Table II.
Metabolic fluxes in Arabidopsis cell cultures under standard and elevated levels of oxygen
Fluxes were determined by fitting labeling and biomass data to the model shown in Figure 5. Net fluxes are the optimum estimate ± sd as determined by EstimateStat. A negative value indicates that the direction of net flux is opposite to that assumed in the model (Fig. 5). Exchange fluxes (JXch) are given as the optimum estimate, with lower and upper asymmetric bounds corresponding to the optimum normalized [0,1] exchange flux ±1 sd (see legend to Fig. 6). Where the bounds of the normalized exchange flux lie outside the [0,1] range, an exchange flux of 0 (≤0) or infinity (∞,≥1) is given. Where no exchange flux is given, the value was constrained to zero in the fit. See Supplemental Table S4 for the complete flux solution. DH, Dehydrogenase.
| Flux Name | Description | Standard O2
|
Elevated O2
|
||
|---|---|---|---|---|---|
| Net Flux | Exchange Flux | Net Flux | Exchange Flux | ||
| mmol d−1 per flask | mmol d−1 per flask | ||||
| upt | Glc uptake | 1.322 ± 0.071 | 2.066 ± 0.077 | ||
| CO2 | CO2 output | 2.772 ± 0.349 | 4.498 ± 0.291 | ||
| Hexose/triose metabolism | |||||
| chex1 | Cytosolic phosphoglucoseisomerase | 0.010 ± 0.425 | 0.000 (0.000, ∞) | −0.481 ± 0.396 | 2.196 (1.770, 2.778) |
| chex2 | Cytosolic aldolase | −0.003 ± 0.425 | 0.000 (0.000, 0.429) | −0.494 ± 0.396 | 0.000 (0.000, 0.864) |
| chex3 | Cytosolic pyruvate kinase | 0.805 ± 0.070 | 1.330 ± 0.083 | ||
| cpex | Hexose phosphate uptake by plastid | 0.921 ± 0.448 | 0.755 (0.212, 2.184) | 1.893 ± 0.407 | 0.000 (0.000, 0.223) |
| phex1 | Plastidic aldolase | 0.752 ± 0.424 | 0.000 (0.000, 2.206) | 1.630 ± 0.401 | 0.000 (0.000, 2.389) |
| phex2 | Plastidic pyruvate kinase | 0.422 ± 0.050 | 0.622 ± 0.050 | ||
| cphex | Glyceraldehyde-3-P DH | 1.570 ± 0.084 | 2.380 ± 0.110 | ||
| ppp1 | Oxidative pentose phosphate pathway | 0.402 ± 0.200 | 0.599 ± 0.161 | ||
| Biomass accumulation | |||||
| hcellwall | Cell wall (hexose component) | 0.293 ± 0.031 | 0.466 ± 0.053 | ||
| pcellwall | Cell wall (pentose component) | 0.063 ± 0.007 | 0.101 ± 0.012 | ||
| starchOUT | Starch | 0.022 ± 0.010 | 0.044 ± 0.010 | ||
| lipidOUT | Acetyl-CoA in phospholipid | 0.275 ± 0.031 | 0.446 ± 0.047 | ||
| glycerolOUT | Glycerol in phospholipid | 0.003 ± 0.000 | 0.004 ± 0.000 | ||
| TCA cycle | |||||
| cmex | Pyruvate uptake by mitochondrion | 0.754 ± 0.069 | 1.205 ± 0.082 | ||
| tca1 | Mitochondrial pyruvate DH | 0.773 ± 0.068 | 1.205 ± 0.081 | ||
| tca2 | Citrate synthase | 0.773 ± 0.068 | 1.205 ± 0.081 | ||
| tca3 | Aconitase and isocitrate DH | 0.727 ± 0.067 | 1.185 ± 0.081 | ||
| tca4 | α-Ketoglutarate DH and succinate DH | 0.649 ± 0.066 | 0.003 (0.000, 0.019) | 1.050 ± 0.079 | 0.000 (0.000, 0.031) |
| tca5a+b | Fumarase and malate DH | 0.646 ± 0.066 | 99.000 (19.075, ∞) | 1.074 ± 0.080 | 99.000 (20.365, ∞) |
| Anaplerotic fluxes | |||||
| ana1 | PEPC/PEPCK | 0.286 ± 0.043 | 0.068 (0.033, 0.105) | 0.349 ± 0.048 | 0.149 (0.131, 0.167) |
| ana2 | Mitochondrial ME | 0.019 ± 0.014 | 0.000 ± 0.048 | ||
| ana3 | Plastidic ME | 0.000 ± 0.035 | 0.035 ± 0.007 | ||
| Amino acid and organic acid synthesis | |||||
| ala | Ala synthesis | 0.051 ± 0.007 | 0.125 ± 0.015 | ||
| asp | Asp synthesis | 0.102 ± 0.006 | 0.145 ± 0.011 | ||
| glu | Glu synthesis | 0.078 ± 0.005 | 0.134 ± 0.006 | ||
| scit | Citrate accumulation | 0.046 ± 0.005 | 0.021 ± 0.002 | ||
| smal | Malate accumulation | 0.039 ± 0.006 | 0.037 ± 0.004 | ||
| ssucc | Succinate accumulation | 0.019 ± 0.002 | 0.002 ± 0.000 | ||
| sfumOUT | Fumarate accumulation | 0.001 ± 0.000 | 0.000 ± 0.000 | ||