Table III. Effect of decreased fumarase activity on the metabolism of [U-14C]Glc by potato tubers.
Tuber discs were preincubated in 10 mm MES-KOH (pH 6.5) containing 2 mm Glc in the presence of 10 mm [U-14C]Glc (specific activity of 8.11 MBq mmol−1). Each sample was extracted with boiling ethanol, and the amount of radioactivity in each metabolic fraction was determined as described in “Materials and Methods.” Values are means ± se of six biological replicates. Boldface values were determined by Student’s t test to be significantly different from the wild type (P < 0.05).
| Variable | Wild Type | FL31 | FL34 | FL60 |
|---|---|---|---|---|
| Label incorporated (Bq) | ||||
| Total uptake | 318.22±23.14 | 335.02±26.98 | 391.07±36.51 | 332.45±20.71 |
| Total metabolized | 257.88±25.86 | 292.25±21.84 | 326.05±27.29 | 281.20±20.82 |
| Redistribution of radiolabel (% of total assimilated) | ||||
| CO2 evolution | 8.20±0.65 | 8.42±0.63 | 8.29±0.66 | 8.92±0.67 |
| Organic acids | 20.69±4.16 | 22.39±4.39 | 29.74±1.90 | 25.38±3.41 |
| Amino acids | 9.41±0.76 | 12.55±2.02 | 9.63±0.35 | 11.35±0.84 |
| Suc | 28.62±3.78 | 35.76±3.04 | 21.73±1.96 | 27.51±2.46 |
| Starch | 19.79±4.36 | 9.05±2.77 | 15.95±3.61 | 11.96±3.52 |
| Protein | 3.01±0.23 | 3.59±0.18 | 3.09±0.18 | 3.53±0.30 |
| Cell wall | 7.90±0.92 | 6.57±0.70 | 6.32±0.70 | 7.29±1.05 |
| Fru | 2.38±1.01 | 1.68±1.46 | 5.25±1.52 | 4.06±1.66 |
| Specific activity of hexose phosphates (Bq nmol−1) | 0.40±0.04 | 0.44±0.12 | 0.61±0.05 | 0.45±0.07 |
| Metabolic flux (nmol hexose equivalents g−1 fresh wt h−1) | ||||
| Starch synthesis | 217.94±68.30 | 137.39±48.53 | 146.87±43.79 | 140.98±48.37 |
| Suc synthesis | 245.42±39.73 | 545.17±136.00 | 176.98±12.93 | 359.60±134.36 |
| Respiration | 472.11±28.27 | 627.73±106.49 | 425.62±40.07 | 556.38±118.06 |
| Cell wall synthesis | 77.18±8.55 | 94.13±23.42 | 53.71±9.20 | 98.01±42.02 |