title: Subcellular pyrophosphate metabolism in developing tubers of potato (Solanum tuberosum).
abstract: PPi has previously been implicated specifically in the co-ordination of the sucrose-starch transition and in the broader context of its role as co-factor in heterotrophic plant metabolism. In order to assess the compartmentation of pyrophosphate (PPi) metabolism in the potato tuber we analysed the effect of expressing a bacterial pyrophosphatase in the amyloplast of wild type tubers or in the cytosol or amyloplast of invertase-expressing tubers. The second and third approaches were adopted since we have previously characterized the invertase expressing lines to both exhibit highly altered sucrose metabolism and to contain elevated levels of PPi (Farré et al. (2000a) Plant Physiol 123:681) and therefore this background rendered questions concerning the level of communication between the plastidic and cytosolic pyrophosphate pools relatively facile. In this study we observed that the increase in PPi in the invertase expressing lines was mainly confined to the cytosol. Accordingly, the expression of a bacterial pyrophosphatase in the plastid of either wild type or invertase-expressing tubers did not lead to a decrease in total PPi content. However, the expression of the heterologous pyrophosphatase in the cytosol of cytosolic invertase-expressing tubers led to strong metabolic changes. These results are discussed both with respect to our previous hypotheses and to current models of the compartmentation of potato tuber metabolism.
authors.affiliation: Max-Planck-Institut für Molekulare Pflanzenphysiologie, Am Mühlenberg 1, 14476 Golm, Germany. efarre@scripps.edu
authors.forename: Eva M
authors.initials: EM
authors.lastname: Farré
authors.forename: Susanne
authors.initials: S
authors.lastname: Tech
authors.forename: Richard N
authors.initials: RN
authors.lastname: Trethewey
authors.forename: Alisdair R
authors.initials: AR
authors.lastname: Fernie
authors.forename: Lothar
authors.initials: L
authors.lastname: Willmitzer
mesh_terms: D001426:Bacterial Proteins / Q000378:metabolism; D011756:Diphosphates / Q000378:metabolism*; D004926:Escherichia coli / Q000201:enzymology / Q000235:genetics; D029968:Escherichia coli Proteins / Q000235:genetics / Q000378:metabolism; D030821:Plants, Genetically Modified / Q000378:metabolism; D011755:Pyrophosphatases / Q000235:genetics / Q000378:metabolism; D011198:Solanum tuberosum / Q000254:growth & development* / Q000378:metabolism*; D013213:Starch / Q000378:metabolism; D013347:Subcellular Fractions / Q000378:metabolism; D013395:Sucrose / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; D011756:Diphosphates; D029968:Escherichia coli Proteins; D013395:Sucrose; D013213:Starch; D011755:Pyrophosphatases