Plant and Cell Physiology Advance Access published online on September 18, 2008
Plant and Cell Physiology, doi:10.1093/pcp/pcn145
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Plastidial localization of a potato "Nudix" hydrolase of ADPglucose linked to starch biosynthesis
(1) Instituto de Agrobiotecnología, Universidad Pública de Navarra/Consejo Superior de Investigaciones Científicas/Gobierno de Navarra, Mutiloako etorbidea zenbaki gabe, 31192 Mutiloabeti, Nafarroa, Spain. (2) Institute of Botany, Slovak Academy of Sciences, Dubravska cesta 14, SK-84523 Bratislava, Slovakia. (3) Laboratories of Plant and Microbial Genome Control and Department of Applied Biological Chemistry, Niigata University, 2-8050 Ikarashi, Niigata 950-2181, Japan
Corresponding author: Prof. Javier Pozueta-Romero, Instituto de Agrobiotecnología, Universidad Pública de Navarra, Gobierno de Navarra and Consejo Superior de Investigaciones Científicas, Mutiloako etorbidea zenbaki gabe, 31192 Mutiloabeti, Nafarroa, Spain, E-mail: javier.pozueta{at}unavarra.es, Tel: (34) 948168009, FAX: (34) 948232191
| Abstract |
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Escherichia coli and potato (Solanum tuberosum) ADP-sugar pyrophosphatases (EcASPP and StASPP, respectively) are "Nudix" hydrolases of the bacterial glycogen and starch precursor molecule, the 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. By 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 (a) show that potato plants possess a plastidial ASPP that has access to ADPG linked to starch biosynthesis and (b) are consistent with the occurrence of plastidic and cytosolic pools of ADPG linked to starch biosynthesis.
Keywords: Carbohydrate metabolism - Solanum tuberosum - StASPP - stroma - stromule
F.J.M, E.B.F. and M.O. have equally contributed to this work.
(Received August 29, 2008; Accepted September 15, 2008)
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