Table II.
Subcellular distribution of metabolites in potato tubers
| Metabolite | % of Total Tissue Content
|
||
|---|---|---|---|
| Amyloplast | Cytosol | Vacuole | |
| Cluster A | 3.8 ± 1.9 | 1.3 ± 0.6 | 95.0 ± 2.5 |
| Cluster B | 16.5 ± 6.1 | 8.3 ± 3.7 | 75.3 ± 7.7 |
| Cluster C | 58.8 ± 9.3 | 39.3 ± 7.8 | 2.0 ± 1.7 |
| Cluster D | 46.0 ± 9.0 | 32.3 ± 11.7 | 21.7 ± 7.3 |
| Suc | 5.0 ± 3.3 | 17.7 ± 3.1 | 77.3 ± 0.7 |
| Glc | 8.7 ± 3.7 | 14.3 ± 5.9 | 77.0 ± 5.7 |
| Fru | 15.7 ± 6.7 | n.d. | 84.3 ± 6.7 |
| Pro | 11.3 ± 6.9 | 39.3 ± 6.2 | 49.3 ± 6.7 |
| Leu | 12.0 ± 5.7 | 35.7 ± 3.4 | 52.3 ± 3.0 |
| Iso-Leu | 12.7 ± 5.4 | 20.3 ± 8.6 | 67.0 ± 7.6 |
| Met | 12.3 ± 2.8 | 3.3 ± 2.7 | 84.3 ± 2.3 |
| Tyr | 18.3 ± 2.6 | 1.3 ± 1.1 | 80.3 ± 1.8 |
| Asn | 34.7 ± 6.0 | 1.7 ± 1.0 | 63.7 ± 5.5 |
| Gln | 19.5 ± 11.3 | 32.0 ± 18.5 | 48.5 ± 7.2 |
| Homo-Ser | 26.7 ± 8.0 | 5.3 ± 4.4 | 68.0 ± 3.7 |
| Trp | 37.0 ± 16.8 | n.d. | 63.0 ± 16.8 |
Developing tuber samples were taken from 10-week-old plants grown in 2-L pots in the greenhouse. The tissue was fractionated using a nonaqueous procedure. Metabolites in each fraction were measured in methanol extracts using GC-MS. Cluster analysis was performed on the percentage distribution in the fractions of the gradient. Cluster A, Quinate, Lys, isocitrate, fumarate, malate, Man, and citrate. Cluster B, Ala, Gly, Ser, Thr, Tyr, Phe, Val, 5-oxo-Pro, Orn, mannitol, inositol, shikimate, and succinate. Cluster C, Fru-6-P and Glu-6-P. Cluster D, Asp and Glu. The subcellular distributions were calculated by comparing the metabolite and marker enzyme distributions using a three-compartment calculation program. The results represent the means ± se of measurements on three different fractionations with different tuber samples. n.d., Not detected.