| Summary: | 碩士 === 國立臺灣大學 === 分子與細胞生物學研究所 === 97 === For most of plants, nitrate and ammonium are the two major nitrogen sources. Nitrate taken into plants can be stored, or assimilated first to ammonium and then incorporated into carbon skeleton to generate amino acids. Excess ammonium is toxic to most plant. To avoid the toxicity, ammonium has to be incorporated into amino acids in chloroplast efficiently. In addition, nitrate and ammonium transport and assimilation system should be precisely regulated to keep balanced with energy, reducing power and carbon fixed from photosynthesis. About 10 % of the photosynthesis outcome is used in nitrogen metabolism. Nitrogen metabolism and carbon fixation are the most energy consuming pathway for plant. To avoid competition, these two pathways have to be coordinately regulated. However, the interaction and regulation mechanism between nitrogen metabolism and carbon fixation remain to be elucidated.
In this study, using genetic mapping and microarray analysis, an Arabidopsis ammonium sensitive and chlorate resistant mutant was found to be mutated at At4g14605 gene. Although At4g14605 is predicted to be a mitochondrial transcription termination factor-related protein, we found that it is targeted to chloroplast, and affect the expression of several photosystem II (PSII) related gene. Therefore, blocking the function of this gene will disrupt the normal assembling of PSII complex and reduce the cyclic electron transfer chain in photosynthesis, a key process to provide reducing power for carbon fixation and nitrogen metabolism.
|
|---|
