The Functional Analysis Of Atmgt4, A Member Of Putative Mg²⁺ Transporter Family In Arabidopsis

Magnesium(Mg²⁺)is the most abundant divalent cation in plant cells and plays a critical role in many physiological processes in plant cells. Legong Li identitied a 10-member arabidopsis gene family-AtMGT encoding putative Mg²⁺transport proteins.Four members of the AtMGTs had been proved to have Mg²⁺transport activity.While all the researchs about the family were focused on the transport function of those genes, there's little report about the gene's function during the plant growth and development process.According to sequence homology analysis,10 members of the AtMGTs could be subdivided into 5 clusters,in which AMGT4 and AtMGT10 locus on a single cluster respectively,and share little homologous sequence with other members.This research was based on the AtMGT4 gene,planning to study AtMGT4 gene's function during the plant growth and development process by mutating and overexpressing this gene.Since during the research processes,neither of the T-DNA insertion mutants and the RNA interference transgenetic plants with heritable particular phenotypes could be obtained,overexpression of this gene was the mainly object used to study the function of the AtMGT4 gene. Overexpression vector pBI121-AtMGT4 was constructed by fusing the CDS of AtMGT4 and pBI121 vector that contains 35S promoter,and pBI121-AtMGT4 transgenetic plants were obtained by floral dip.During the courses of screening overexpression plants and phenotype observation, we found that the vegetative and reproductive growth of the overexpression plants were influenced by overexpressing of AtMGT4. Compared with the wild-type plants,some of the overexpression plants showed particular phenotypes,such as curled leaves,clustered flowers,dwarfing,late flowering and abnomal leaf trichomes,etc.TAIL-PCR result showed that the particular phenotypes of overexpression plants were not caused by gene mutation result from the T-DNA insertion. Semi-quantitative analysis revealed that RNA levels of AtMGT4 were closely related with the particular phenotypes in overexpression plants, and overexpression plants with particular phenotypes had higher RNA levels of AtMGT4 comparing with wild-type plants.The determination of Mg²⁺content showed that the Mg²⁺content in the overexpression plants was half the level of the wild-type plants,and the Mg²⁺content in the rosette leaves and the main stems of the same plant had little difference. The drought resistance and the salt tolerance of the overexpression plants was less than the wild-type plants,and the dehydration of the overexpression plants was faster than the wild-type plants.Meanwhile, fusion protein of AtMGT4 gene was highly expressed and the polyclonal antibody of it was prepared by immunization,and then the specificity of the antibody was detected on prokaryotic level.