碩士 / 國立臺灣海洋大學 / 海洋生物研究所 / 107 / Diatom cells possess a distinctive nitrate transporter (encoded by Nrt2) and a sodium/phosphate cotransporter (encoded by Npt2bl), to enable the uptake of nitrate and phosphate from the environment. Since the metabolic pathways of nitrogen and phosphorus are both related to photosynthesis, the mRNA levels of Nrt2 and Npt2bl are assumed to have a diel variation in natural environments. In this study, research cruises were conducted in the coastal region rear Matsu Islands in June and July, 2017, respectively. During each cruise, a 24-h sampling program was established with additional nutrient-manipulative experiments performed at 2 time points. In a locally dominant diatom, Skeletonema subsalsum, RT-qPCR was used to measure the mRNA levels of the following genes, Nrt2, Npt2bl, FcpB (encoding fucoxanthin-chlorophyll protein), and TBP (encoding TATA Box binding protein). Next, nonlinear regression was applied to fit a cosine function to measured expression levels. The patterns of FcpB and TBP expressions were used as comparison standards to determine if diel variation existed in the expression patterns of Nrt2 and Npt2bl. Experimental results indicated that gene expression of FcpB reached the maximum at noontime and decreased to the minimum at midnight in June. Regression analysis generated a cosine function with an amplitude of 1.32 (logarithmic scale), which was statistically significant at p < 0.05. In July, the amplitude of FcpB regression equation was not statistically significant, but the maximum and minimum values still appeared at noontime and midnight. The amplitudes of TBP expressions were statistically significant in June and July, but the amplitudes were too small to properly reveal a diel change. In comparison, the gene expressions of Nrt2 and Npt2bl fluctuated in a day, but the amplitudes of regression curves were not statistically significant. In nutrient-manipulative experiments, the gene expressions of Nrt2 were mainly affected by the availability nitrogenous nutrients. Similarly, the gene expressions of Npt2bl were mainly affected by phosphate levels. For both genes, range of gene expression due to nutrient-manipulation was much wider than the range of variation in a day. Comparing the results of nutrient-manipulative experiments to those of in situ samples, the in situ expressions of Nrt2 were similar to ammonium-added treatments in June and July, indicating that S. subsalsum did not actively produce nitrate transporter. By contrast, gene expressions of Npt2bl revealed that S. subsalsum actively produced phosphate transporter in June, but the effort was moderate in July.
| Identifer | oai:union.ndltd.org:TW/107NTOU5270008 |
| Date | January 2019 |
| Creators | Huang, Wei-Kai, 黃威凱 |
| Contributors | Chang, Jeng, 張正 |
| Source Sets | National Digital Library of Theses and Dissertations in Taiwan |
| Language | zh-TW |
| Detected Language | English |
| Type | 學位論文 ; thesis |
| Format | 38 |
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