DISCUSSION
Two characteristics can be noted about the four plant types in this study. The relative amount of rubisco genes in a tissue can be compared to each other. Also, if the rubisco was regulated before or after transcription. To regulate a protein before translation, an organism can inhibit mRNA formation using transcription factors. A cell can also stop a formed mRNA from undergoing translation by stopping the protein’s function via dephosphorylation, increasing protease activity, protein blocking factors, etc. (Lodish, 2007). Rubisco is a protein found in chloroplast which is an organelle with a specific set of DNA. Proteins are made from DNA in a similar way to bacteria in which translation occurs just after nucleotides are placed on the mRNA. There is no processing of the mRNA before translation occurs. Therefore there is no time to regulate the gene after transcription and before translation.
To determine the relative amounts of rubisco proteins, a Western Blot can be performed. If protein is not present in the Western Blot, then regulation might occurring before transcription. To confirm that a rubisco gene does exist in the cell and just isn’t being expressed, a Real Time PCR can be run. The RT-PCR shows the relative amounts of rubisco genes (or chloroplast organelles) present in the plant tissues. The results in this study shows that papyrus (wet environment) and hibiscus (moderate environment) regulate rubisco after it has been transcribed. According to Figure 3, it appears that extremely little amounts of rubisco were present in the sample of mother-in-law’s tongue (dry environment) and gooseberry tissues (dry environment). There could have been error in the procedure of isolating proteins. In the SDS-PAGE (Figure 3), the mother-in-law’s tongue and gooseberry do not appear to have proteins present in the sample. Assuming no experimental errors occurred, these two arid plants most likely regulate their rubisco proteins before they are translated. These plants both undergo CAM metabolism which is most efficient and therefore best for dry environments. There may be a relationship between the CAM metabolic pathway and the level of regulation of rubisco relating to amount of CO2 needed and how many times it is fixed. The amount of CO2 needed relates to the amount of water needed. The CAM pathway seems to be most efficient in producing carbohydrates given the low availability of water. Since it is efficient, rubisco will not be as readily needed. Therefore, it is beneficial to regulate rubisco before it is transcribed in order to conserve energy.
On the other hand, the plants found in normal and wet environments, hibiscus and papyrus, respectively, are regulated after they are translated. This may also relate to the type of metabolism and the availability of water. Each undergo C4 metabolism which relatively uses a lot of energy. Since a lot of energy is needed, rubisco is needed more readily in order to produce this energy. Therefore, the plants in these wetter environments will regulate their rubisco after they have been made (Lodish, 2008). It would, of course, be beneficial to study more species of plants found in arid environments in order to further relate protein level of expression and metabolic mechanisms.
Water may also have an effect on the amount of rubisco genes found in the tissues of plants in varying arid environments. In this study, we looked at two plants from very arid environments as well as plants found in a moderately and an extremely wet environment. The gooseberry plant, found in very arid environments, had a significantly higher amount of the rubisco gene found in its leaf tissue than the hibiscus, mother-in-law’s tongue, and papyrus. Papyrus, which was the plant found in swampy areas, had the least amount of rubisco gene of the other three plants. Hibiscus, the moderately wet plant, had a slightly higher amount of rubisco gene than did the mother-in-law’s tongue. It seems that rubisco is needed in higher concentrations in plants that are in arid environments which supports previous studies (Iker, 2009; Lawlor, 2009). Rubisco is a protein that appears to be less reactive in dry environments. If it is less reactive, a plant would need more in order to maintain the amount of photosynthesis required for the plant to live. The results support the original hypothesis except that the mother-in-law’s tongue only had a moderate amount of rubisco gene. With its arid environment, a large amount of rubisco gene would be expected. This could be due to the specificity of the plant. It may not need as much energy as the other dry plant and therefore only needs a certain amount of rubisco. For example, most dry plants are in the cacti family while this one is not. There is always the possibility of experimental error in which DNA was degraded before it could be processed in the PCR. This study suggests that there is a relationship between rubisco and water availability. Further studies would be appropriate using more plant species and more varied environments to strengthen this claim.