Influnences Of Different Levels Of Nitrogen On Caborn And Nitrogen Metabolisms In Transgenic Rice Plants Expressing Maize PEPC Gene

C4plants has higher photosynthesis, water use efficiency, physiological N utilization efficiencyand crop yield compared with C3plants. The reason is the key enzyme of phosphoenol pyruvatecarboxylase of C4plants has higher affinity with CO2. So, the scientists tried to introduce thephotosynthetic characteristic of C4plants into C3crop to improve the photosynthetic efficiency,physiological N utilization efficiency and crop yield. Previous studies showed that the PEPC of C4participate in anaplerotic reaction of Krebs cycle(TCA) in C3plants, and influence the nitrogenassimilation，amino acid metabolism and organic acids content of C3plants. However, there is still acontroversy in whether the PEPC in transgenic plants increased the crop yield. In the presentresearch, the PEPC transgenic rice was investigated to analyze the effects of carbon assimilation,crop yield and nitrogen assimilation under different nitrogen application levels. The main results areas follows:(1). The transgenic rice plants compared with untransformed rice plants shower higher yieldunder low nitrogen level. The transgenic rice plants compared with untransformed rice plants was nosignificant difference in the number of panicles per plant and grain number, the yield per plant wasincreased of the transgenic rice plants under low nitrogen and normal nitrogen levels. The resultsindicated that the yield of ZM21plants increased by7%and13%, the thousand grain weight wereincreased by3%and2%, and yield of ZM30were increased by2.2%and2.6%under N1and N2levels. And the thousand grain weight of ZM30was increased by3%under N2level. The yield oftransgenic rice were reduced by16.5%and6.9%under high nitrogen level. The reason is the thenumber of productive ear were reduced by12.3%and10.6%. So, the present results showed that, thePEPC gene overexpressed rice is helpful to increase the1000-grain weight, then contribute toenhance the yield.(2). The transgenic rice plants compared with untransformed rice plants shower higher carbonassimilation under low nitrogen level. The content of soluble sugar of transgenic rice leaves weresignificantly increased compared with the untransformed rice leaves in jointing stage and floweringstage under low nitrogen level. With the growth period, the soluble sugar into starch andaccumulated in the seeds, and so, the content of soluble sugar of transgenic rice seeds weresignificantly reduced compared with the untransformed rice. The content of starch of transgenic riceseeds were significantly increased compared with the untransformed rice under low nitrogen level.So, the transgenic rice plants have higher carbon assimilation capacity than the untransformed riceunder low nitrogen level. The reason is the activity of ME was significantly increased under lownitrogen level. The ME catalyze malate decarboxylation and release more CO2into Calvin cycle. So,the transgenic rice plants with a higher carbon assimilation capacity under low nitrogen level.(3). The transgenic rice plants compared with untransformed rice plants shower higher nitrogenassimilation under low nitrogen level. The activity of NR, GS and GOT of the transgenic rice plantswere higher than the untransformed rice plants under low nitrogen level. And the content of amino acid, soluble protein and N of the transgenic rice plants were significantly increased, and the C/Nwas significantly reduced under low nitrogen level.(4). The amino acid synthesis was changed in the transgenic rice plants. Compared withuntransformed rice plants the activity of MDH significantly increased in transgenic rice plants. Thecontent of pyruvic acid, malata were significantly increased in transgenic rice plants, and the contentof PEP was significantly reduced, the content of skeleton carbon of amino acid synthesi was changed,And various of amino acid components was changed. Therefore, the overexpressed of PEPC genechanged amino acids metabolism and the content of organic acids.