HPLC-MS/MS analyses show that the near-starchless aps1 and pgm leaves accumulate wild type levels of ADPglucose: further evidence for the occurrence of important ADPglucose biosynthetic pathway(s) alternative to the pPGI-pPGM-AGP pathway
Date
2014Author
Version
Acceso abierto / Sarbide irekia
Type
Artículo / Artikulua
Version
Versión publicada / Argitaratu den bertsioa
Impact
|
10.1371/journal.pone.0104997
Abstract
In leaves, it is widely assumed that starch is the end-product of a metabolic pathway exclusively taking place in the
chloroplast that (a) involves plastidic phosphoglucomutase (pPGM), ADPglucose (ADPG) pyrophosphorylase (AGP) and
starch synthase (SS), and (b) is linked to the Calvin-Benson cycle by means of the plastidic phosphoglucose isomerase
(pPGI). This view also implies that AGP is the ...
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In leaves, it is widely assumed that starch is the end-product of a metabolic pathway exclusively taking place in the
chloroplast that (a) involves plastidic phosphoglucomutase (pPGM), ADPglucose (ADPG) pyrophosphorylase (AGP) and
starch synthase (SS), and (b) is linked to the Calvin-Benson cycle by means of the plastidic phosphoglucose isomerase
(pPGI). This view also implies that AGP is the sole enzyme producing the starch precursor molecule, ADPG. However,
mounting evidence has been compiled pointing to the occurrence of important sources, other than the pPGI-pPGM-AGP
pathway, of ADPG. To further explore this possibility, in this work two independent laboratories have carried out HPLC-MS/
MS analyses of ADPG content in leaves of the near-starchless pgm and aps1 mutants impaired in pPGM and AGP,
respectively, and in leaves of double aps1/pgm mutants grown under two different culture conditions. We also measured
the ADPG content in wild type (WT) and aps1 leaves expressing in the plastid two different ADPG cleaving enzymes, and in
aps1 leaves expressing in the plastid GlgC, a bacterial AGP. Furthermore, we measured the ADPG content in ss3/ss4/aps1
mutants impaired in starch granule initiation and chloroplastic ADPG synthesis. We found that, irrespective of their starch
contents, pgm and aps1 leaves, WT and aps1 leaves expressing in the plastid ADPG cleaving enzymes, and aps1 leaves
expressing in the plastid GlgC accumulate WT ADPG content. In clear contrast, ss3/ss4/aps1 leaves accumulated ca. 300 foldmore
ADPG than WT leaves. The overall data showed that, in Arabidopsis leaves, (a) there are important ADPG biosynthetic
pathways, other than the pPGI-pPGM-AGP pathway, (b) pPGM and AGP are not major determinants of intracellular ADPG
content, and (c) the contribution of the chloroplastic ADPG pool to the total ADPG pool is low. [--]
Subject
aps1 leaves,
pgm leaves,
ADP glucose,
pPGI-pPGM-AGP pathway
Publisher
Public Library of Science
Published in
Plos One, 9(8): e104997
Departament
IdAB – Instituto de Agrobiotecnología / Agrobioteknologiako Institutua
Publisher version
Sponsorship
This research was partially supported by the grants [BIO2010-18239] from the Comisión Interministerial de Ciencia y Tecnología and Fondo Europeo de Desarrollo Regional (Spain) and [IIM010491.RI1] from the Government of Navarra, and by Iden Biotechnology. This research was also supported by Scientific Research on Innovative Areas [22114507] and Grants-in-Aid for Scientific Research (B) [22380186] from the Ministry of Education, Culture, Sports, Science and Technology, Japan.
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Except where otherwise noted, this item's license is described as © 2014 Bahaji et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.