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A critical role for disproportionating enzyme in starch breakdown is revealed by a knock-out mutation in Arabidopsis

Citation

Critchley, JH and Zeeman, SC and Takaha, T and Smith, AM and Smith, SM, A critical role for disproportionating enzyme in starch breakdown is revealed by a knock-out mutation in Arabidopsis, The Plant Journal, 26, (1) pp. 89-100. ISSN 0960-7412 (2001) [Refereed Article]

Copyright Statement

Copyright 2001 Blackwell Science Ltd

DOI: doi:10.1046/j.1365-313x.2001.01012.x

Abstract

Disproportionating enzyme (D-enzyme) is a plastidial α-1,4-glucanotransferase but its role in starch metabolism is unclear. Using a reverse genetics approach we have isolated a mutant of Arabidopsis thaliana in which the gene encoding this enzyme (DPE1) is disrupted by a T-DNA insertion. While D-enzyme activity is eliminated in the homozygous dpe11 mutant, changes in activities of other enzymes of starch metabolism are relatively small. During the diurnal cycle, the amount of leaf starch is higher in dpe11 than in wild type and the amylose to amylopectin ratio is increased, but amylopectin structure is unaltered. The amounts of starch synthesised and degraded are lower in dpe11 than in wild type. However, the lower amount of starch synthesised and the higher proportion of amylose are both eliminated when plants are completely de-starched by a period of prolonged darkness prior to the light period. During starch degradation, a large accumulation of malto-oligosaccharides occurs in dpe11 but not in wild type. These data show that D-enzyme is required for malto-oligosaccharide metabolism during starch degradation. The slower rate of starch degradation in dpe11 suggests that malto-oligosaccharides affect an enzyme that attacks the starch granule, or that D-enzyme itself can act directly on starch. The effects on starch synthesis and composition in dpe11 under normal diurnal conditions are probably a consequence of metabolism at the start of the light period, of the high levels of malto-oligosaccharides generated during the dark period. We conclude that the primary function of D-enzyme is in starch degradation.

Item Details

Item Type:Refereed Article
Keywords:starch metabolism, disproportionating enzyme, Arabidopsis thaliana, mutant, maltooligosaccharides.
Research Division:Biological Sciences
Research Group:Plant Biology
Research Field:Plant Physiology
Objective Division:Expanding Knowledge
Objective Group:Expanding Knowledge
Objective Field:Expanding Knowledge in the Biological Sciences
Author:Smith, SM (Professor Steven Smith)
ID Code:101556
Year Published:2001
Web of Science® Times Cited:156
Deposited By:Plant Science
Deposited On:2015-06-25
Last Modified:2015-09-21
Downloads:0

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