Study On Nitrogen Uptake Characteristics In Arabidopsis Thaliana Nitrate Transporter Mutants

AtNRT1.1, AtNRT1.2, AtNRT2.1 and AtNRT2.2 are the members of NRT genes which play important roles in nitrate uptake in Arabidopsis thaliana. AtNRT2.1 and AtNRT2.2 need interact with AtNAR2.1 to transport nitrate. However, what are the differences between the nitrate transporter gene mutant and the wild type in nitrate uptake capacity and nitrogen efficiency? In order to figure it out, Arabidopsis wild type col and Arabidopsis thaliana nitrate transporter gene mutants(atnrt1.1, atnrt1.2, atnar2.1, atnrt2.1 and atnrt2.2) were selected as tested plants to study their nitrogen uptake dynamics and absorption efficiency via whole growth stage solution cultivation experiments. The thesis aims to identify the nitrate uptake characteristics of the nitrate transporter gene mutant of Arabidopsis thaliana and thus provide materials for the study of the function of the nitrate transporter genes in other crops. The main conclusions of the thesis are as follows:(1) The curves of nitrate uptake dynamics of the mutant atnar2.1, atnrt1.2 fitted the Michaelis-Menten enzyme kinetics model, and the NO3- uptake rates increased along with the increasing of NO3- concentration in the solution in a certain range of substrate concentration. And the NO3--N uptake kinetic parameters(Vmax and Km)of different Arabidopsis mutants are quite different. The mutants atnrt1.2 and atnar2.1 had lower NO3- uptake rates compared to the wild-type. The curves of nitrate uptake dynamics of the mutant atnrt1.1 was similar to the curves of nitrate uptake dynamics of the mutant atnar2.1 and atnrt1.2. The curves of nitrate uptake dynamics of the mutant atnrt2.1 and atnrt2.2 did not fit the Michaelis-Menten enzyme kinetics model.(2) Shoot dry weight and shoot N accumulation in the mutants atnrt1.2 and atnrt2.2 Arabidopsis were significantly lower than that in the wild-type of Arabidopsis under low nitrate conditions(0.5 mmol?L-1). The shoot N content and N accumulation in the mutants atnrt1.1 and atnar2.1 were significantly lower than that of in the wild-type of Arabidopsis under high nitrate conditions(5 mmol?L-1).