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Arabidopsis thaliana mutants lacking ADP-glucose pyrophosphorylase accumulate starch and wild-type ADP-Glucose content: Further evidence for the occurrence of important sources, other than ADP-glucose pyrophosphorylase, of ADP-glucose linked to leaf starch biosynthesis

AutorBahaji, Abdellatif ; Li, Jun ; Ovecka, Miroslav ; Ezquer, Ignacio ; Muñoz Pérez, Francisco José ; Baroja-Fernández, Edurne ; Romero, José M.; Almagro, Goizeder ; Montero, Manuel ; Hidalgo, Maite ; Sesma, María Teresa ; Pozueta Romero, Javier
Fecha de publicación2011
EditorOxford University Press
CitaciónPlant and Cell Physiology 52(7): 1162-1176 (2011)
ResumenIt is widely considered that ADP-glucose pyrophosphorylase (AGP) is the sole source of ADP-glucose linked to bacterial glycogen and plant starch biosynthesis. Genetic evidence that bacterial glycogen biosynthesis occurs solely by the AGP pathway has been obtained with glgC- AGP mutants. However, recent studies have shown that (i) these mutants can accumulate high levels of ADP-glucose and glycogen, and (ii) there are sources other than GlgC, of ADP-glucose linked to glycogen biosynthesis. In Arabidopsis, evidence showing that starch biosynthesis occurs solely by the AGP pathway has been obtained with the starchless adg1-1 and aps1 AGP mutants. However, mounting evidence has been compiled previewing the occurrence of more than one important ADP-glucose source in plants. In attempting to solve this 20-year-old controversy, in this work we carried out a judicious characterization of both adg1-1 and aps1. Both mutants accumulated wild-type (WT) ADP-glucose and approximately 2 of WT starch, as further confirmed by confocal fluorescence microscopic observation of iodine-stained leaves and of leaves expressing granule-bound starch synthase fused with GFP. Introduction of the sex1 mutation affecting starch breakdown into adg1-1 and aps1 increased the starch content to 8-10 of the WT starch. Furthermore, aps1 leaves exposed to microbial volatiles for 10 h accumulated approximately 60 of the WT starch. aps1 plants expressing the bacterial ADP-glucose hydrolase EcASPP in the plastid accumulated normal ADP-glucose and reduced starch when compared with aps1 plants, whereas aps1 plants expressing EcASPP in the cytosol showed reduced ADP-glucose and starch. Moreover, aps1 plants expressing bacterial AGP in the plastid accumulated WT starch and ADP-glucose. The overall data show that (i) there occur important source(s), other than AGP, of ADP-glucose linked to starch biosynthesis, and (ii) AGP is a major determinant of starch accumulation but not of intracellular ADP-glucose content in Arabidopsis. © 2011 The Author.
Identificadoresdoi: 10.1093/pcp/pcr067
issn: 0032-0781
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