부산대학교 도서관

Nitrate reductase (NR) is a key enzyme for nitrogen assimilation in plants, and its activity is regulated by posttranslational phosphorylation. To investigate the effects of dephosphorylation of the NIA1 protein on the growth and the physiological and biochemical characteristics of rice under different forms of nitrogen supplies, the phenotypes, nitrogen metabolism and reactive oxygen metabolism were measured in NIA1 phosphorylation site-directed mutant lines (S532Dand S532A), an OsNia1over-expression line (OE) and Kitaake (wild type, WT). Compared with WT and OE, S532Dand S532Ahave stronger nitrogen assimilation capacities. When ammonium nitrate served as the nitrogen source, the plant heights, dry weights of shoots and chlorophyll (Chl) contents of S532Dand S532Awere lower than those of the WT and OE, whereas hydrogen peroxide (H2O2), malondialdehyde (MDA) and nitrite contents were higher. When potassium nitrate served as the nitrogen source, the plant heights, dry weights of shoots and Chl contents of S532Dand S532Awere higher than those of the WT and OE, there were no significant differences in the contents of H2O2and MDA in the leaves of the test materials, and the difference in nitrite contents among different lines decreased. When ammonium sulfate served as the nitrogen source, there were no significant differences in the physiological indexes of the test materials, except NR activity. Compared with ammonium nitrate and ammonium sulfate, the content of NH4+-N in the leaves of each plant was lower when potassium nitrate was used as the nitrogen source. The qPCR results showed that OsGSand OsNGS1were negatively regulated by downstream metabolites, and OsNrt2.2was induced by nitrate. In summary, when ammonium nitrate served as the nitrogen source, the weak growth of NIA1 phosphorylation site-directed mutant lines was due to the toxicity caused by the excessive accumulation of nitrite. When potassium nitrate served as the nitrogen source, the assimilation rates of nitrate, nitrite and ammonium salt were accelerated in NIA1 phosphorylation site-directed mutant lines, which could provide more nitrogen nutrition and improve the tolerance of rice to ammonium nitrogen deficiency. These results could provide a possible method to improve the efficiency of nitrogen utilization in rice under low-nitrogen conditions.