Table 3.

Suc Feeding Leads to Increased AGPase Redox Activation, Increased Starch Synthesis, and Decreased Hexose Phosphate Levels in Discs from Growing Tubers

ParameterControl200 mM
 Suc
Suc content (μmol/g fresh wt)11.6 ± 0.422.2 ± 1.4
AGPase activation [Vsel/Vred] (%)33 ± 249 ± 3
Starch synthesis (% of total 14C absorbed)40 ± 359 ± 3
Hexose phosphate level (nmol/g fresh wt)225 ± 20148 ± 11
  • Tuber discs were cut from an intact growing tuber and incubated in buffer with and without 200 mM Suc for 2 h before they were either washed three times to analyze their Suc content or frozen immediately in liquid nitrogen to measure hexose phosphate levels and AGPase activity under selective (Vsel; −DTT) and reductive (Vred; +DTT) assay conditions. In parallel samples, 2 mM 14C-Glc kBq/μmol specific activity of 18.5) was provided to measure label incorporation into starch. Results are means ± se (n = 3 replicate measurements on different discs from the same tuber).