terms: D017360:Arabidopsis / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism; D001216:Asparagine / Q000378:metabolism*; D019069:Cell Respiration; D053858:Metabolic Networks and Pathways; D010768:Phosphoserine / Q000378:metabolism; D010788:Photosynthesis; D018515:Plant Leaves / Q000254:growth & development / Q000378:metabolism; D010940:Plant Proteins / Q000235:genetics* / Q000378:metabolism; D012694:Serine / Q000378:metabolism*; D000637:Transaminases / Q000235:genetics* / Q000378:metabolism; D014158:Transcription, Genetic
chemical_list: D010940:Plant Proteins; D010768:Phosphoserine; D012694:Serine; D001216:Asparagine; D000637:Transaminases; C022636:serine-glyoxylate aminotransferase
keywords: Arabidopsis thaliana; phosphoserine pathway; photorespiration; serine; serine biosynthesis; serine:glyoxylate aminotransferase