Plastidial localization of a potato 'Nudix' hydrolase of ADP-glucose linked to starch biosynthesis.
Escherichia coli and potato (Solanum tuberosum) ADP-sugar pyrophosphatases (EcASPP and StASPP, respectively) are 'Nudix' hydrolases of the bacterial glycogen and starch precursor molecule, ADP-glucose (ADPG). We have previously shown that potato leaves expressing EcASPP either in the cytosol or in the chloroplast exhibited large reductions in the levels of starch, suggesting the occurrence of cytosolic and plastidial pools of ADPG linked to starch biosynthesis. In this work, we produced and characterized potato and Arabidopsis plants expressing EcASPP and StASPP fused with green fluorescent protein (GFP). Confocal fluorescence microscopy analyses of these plants confirmed that EcASPP-GFP has a cytosolic localization, whereas StASPP-GFP occurs in the plastid stroma. Both source leaves and potato tubers from EcASPP-GFP-expressing plants showed a large reduction of the levels of both ADPG and starch. In contrast, StASPP-GFP-expressing leaves and tubers exhibited reduced starch and normal ADPG contents when compared with control plants. With the exception of starch synthase in StASPP-GFP-expressing plants, no pleiotropic changes in maximum catalytic activities of enzymes closely linked to starch metabolism could be detected in EcASPP-GFP- and StASPP-GFP-expressing plants. The overall data (i) show that potato plants possess a plastidial ASPP that has access to ADPG linked to starch biosynthesis and (ii) are consistent with the occurrence of plastidic and cytosolic pools of ADPG linked to starch biosynthesis.
Muñoz
Francisco José
FJ
Instituto de Agrobiotecnología, Universidad Pública de Navarra/Consejo Superior de Investigaciones Científicas/Gobierno de Navarra, Mutiloako etorbidea zenbaki gabe, 31192 Mutiloabeti, Nafarroa, Spain.
Baroja-Fernández
Edurne
E
Ovecka
Miroslav
M
Li
Jun
J
Mitsui
Toshiaki
T
Sesma
María Teresa
MT
Montero
Manuel
M
Bahaji
Abdellatif
A
Ezquer
Ignacio
I
Pozueta-Romero
Javier
J
D000245:Adenosine Diphosphate Glucose / Q000378:metabolism*; D017360:Arabidopsis / Q000201:enzymology / Q000235:genetics; D050260:Carbohydrate Metabolism; D018506:Gene Expression Regulation, Plant; D017343:Genes, Plant; D049452:Green Fluorescent Proteins / Q000235:genetics / Q000378:metabolism; D018613:Microscopy, Confocal; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism*; D030821:Plants, Genetically Modified / Q000201:enzymology / Q000235:genetics; D018087:Plastids / Q000201:enzymology* / Q000235:genetics; D011755:Pyrophosphatases / Q000235:genetics / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D011198:Solanum tuberosum / Q000201:enzymology* / Q000235:genetics; D013213:Starch / Q000096:biosynthesis*; D014170:Transformation, Genetic; D000096964:Nudix Hydrolases
D000245:Adenosine Diphosphate Glucose; D049452:Green Fluorescent Proteins; D010940:Plant Proteins; D011755:Pyrophosphatases; D011993:Recombinant Fusion Proteins; D013213:Starch; D000096964:Nudix Hydrolases