Screening And Characterization Of Low-nitrogen Tolerant Mutants Of Arabidopsis Thaliana

Application of chemical fertilizer has promoted a great development in agricultural production. However, injudicious use of chemical fertilizer, especially chemical nitrogen fertilizer has induced a crucial negative impact to sustainable agriculture development, such as decrease of fertilizer utilization efficiency, reduction of agricultural product quality, and environmental pollution. But modern breeding is always proceeding under standard condition, so the high absorbing and using ability of plants under low nutrient stress are not exerted.Activation tagging is a new method for isolation and functional identification. It can generate dominant gain-of-function mutants by over expression of a particular endogenous gene. The mutant-isolation experiment is based on large seed pools (T2) which are mutagenized by activation tagging.A hydroponic system was designed for Arabidopsis, which is based on two units: a seed-holder and a tank. The quartz sand-containing seed-holder allows not only direct culture of seeds, but transplant of seedlings. Effects of low nitrogen stress on germination and growth of Arabidopsis thaliana were studied and the corresponding N concentrations for screening mutants were determined as 0.18mmol/L. Under this concentration, growth of wild type was restrained but mutants will be alive.By using floating system and corresponding screen pressure, T2 populations (seed pool) were screened for low nitrogen tolerant mutants with high efficiency and low maintenance. During the culture, with chlorophyll SPAD scores and other biological characters, 6 plants (T3) were selected for putative mutants at first round, 7 plants (T4) were selected at second round, and 8 plants (T5) were selected at third round.After the isolation, 4 plants (T5) were selected to have herbicide test and 5 plants (T6) resisted herbicide and were still alive. Then chlorophyll content, total N, P, K content of those 5 putative mutants (T6) under low-N stress were measured and they are similar with those of wild type under standard condition. These results show that 5 plants have good absorbing capacity of nutrients under low nitrogen stress.Due to the whole results, 5 low-nitrogen tolerant putative mutants of Arabidopsis thaliana were isolated and their physiological and biochemical characters of nitrogen nutrient were studied. It could provide the materials to identify and separate its corresponding gene.