Influences Of OsPT6 Gene Overexpression On Nodulation And Nitrogen Fixation Of Vegetable Soybean Under Low Phosphorus Conditions

Vegetable soybean[Glycine max(L.)Merr.],also known as ’mao dou’,has become highly popular with consumers in China and Southeast Asia and gradually in Europe and America because of that it’s rich in protein,amino acid,vitamins,minerals,fiber.Phosphorus deficiency is one of the major factors that limit legume nodulation and nitrogen fixation,and thus legume productivity,especially in the red soil in south China,in which phosphorus can easily be fixed,so that the natural soil phosphorus content is very low.The rice OsPT6 gene encodes the protein that is high-affinity phosphate transporter,which plays a major part in the process of phosphate uptake and translocation throughout the plant.OsPT6 gene overexpression enhances the ability of vegetable soybean to tolerance of low phosphrus conditions.Using sand culture,comparisons were made between the T3 transgenic lines overexpressed a rice(Oryza sativa L.)phosphate transporter gene OsPT6 and their non-transgenic(NT)host cultivar to examine the differences in the traits of growth and development,the contents of available phosphorus,total phosphorus,total nitrogen,and leghemoglobin,the activities of glutamine synthetase and the contents of seed proteins in vegetable soybean under low phosphorus conditions.In addition,the relative expression levels of some genes related to the nodulation and nitrogen fixation in nodules were also measured.The purpose of this research was to investigate whether OsPT6 gene overexpression promote the ability of nodulation and nitrogen fixation in the roots of the transgenic plants under phosphorus deficiency.The main results are as follows:1.By using PCR to measure the expression of GUS gene and OsPT6 gene and using qRT-PCR to measure the relative expression levels of OsPT6 gene,to reconfirm the materials are transgenic plants.The indicators of growth and development including the plant height,stem diameter,numbers of flowers,and pods of the transgenic plants were significantly higher than those of the NT plants.The results revealed the vegetable soybean with OsPT6 gene overexpressing can grow well under low phosphorus conditions.2.The efficiency of photosynthesis and the concentrations of available phosphorus in roots,stems,leaves and nodules,the contents of phosphorus in total plant,were significantly higher than those of the NT plants.3.The contents of nitrogen and the nodule numbers in the whole plant,the concentrations of leghemoglobin and the activities of glutamine synthetase were significantly higher than those of the NT plants.The mutually correlations among the concentrations of leghemoglobin,total nitrogen,and the activity of glutamine synthetase were outstanding positive which were observed.The relative expression levels of GmENOD40a,GmENOD40b,GmGS1β1,GmGS1β2 genes that are related to the nodulation and nitrogen fixation in roots measured by using qRT-PCR in transgenic plants were significantly higher than those in the NT plants.