Transformation Of Arabidopsis Thaliana Magnesium Transporter Gene, AtMGT1, In Medicago Sativa L

Alfalfa(Medicago sativa L),known as "king of forage",is a highly valued forage legume that is cultivated on more than 35 million hectares in the warm temperate and cool subtropical regions all over the world.Alfalfa produces a greater yield of protein and essential amino acid per hectare than any other crop.Furthermore,the alfalfa, which intergrows with the rhizobium,could even improve the soil fertility when their roots could grow normally.Aluminum(Al)is one of the most abundant elements present in the crust.When the soils pH value is lower than 5.5,Al exits as Al³⁺,which is abroad toxic to cells.By the assessment of researchers,Al toxicity is the major limiting factor for plant productivity.Based on an estimate of the world's potentially arable land resources, most of the cultivable area(78.4%)is composed of acid soils and that proportion is increasing.So it is very important to improve alfalfa aluminum tolerance in order that they could grow better in acid soils.Some aluminum-tolerant plant breeds have been achieved by the great improvements of gene engineering techniques.Recently,an Arabidopsis magnesium transporter gene,AtMGT1,have been reported as an aluminum-tolerance conferred gene.The overexpression of AtMGT1 could improve the uptake and the accumulation of Magnesium,which is the essential element of the plant growth,in the cells.It also could improve the cells aluminum tolerance when it been overexpressed.Base on previously research,we transformed an AtMGT1-overexpresstion construct into a Medicago sativa L breed,which calls "BaoDing",try to achieve a new breed with better aluminum tolerance.The main results are as follows:1.We got a plenty of T₀ generation alfalfa plants,which belong to several lines. The result of histochemical visualization of GUS shows the constructs carrying AtMGT1 gene have been introduced into plants' genome.2.We applied Mg-deficient treatments by using the transgenic seedlings and the wild-types as materials.The results show the difference of the phenotypes:the transgenic grows normally at all treatment.But the wild-types shows a descending Mg-deficient phenotypes when Mg²⁺content is digressing.This result is according with previously report,and it also proves the AtMGT1 has been introduced by plasmid construct.3.We applied a root elongation inhibition experiment by using the shoots of transgenic plants and wild-types.The result,which is described by difference values, shows that the transgenic shoots have a better roots elongation at 100μM AlCl₃. However,the wild-types' roots hardly grew with poor elongation.This result shows the overexpression of AtMGT1 could improve the aluminum tolerance of alfalfa.This result also proves our previously hypothesis.The introduction of the gene has been further proved.