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An extra-plastidial α-glucan, water dikinase from Arabidopsis phosphorylates amylopectin in vitro and is not necessary for transient starch degradation

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posted on 2023-05-18, 11:20 authored by Glaring, MA, Zygadlo, A, Thorneycroft, D, Schulz, A, Steven SmithSteven Smith, Blennow, A, Baunsgaard, L
Starch phosphorylation catalysed by the α-glucan, water dikinases (GWD) has profound effects on starch degradation in plants. The Arabidopsis thaliana genome encodes three isoforms of GWD, two of which are localized in the chloroplast and are involved in the degradation of transient starch. The third isoform, termed AtGWD2 (At4g24450), was heterologously expressed and purified and shown to have a substrate preference similar to potato GWD. Analyses of AtGWD2 null mutants did not reveal any differences in growth or starch and sugar levels, when compared to the wild type. Subcellular localization studies in Arabidopsis leaves and in vitro chloroplast import assays indicated that AtGWD2 was not targeted to the chloroplasts. The AtGWD2 promoter showed a highly restricted pattern of activity, both spatially and temporally. High activity was observed in the companion cells of the phloem, with expression appearing just before the onset of senescence. Taken together, these data indicate that, although AtGWD2 is capable of phosphorylating α-glucans in vitro, it is not directly involved in transient starch degradation.


Publication title

Journal of Experimental Botany










School of Natural Sciences


Oxford Univ Press

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Great Clarendon St, Oxford, England, Ox2 6Dp

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Copyright 2007 The Author. Licensed under Creative Commons Attribution-NonCommercial 2.0 UK: England & Wales (CC BY-NC 2.0 UK)

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  • Open

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Expanding knowledge in the biological sciences

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