| PEPCK chromosome location and genotype | Soluble protein (g. g. fwt -1) | Total chlorophyll (mg. g. fwt-1) | Malate (mmol. g. fwt -1) |
| Wild type | 23.67 + 2.73 | 0.70 + 0.10 | 8.01 + 0.13 |
| Wild type (from mutant seed) | 19.33 + 2.33 | 1.01 + 0.10 | 10.79 + 0.58 * |
| Heterozygote 1 | 33.33 + 2.33 ** | 1.01 + 0.09 | 10.72 + 0.35 * |
| Heterozygote 2 | 23.67 + 2.19 | 0.95 + 0.11 | 10.08 + 0.39 * |
| Homozygote | 42.33 + 2.33 * ** | 1.00 + 0.11 | 7.52 + 0.30 ** |
* Denotes that P is significantly different at 5% level when compared to wild type.
** significantly different at 5% level when compared to wild type from mutant seed
The table above shows that there appears to be more soluble protein in homozygote rosette leaves compared to wild type. No difference in chlorophyll content. Less malate in wild type compared to both heterozygotes and wild type form mutant seed. Less malate in homozygote compared to wild type from mutant seed Graphs for the results can be seen in a power point presentation by clicking here Phenotypic differences of chromosome 4
- The homozygote stalk was significantly taller than that of the wild type plant, by around 20cm
- The siliques present on the homozygote plant were significantly shorter than those found on the wild type plant
- The homozygote had the smallest number of siliques present on the plant, the heterozygote had the most siliques
Differences in amino acids
In most sample plant tissues amino acids accumulate when PEPCK is absent. This can be seen when looking at the attached presentation. The concentration of amino acids is much larger in the homozygote samples of seeds and stalks, and a similar trend can be seen when looking at the total amino acid content of each plant genotype.Asparagine and glutamine are both important transport compounds in arabidopsis, they are also along with glutamic acid and aspartic acid important in the metabolic pathway of nitrogen. There is a trend in stalks which sees an increase in the amount of the four amino acids mentioned above form wild type to homozygote. It shows that amino acids are accumulating when PEPCK is knocked out. The heterozygote plants have a concentration that is in between the wild type and the homozygote, this suggests that only one allele is necasary, or that chomosome 5 may compensate for the lack of an allele. In seeds there is no such compensation effect as the heterozygote and the wild types have very similar concentrations, and the homozygote amino acid concentration being very high.
Future work PEPCK has been shown to be counteractive in the production of lysine. Lysine is an essential amino acid that is a key player in the production of various enzymes, hormones, and disease-fighting antibodies. Plants are generally a poor source of lysine (except for legumes). Maize seeds are an important food source for many people. To make them more nutritious it would be beneficial to prevent the action of PEPCK so as to increase the amount of lysine and overall amino acids in them.
The homozygote plant that lacked chromosome 4 PEPCK was much taller than the others. It is known that the amino acid tryptophan has a similar structure to that of Indole-3-Acetic Acid (IAA) an auxin hormone. IAA travels from cell to cell in the plant via special influx and efflux carriers. Tryptophan was found in much larger concentrations in the homozygote plant to the other two genotypes. It would be interesting to see if the concentration of auxins in the plants is altered when PEPCK is knocked out.
My project only looked at the knockout of either PEPCK 1 or PEPCK 2 on separate plants. Further experiments could investigate the effect of double knockouts on plant development and nitrogen metabolism.
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