Screening Lanthanum-Resistance Mutants Of Arabidopsis

Rare earth elements(REEs) has been applied widely in agriculture ,especially application of REEs chemical fertilizer quicken the enrichment and accumulation of rare earth in the soil and environment.Because RE are heavy metal,the effects of REEs on the entironment and human body have aroused whole society attention. At the present time, study of REEs'effect on the entironment after accumulated in the soil has obtained a few fruit, but study of REEs'effect mechanism on the plant has no system.Arabidopsis is a mode plant. Its heredity resource has been exploited and utilized in the different field of biology. Arabidopsis's many mutants have been used for the study of plant growth and metabolize pass. Screening mutants of Arabidopsis have been precondition of many important theory question solved. But utilization of Arabidopsis in REE used in agriculture is few, the study of screening REE-resistance mutants of Arabidopsis is absence at presence.This study tries to screen La-resistance mutants of Arabidopsis. The mutants will provide base material for gene mapping of La-resistance. The study of La-resistance mutants of Arabidopsis will clarify heredity effect of REE accumulate from the angle of gene , fill up the blank of REE study,perfect environment security evaluate system of REEs'application in agriculture.Due to La³⁺ occuring deposition with other negative ion, it reduces the efficiency concentration of La in the medium, also cause La distributing asymmetry at the same time, and go against mutants'screening, so the condition of screening is explored. At the condition of pH5.8,0.8% agar, white deposition appears in the medium containing 1/2MS+20 mg/kg La ,plant are also able to grow at the 50 mg/kg La³⁺.In order to avoid ionic deposition, base medium containing 1/2MS(-P)and medium containing pure La are tested. 20 mg/kg La³⁺ restrains entirely growth of seeding taproot, furthermore both examinations'result are same,so the medium containing pure La is established for screening medium. In order to the uniformity of La in the medium, and avoid CO2 of air getting deposition, pH is brought to 5.5.Through two-layer solid-medium of screening method experiment,roots could grow through the upper layer and penetrate the lower layer containing 50mg/kg La³⁺.Stem and leaf are under the non-intimidate ,and La absorbed by roots of the plant is transfer few to the upside,so seeding can endure even more higher concentration. In view of inoculating quantity in per vessel being finity, and seed germination being variance, and growth condition of root being very hard to control, the screening method using the root-bending assay is selected.Among the screening stress experiment,root-bending is consistent to CK in the medium containing 6 and 6.5mg/kg La³⁺;in the medium containing 7 and 7.5 mg/kg La³⁺ the plant can grow ,but it grow slower than CK,and the root-bending length is shorter. It cannot grow in the medium concaining 8mg/kg and up La³⁺.The medium containing La³⁺ is softer than CK,and that concentration of La³⁺ higher ,medium softer .Because agar dosage and pH of medium have complementary effect in improving solidification , fine solidification is gained when agar concentration increasing to 1.0% at pH5.5. Arabidopsis is restrained at La³⁺ from 7mg/kg to 13mg/kg, but still can grow, and it cannot at and up 14 mg/kg La³⁺. 14mg/kg La³⁺ concertration of Col-0 Arabidopsis be entirely incapable of growing is selected for the best screening pressure at pH5.5 and 1.0% agar.Using the above selected screening concentration and screening method the 5120 T2 series (about 50,000 seeds) are screened. 63 putative mutants are obtained, and cultured in nutritional soil, harvested disparting individual plant. In the process of culture a later ripe plant of later 15 days than CK is discovered.63 putative mutants are identified using the previous method, La-resistance mutant of stable heredity is not yet discovered.