Induction of the activity of glycolytic enzymes correlates with enhanced hydrolysis of sucrose in the cytosol of transgenic potato tubers

The aim of this work was to define the metabolic factors which regulate the respiratory pathways in trangenic potato tubers. We previously found that respiration is enhanced in transgenic tubers which express a yeast invertas e and a glucokinase from Zymomonas mobilis. In this study we investigated g lycolysis in three further transgenic potato lines with profound changes in the mobilization of sucrose. We studied antisense ADPglucose pyrophosphory lase lines which are characterized by a reduction in starch accumulation an d a significant build up of sucrose and related metabolic intermediates. We also report the generation of two novel double transgenic lines where the yeast invertase is expressed specifically in tubers of the ADPglucose pyrop hosphorylase antisense line, targeted to either the cytosol or apopolast. W e evaluated whether the localization of sucrose cleavage had an impact on t he glycolytic induction, and assessed if invertase expression in the high-s ucrose background had any further effects on glycolysis. We found that indu ction of the glycolytic enzymes only occurs when the invertase is targeted to the cytosol, and that the extent of this induction was comparable in the wild type and antisenseADPglucose pyrophosphorylase backgrounds. We conclu de that the signal regulating glycolysis is directly linked to cytosolic su crose hydrolysis.