What question did this study set out to answer?

To identify and characterize the enzymatic activity of the Arabidopsis glucan, water dikinase AtGWD3 and evaluate its physiological function in transitory starch degradation.

January 11, 2005The Plant Journal

A novel isoform of glucan, water dikinase phosphorylates pre‐phosphorylated α‐glucans and is involved in starch degradation in Arabidopsis

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Authors

LBLone BaunsgaardUniversity of Copenhagen HLHenrik LütkenUniversity of Copenhagen RMRené MikkelsenDuPont (Denmark)

Discussion

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Implication

Experimental study demonstrates that AtGWD3 mediates C-3 starch phosphorylation in Arabidopsis, indicating an essential role for specific phosphate esters in transitory starch degradation.

Key Points

To identify and characterize the enzymatic activity of the Arabidopsis glucan, water dikinase AtGWD3 and evaluate its physiological function in transitory starch degradation.
Identified and cloned the AtGWD3 cDNA from Arabidopsis thaliana, followed by heterologous expression and biochemical purification of the recombinant protein to determine enzymatic activity.
Assayed substrate specificity using native and pre-phosphorylated amylopectin substrates with varied chain lengths.
Analyzed an Atgwd3 knockdown mutant to monitor diurnal leaf starch dynamics and measure C-3 glucosyl phosphorylation levels relative to wild-type plants.
Purified AtGWD3 preferentially phosphorylated the C-3 position of glucose residues on pre-phosphorylated amylopectin with long side chains.
The Atgwd3 mutant exhibited persistently elevated leaf starch content throughout the entire diurnal cycle compared to wild-type controls.
Starch from Atgwd3 mutant leaves displayed significantly decreased levels of C-3 phosphorylation, linking this modification to regular starch breakdown.

Cite This Study

Baunsgaard et al. (2005) studied this question.

synapsesocial.com/papers/6a77fb12656dd99464ec42ef https://doi.org/10.1111/j.1365-313x.2004.02322.x

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Implication

Experimental study demonstrates that AtGWD3 mediates C-3 starch phosphorylation in Arabidopsis, indicating an essential role for specific phosphate esters in transitory starch degradation.