Revision as of 20:40, 1 October 2024

pL2-Psr1

pL2-aadA-Psr1 (pL2-Psr1) is a combination of our two level 1 builds pL1-aadA (BBa_K5078004), and pL1 Psr1 (BBa_K5078003). The goal of this build was to see how well the Psr1 gene induced a phosphate (PO₄³⁻) starvation response in Chlamydomonas reinhardtii, before we inserted it into our final nutrient uptake plasmids (BBa_K5078009 and BBa_K5078010). Doing this allowed us to determine if the nitrogen half of our final plasmids affected the phosphate half. Additionally, it helped us determine if our PTC amiRNA (BBa_K5078007) helped or hindered Psr1. pL1-aadA was added to pL1-Psr1 in order to give C. reinhardtii spectinomycin resistance, which allowed for simple differentiation of transformed C. reinhardtii.

Figure 1. Plasmid diagram of pL2-aadA-Psr1 using Benchling for modeling.

Plasmid Verification

Successful transformation of pL2-Psr1 into host bacterium was determined by restriction digest with the restriction enzyme BsaI, with expected band lengths at 7259bp and 4635bp. Additionally, bacterial colonies should appear white in the presence of X-gal.

Figure 2. pL2-Psr1 diagnostic digest using BsaI on a 0.8% agarose gel. The restriction digest indicated that colonies 1, 2, 3, and 4 were successfully transformed.

Usage and Biology

Phosphate Uptake Experiments

To determine how well C. reinhardtii transformed with pL2-Psr1 took up PO₄³⁻ from its environment we performed several phosphate uptake assays with it, alongside two wild-type strains of C. reinhardtii 1690cc and 4039, which were acquired from Chlamy Collection (chlamycollection.org). These wild-type strains helped to confirm if pL2-Psr1 was affecting how C. reinhardtii took up PO₄³⁻.

For our experiments, we cultured C. reinhardtii in different types of media. The first experiment used TAP media because of the high phosphate concentration and ammonium as the source of nitrogen content. The second experiment used a mixed media of TAP and Allen media C. Allen media has lower phosphate levels and uses nitrate for nitrogen content. The third experiment used Allan media. C. reinhardtii was cultured in 15 ml conical tubes, while this was a convenient way to house C. reinhardtii it also resulted in large pellets forming in the bottom of the tubes. To fix this problem C. reinhardtii was cultured in Erlenmeyer flasks, which prevented pellet formation and allowed for more light to reach the cells.

Figure 3. Results of our first experiment using TAP media compared to an untransformed C. reinhardtii control. The results indicate that pL2-Psr1 possibly causes an increased rate of phosphate uptake of C. reinhardtii.

Figure 4. Results of our second experiment using mixed TAP/Allen media compared to an untransformed C. reinhardtii control, and chlamy transformed with BBa_K5078009. In this experiment, there was no evidence that pL2-Psr1 causes an increased rate of phosphate uptake of C. reinhardtii.

Figure 5. Results of our third experiment using Allen media compared to an untransformed C. reinhardtii control, and chlamy transformed with BBa_K5078009. In this experiment, there was no evidence that pL2-Psr1 causes an increased rate of phosphate uptake of C. reinhardtii.

Figure 6. Graph of the maximum rates of phosphate uptake in all three of our phosphate experiments of C. reinhardtii transformed with pL2-Psr1, two untransformed wild type strains, and C. reinhardtii transformed with our final plasmid (BBa_K5078009) in the different media types. C. reinhardtii transformed with Psr1 only outperformed untransformed C. reinhardtii in TAP media, which had the highest phosphate concentrations of any of the media we used for the assays. We speculate that at lower levels of phosphate, untransformed C. reinhardtii may turn on expression of its own Psr1 gene, causing it to uptake as much phosphate as our transformed C. reinhardtii.

Sequence and Features