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Temporally regulated expression of a yeast invertase in potato tubers allows dissection of the complex metabolic phenotype obtained following its constitutive expression.

Abstract：

:The constitutive cytosolic expression of a yeast ( Saccharomyces cerevisiae ) invertase within potato ( Solanum tuberosum ) tubers has previously been documented to produce a dramatic metabolic phenotype in which glycolysis, respiration and amino acid synthesis are markedly enhanced at the cost of starch synthesis. These transgenic lines were further characterised by a massive cycle of sucrose degradation and resynthesis via sucrose-phosphate synthase. We have recently developed a B33 patatin driven alc gene construct allowing tight chemical control of gene expression following supply of acetaldehyde with minimal pleiotropic effects of the inducing agent on metabolism. This construct was used for chemical induction of the yeast invertase gene after 10-weeks growth to dissect the complex metabolic phenotype obtained after constitute expression. Inducible expression led to increased invertase activity within 24 h in well-defined areas within growing tubers. Although the sucrose levels were reduced, there was no effect on the levels of starch whilst levels of many amino acids decreased. Labelling experiments revealed that these lines exhibited increased rates of sucrose cycling, whereas rates of glycolysis and of starch synthesis were not substantially changed. From these results we conclude that sucrose cycling is stimulated in response to a short-term increase in the rate of sucrose mobilisation, providing evidence for a role of sucrose cycling as a buffering capacity that regulates the net rate of sucrose usage. In contrast, the dramatic increase in hexose-phosphate levels and the switch from starch synthesis to respiration seen on the constitutive expression of the invertase was not observed in the inducible lines, suggesting that this is the result of cumulative pleiotropic effects that occurred when the transgene was expressed throughout development.

journal_name

Plant Mol Biol

journal_title

Plant molecular biology

authors

Junker BH,Wuttke R,Tiessen A,Geigenberger P,Sonnewald U,Willmitzer L,Fernie AR

doi

10.1007/s11103-004-2525-8

subject

Has Abstract

pub_date

2004-09-01 00:00:00

pages

91-110

issue

eissn

0167-4412

issn

1573-5028

pii

DO00002525

journal_volume

pub_type

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Temporally regulated expression of a yeast invertase in potato tubers allows dissection of the complex metabolic phenotype obtained following its constitutive expression.