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Plant Physiol, June 2000, Vol. 123, pp. 681-688
A Possible Role for Pyrophosphate in the Coordination of
Cytosolic and Plastidial Carbon Metabolism within the Potato
Tuber1
Eva M.
Farré,*
Peter
Geigenberger,
Lothar
Willmitzer, and
Richard N.
Trethewey2
Max-Planck-Institut für Molekulare Pflanzenphysiologie, Am
Mühlenberg 1, 14476 Golm, Germany (E.M.F., L.W., R.N.T.); and
Botanisches Institut, Universität Heidelberg, Im Neuenheimer Feld
360, 69120 Heidelberg, Germany (P.G.)
The early stages of tuber development are characterized by cell
division, high metabolic activity, and the predominance of invertase as
the sucrose (Suc) cleaving activity. However, during the subsequent
phase of starch accumulation the cleavage of Suc occurs primarily by
the action of Suc synthase. The mechanism that is responsible for this
switch in Suc cleaving activities is currently unknown. One striking
difference between the invertase and Suc synthase mediated cleavage of
Suc is the direct involvement of inorganic pyrophosphate (PPi) in the
latter case. There is presently no convincing explanation of how the
PPi required to support this process is generated in potato
(Solanum tuberosum) tubers. The major site of PPi
production in a maturing potato tubers is likely to be the reaction
catalyzed by ADP-glucose pyrophosphorylase, the first committed step of
starch biosynthesis in amyloplasts. We present data based on the
analysis of the PPi levels in various transgenic plants altered in
starch and Suc metabolism that support the hypothesis that PPi produced
in the plastid is used to support cytosolic Suc breakdown and that PPi
is an important coordinator of cytosolic and plastidial metabolism in
potato tubers.
1
This work was supported by grants from the
Max-Planck-Gesellschaft (to E.M.F. and R.N.T.).
2
Present address: Metanomics GmbH & Co. KGaA,
Tegeler Weg 33, 10589 Berlin, Germany.
*
Corresponding author; e-mail farre{at}mpimp-golm.mpg.de; fax
44-331-567-8250.
© 2000 American Society of Plant Physiologists
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