Importance of isoforms of starch‐branching enzyme in determining the structure of starch in pea leaves

Tomlinson, Kim; Lloyd, J. R.; Smith, Alison M.

doi:10.1046/j.1365-313x.1997.11010031.x

Cited by 72 publications

(71 citation statements)

References 46 publications

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“…The shorter chains of amylopectin from Arabidopsis and pea leaf starch show a much more pronounced polymodal distribution of lengths than those of storage starches (Tomlinson et al, 1997;Zeeman et al, 1998a). We found that amylopectin from sex4 had increased numbers of chains between six and 11 Glc residues in length and fewer between 19 and 29 residues compared with wild-type amylopectin (Fig.…”

Section: Granule Size Shape and Structurementioning

confidence: 70%

Starch Synthesis in Arabidopsis. Granule Synthesis, Composition, and Structure

et al. 2002

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The aim of this work was to characterize starch synthesis, composition, and granule structure in Arabidopsis leaves. First, the potential role of starch-degrading enzymes during starch accumulation was investigated. To discover whether simultaneous synthesis and degradation of starch occurred during net accumulation, starch was labeled by supplying 14 CO 2 to intact, photosynthesizing plants. Release of this label from starch was monitored during a chase period in air, using different light intensities to vary the net rate of starch synthesis. No release of label was detected unless there was net degradation of starch during the chase. Similar experiments were performed on a mutant line (dbe1) that accumulates the soluble polysaccharide, phytoglycogen. Label was not released from phytoglycogen during the chase indicating that, even when in a soluble form, glucan is not appreciably degraded during accumulation. Second, the effect on starch composition of growth conditions and mutations causing starch accumulation was studied. An increase in starch content correlated with an increased amylose content of the starch and with an increase in the ratio of granule-bound starch synthase to soluble starch synthase activity. Third, the structural organization and morphology of Arabidopsis starch granules was studied. The starch granules were birefringent, indicating a radial organization of the polymers, and x-ray scatter analyses revealed that granules contained alternating crystalline and amorphous lamellae with a periodicity of 9 nm. Granules from the wild type and the high-starch mutant sex1 were flattened and discoid, whereas those of the high-starch mutant sex4 were larger and more rounded. These larger granules contained "growth rings" with a periodicity of 200 to 300 nm. We conclude that leaf starch is synthesized without appreciable turnover and comprises similar polymers and contains similar levels of molecular organization to storage starches, making Arabidopsis an excellent model system for studying granule biosynthesis.The Arabidopsis leaf is an excellent system in which to study starch granule biosynthesis for several reasons. First, starch accumulates in large amounts over a short period; up to one-half of the carbon assimilated through photosynthesis is stored as starch during the light period. As a consequence, it is possible to analyze the composition and structure of starch made over a period of a few hours by a defined set of enzymes. In contrast, starch synthesis in storage organs occurs over a long developmental period, during which there are usually considerable changes in the complement of starch-synthesizing enzymes (Smith and Martin, 1993; Burton et al., 1995) and in overall cellular conditions. Second, the rate of starch synthesis in leaves can be controlled by altering the irradiance and measured accurately by supplying 14 CO 2 . Third, our knowledge of the complete genome sequence of Arabidopsis and the availability of transposon and T-DNA-tagged populations enables specific knockout mutation...

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Section: Granule Size Shape and Structurementioning

confidence: 70%

Starch Synthesis in Arabidopsis. Granule Synthesis, Composition, and Structure

et al. 2002

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“…Absorbances were examined using 1 mg of starch granules with 0.2 mL of iodine solution in a total volume of 25 mL. amylose:amylopectin ratios, differ among tissues in the same plant (Sato, 1984;Tomlinson et al, 1997). The third step in starch synthesis, the formation of starch from ADPGlc, must therefore involve different enzyme isoforms and/or processes in different tissues.…”

Section: Discussionmentioning

confidence: 99%

Characterization of a Granule-Bound Starch Synthase Isoform Found in the Pericarp of Wheat

et al. 1998

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Waxy wheat (Triticum aestivum L.) lacks the waxy protein, which is also known as granule-bound starch synthase I (GBSSI). The starch granules of waxy wheat endosperm and pollen do not contain amylose and therefore stain red-brown with iodine. However, we observed that starch from pericarp tissue of waxy wheat stained blue-black and contained amylose. Significantly higher starch synthase activity was detected in pericarp starch granules than in endosperm starch granules. A granule-bound protein that differed from GBSSI in molecular mass and isoelectric point was detected in the pericarp starch granules but not in granules from endosperm. This protein was designated GBSSII. The N-terminal amino acid sequence of GBSSII, although not identical to wheat GBSSI, showed strong homology to waxy proteins or GBSSIs of cereals and potato, and contained the motif KTGGL, which is the putative substratebinding site of GBSSI of plants and of glycogen synthase of Escherichia coli. GBSSII cross-reacted specifically with antisera raised against potato and maize GBSSI. This study indicates that GBSSI and GBSSII are expressed in a tissue-specific manner in different organs, with GBSSII having an important function in amylose synthesis in the pericarp.

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“…Amylopectin and amylose were separated by selectively precipitating the amylose using thymol [20], and the amylopectin was analysed by HPLC. Two different HPLC systems were used to study the amylopectin.…”

Section: Production Of Amylopectin and Analysis By Hplcmentioning

confidence: 99%

“…The solution was digested at 37 mC for at least 4 h, passed through a 0.2 µm filter and 10 µl was injected on to a PA-100 column that was protected by a PA-100 guard column (Dionex). The elution conditions were as described previously [20].…”

Section: Production Of Amylopectin and Analysis By Hplcmentioning

confidence: 99%

Simultaneous antisense inhibition of two starch-synthase isoforms in potato tubers leads to accumulation of grossly modified amylopectin

Lloyd

LANDSCHÜTZE²,

Kossmann

1999

Biochemical Journal

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A chimaeric antisense construct was used to reduce the activities of the two major starch-synthase isoforms in potato tubers simultaneously. A range of reductions in total starch-synthase activities were found in the resulting transgenic plants, up to a maximum of 90 % inhibition. The reduction in starch-synthase activity had a profound effect on the starch granules, which became extremely distorted in appearance compared with the control lines. Analysis of the starch indicated that the amounts produced in the tubers, and the amylose content of the starch, were not affected by the reduction in activity. In order to understand why the starch granules were distorted, amylopectin was isolated and the constituent chain lengths analysed. This indicated that the amylopectin was very different to that of the

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Importance of isoforms of starch‐branching enzyme in determining the structure of starch in pea leaves

Cited by 72 publications

References 46 publications

Starch Synthesis in Arabidopsis. Granule Synthesis, Composition, and Structure

Starch Synthesis in Arabidopsis. Granule Synthesis, Composition, and Structure

Characterization of a Granule-Bound Starch Synthase Isoform Found in the Pericarp of Wheat

Simultaneous antisense inhibition of two starch-synthase isoforms in potato tubers leads to accumulation of grossly modified amylopectin

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