title: Regulatory properties of ADP glucose pyrophosphorylase are required for adjustment of leaf starch synthesis in different photoperiods.
abstract: Arabidopsis (Arabidopsis thaliana) leaves synthesize starch faster in short days than in long days, but the mechanism that adjusts the rate of starch synthesis to daylength is unknown. To understand this mechanism, we first investigated whether adjustment occurs in mutants lacking components of the circadian clock or clock output pathways. Most mutants adjusted starch synthesis to daylength, but adjustment was compromised in plants lacking the GIGANTEA or FLAVIN-BINDING, KELCH REPEAT, F BOX1 components of the photoperiod-signaling pathway involved in flowering. We then examined whether the properties of the starch synthesis enzyme adenosine 5'-diphosphate-glucose pyrophosphorylase (AGPase) are important for adjustment of starch synthesis to daylength. Modulation of AGPase activity is known to bring about short-term adjustments of photosynthate partitioning between starch and sucrose (Suc) synthesis. We found that adjustment of starch synthesis to daylength was compromised in plants expressing a deregulated bacterial AGPase in place of the endogenous AGPase and in plants containing mutant forms of the endogenous AGPase with altered allosteric regulatory properties. We suggest that the rate of starch synthesis is in part determined by growth rate at the end of the preceding night. If growth at night is low, as in short days, there is a delay before growth recovers during the next day, leading to accumulation of Suc and stimulation of starch synthesis via activation of AGPase. If growth at night is fast, photosynthate is used for growth at the start of the day, Suc does not accumulate, and starch synthesis is not up-regulated.
authors.affiliation: John Innes Centre, Norwich Research Park, Norwich NR4 7UH, United Kingdom (S.T.M., O.F., J.B., A.M.S.); and Max Planck Institute of Molecular Plant Physiology, 14476 Potsdam, Germany (A.F., N.K., B.E., R.F., R.S., J.E.L., M.S.).
authors.forename: Sam T
authors.initials: ST
authors.lastname: Mugford
authors.affiliation: John Innes Centre, Norwich Research Park, Norwich NR4 7UH, United Kingdom (S.T.M., O.F., J.B., A.M.S.); and Max Planck Institute of Molecular Plant Physiology, 14476 Potsdam, Germany (A.F., N.K., B.E., R.F., R.S., J.E.L., M.S.).
authors.forename: Olivier
authors.initials: O
authors.lastname: Fernandez
authors.affiliation: John Innes Centre, Norwich Research Park, Norwich NR4 7UH, United Kingdom (S.T.M., O.F., J.B., A.M.S.); and Max Planck Institute of Molecular Plant Physiology, 14476 Potsdam, Germany (A.F., N.K., B.E., R.F., R.S., J.E.L., M.S.).
authors.forename: Jemima
authors.initials: J
authors.lastname: Brinton
authors.affiliation: John Innes Centre, Norwich Research Park, Norwich NR4 7UH, United Kingdom (S.T.M., O.F., J.B., A.M.S.); and Max Planck Institute of Molecular Plant Physiology, 14476 Potsdam, Germany (A.F., N.K., B.E., R.F., R.S., J.E.L., M.S.).
authors.forename: Anna
authors.initials: A
authors.lastname: Flis
authors.affiliation: John Innes Centre, Norwich Research Park, Norwich NR4 7UH, United Kingdom (S.T.M., O.F., J.B., A.M.S.); and Max Planck Institute of Molecular Plant Physiology, 14476 Potsdam, Germany (A.F., N.K., B.E., R.F., R.S., J.E.L., M.S.).
authors.forename: Nicole
authors.initials: N
authors.lastname: Krohn
authors.affiliation: John Innes Centre, Norwich Research Park, Norwich NR4 7UH, United Kingdom (S.T.M., O.F., J.B., A.M.S.); and Max Planck Institute of Molecular Plant Physiology, 14476 Potsdam, Germany (A.F., N.K., B.E., R.F., R.S., J.E.L., M.S.).
authors.forename: Beatrice
authors.initials: B
authors.lastname: Encke
authors.affiliation: John Innes Centre, Norwich Research Park, Norwich NR4 7UH, United Kingdom (S.T.M., O.F., J.B., A.M.S.); and Max Planck Institute of Molecular Plant Physiology, 14476 Potsdam, Germany (A.F., N.K., B.E., R.F., R.S., J.E.L., M.S.).
authors.forename: Regina
authors.initials: R
authors.lastname: Feil
authors.affiliation: John Innes Centre, Norwich Research Park, Norwich NR4 7UH, United Kingdom (S.T.M., O.F., J.B., A.M.S.); and Max Planck Institute of Molecular Plant Physiology, 14476 Potsdam, Germany (A.F., N.K., B.E., R.F., R.S., J.E.L., M.S.).
authors.forename: Ronan
authors.initials: R
authors.lastname: Sulpice
authors.affiliation: John Innes Centre, Norwich Research Park, Norwich NR4 7UH, United Kingdom (S.T.M., O.F., J.B., A.M.S.); and Max Planck Institute of Molecular Plant Physiology, 14476 Potsdam, Germany (A.F., N.K., B.E., R.F., R.S., J.E.L., M.S.).
authors.forename: John E
authors.initials: JE
authors.lastname: Lunn
authors.affiliation: John Innes Centre, Norwich Research Park, Norwich NR4 7UH, United Kingdom (S.T.M., O.F., J.B., A.M.S.); and Max Planck Institute of Molecular Plant Physiology, 14476 Potsdam, Germany (A.F., N.K., B.E., R.F., R.S., J.E.L., M.S.).
authors.forename: Mark
authors.initials: M
authors.lastname: Stitt
authors.affiliation: John Innes Centre, Norwich Research Park, Norwich NR4 7UH, United Kingdom (S.T.M., O.F., J.B., A.M.S.); and Max Planck Institute of Molecular Plant Physiology, 14476 Potsdam, Germany (A.F., N.K., B.E., R.F., R.S., J.E.L., M.S.) alison.smith@jic.ac.uk.
authors.forename: Alison M
authors.initials: AM
authors.lastname: Smith
mesh_terms: D017360:Arabidopsis / Q000201:enzymology* / Q000235:genetics / Q000528:radiation effects; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism; D051599:Glucose-1-Phosphate Adenylyltransferase / Q000235:genetics / Q000378:metabolism*; D009154:Mutation; D017440:Photoperiod; D010788:Photosynthesis; D018515:Plant Leaves / Q000235:genetics / Q000378:metabolism / Q000528:radiation effects; D030821:Plants, Genetically Modified; D013213:Starch / Q000378:metabolism*; D013395:Sucrose / Q000378:metabolism
chemical_list: D029681:Arabidopsis Proteins; D013395:Sucrose; D013213:Starch; D051599:Glucose-1-Phosphate Adenylyltransferase