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The priming of amylose synthesis in Arabidopsis leaves

journal contribution
posted on 2023-05-18, 11:25 authored by Zeeman, SC, Steven SmithSteven Smith, Smith, AM
We investigated the mechanism of amylose synthesis in Arabidopsis leaves using 14C-labeling techniques. First, we tested the hypothesis that short malto-oligosaccharides (MOS) may act as primers for granule-bound starch synthase I. We found increased amylose synthesis in isolated starch granules supplied with ADP[14C]glucose (ADP[14C]Glc) and MOS compared with granules supplied with ADP[14C]Glc but no MOS. Furthermore, using a MOS-accumulating mutant (dpe1), we found that more amylose was synthesized than in the wild type, correlating with the amount of MOS in vivo. When wild-type and mutant plants were tested in conditions where both lines had similar MOS contents, no difference in amylose synthesis was observed. We also tested the hypothesis that branches of amylopectin might serve as the primers for granule-bound starch synthase I. In this model, elongated branches of amylopectin are subsequently cleaved to form amylose. We conducted pulse-chase experiments, supplying a pulse of ADP[14C]Glc to isolated starch granules or14CO2 to intact plants, followed by a chase period in unlabeled substrate. We detected no transfer of label from the amylopectin fraction to the amylose fraction of starch either in isolated starch granules or in intact leaves, despite varying the time course of the experiments and using a mutant line (sex4) in which high-amylose starch is synthesized. We therefore find no evidence for amylopectin-primed amylose synthesis in Arabidopsis. We propose that MOS are the primers for amylose synthesis in Arabidopsis leaves.

History

Publication title

Plant Physiology

Volume

128

Pagination

1069-1076

ISSN

0032-0889

Department/School

School of Natural Sciences

Publisher

Amer Soc Plant Biologists

Place of publication

15501 Monona Drive, Rockville, USA, Md, 20855

Rights statement

Copyright 2002 American Society of Plant Biologists

Repository Status

  • Restricted

Socio-economic Objectives

Expanding knowledge in the biological sciences

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