title: Starch synthase 4 is essential for coordination of starch granule formation with chloroplast division during Arabidopsis leaf expansion.
abstract: Arabidopsis thaliana mutants lacking the SS4 isoform of starch synthase have strongly reduced numbers of starch granules per chloroplast, suggesting that SS4 is necessary for the normal generation of starch granules. To establish whether it plays a direct role in this process, we investigated the circumstances in which granules are formed in ss4 mutants. Starch granule numbers and distribution and the accumulation of starch synthase substrates and products were investigated during ss4 leaf development, and in ss4 mutants carrying mutations or transgenes that affect starch turnover or chloroplast volume. We found that immature ss4 leaves have no starch granules, but accumulate high concentrations of the starch synthase substrate ADPglucose. Granule numbers are partially restored by elevating the capacity for glucan synthesis (via expression of bacterial glycogen synthase) or by increasing the volumes of individual chloroplasts (via introduction of arc mutations). However, these granules are abnormal in distribution, size and shape. SS4 is an essential component of a mechanism that coordinates granule formation with chloroplast division during leaf expansion and determines the abundance and the flattened, discoid shape of leaf starch granules.
authors: John Innes Centre, Norwich Research Park, Norwich, NR4 7UH, UK.
authors: Matilda
authors: M
authors: Crumpton-Taylor
authors: Marilyn
authors: M
authors: Pike
authors: Kuan-Jen
authors: KJ
authors: Lu
authors: Christopher M
authors: CM
authors: Hylton
authors: Regina
authors: R
authors: Feil
authors: Simona
authors: S
authors: Eicke
authors: John E
authors: JE
authors: Lunn
authors: Samuel C
authors: SC
authors: Zeeman
authors: Alison M
authors: AM
authors: Smith
mesh_terms: D000245:Adenosine Diphosphate Glucose / Q000378:metabolism; D060054:Agrobacterium / Q000201:enzymology; D017360:Arabidopsis / Q000201:enzymology* / Q000254:growth & development*; D029681:Arabidopsis Proteins; D002736:Chloroplasts / Q000378:metabolism*; D005936:Glucans / Q000378:metabolism; D006006:Glycogen Synthase / Q000378:metabolism; D006579:Heterozygote; D007527:Isoenzymes / Q000378:metabolism; D055442:Metabolome; D009154:Mutation / Q000235:genetics; D053141:Organelle Size; D018515:Plant Leaves / Q000201:enzymology* / Q000254:growth & development*; D034622:RNA Interference; D012995:Solubility; D013213:Starch / Q000096:biosynthesis*; D013214:Starch Synthase / Q000378:metabolism*
chemical_list: D029681:Arabidopsis Proteins; D005936:Glucans; D007527:Isoenzymes; D000245:Adenosine Diphosphate Glucose; D013213:Starch; D006006:Glycogen Synthase; D013214:Starch Synthase; C520418:starch synthase IV, Arabidopsis
keywords: ADPglucose; Arabidopsis thaliana; chloroplast; leaf expansion; starch granule; starch synthase; starch synthesis
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