Organic Acids And PM H~+-ATPase Involved In The Response Of Soybean (Glycine Max) Under Low Phosphorus Stress

Lacking of the phosphate nutrition in the soil and low effect utilization of soybeans were two of the limiting factors that influence the production of soybeans, so screening or breeding phosphate efficient varieties was the valid path to increase the utilization of phosphate. Phosphorus efficiency plant could promote plant activation and absorption insoluble phosphate under low phosphorus stress, by increasing the secretion of organic compounds, especially some organic acids. It played an important role in improving the phosphorus nutrition of plants. The nf37 and Jihuang13 were applied as materials to detect the effect of different soybean genotypes on secretion of H+ and organic acids under low phosphorus stress. The result showed that: both of soybean genotype cultivars could secrete H+ to external environment under low P concentration. Under the different phosphorus levels, the major forms of organic acids exuded from the roots included citric acid, oxalic acid, tartaric acid and malic acid according to the result of HPLC. Furthermore, all the organic acids above could utilize the citric acid soluble phosphorus obviously when this insoluble phosphate fertilizer was added into nutrient solution. The further test revealed that, phosphorus high efficient soybean genotype nf37 was more efficiently than phosphorus sensitive soybean genotype Jihuang13 on the utilization rate of citric acid soluble phosphorus and secretion of H+ and organic acids.Because of high cytosolic pH (7–7.5), citric acid dissociated into citrate and H+ in cytosol. This implied that the release of citric acid by proteoid roots must be attributed to at least two structurally separated plasma membrane transport processes: citrate export and proton export. Plasma membrane H+-ATPase had an important role in transport processes of H+, and it was a crucial factor in the survival of plants when they were under a variety of environmental stresses. In this experiment, a semi RT-PCR system was establishment to detect the gene expression of PM H+-ATPase in soybean root under phosphorus deficiency quickly and conveniently, in whichβ-tubulin gene was used as reference gene. The results showed that the gene of PM H+-ATPase was up-regulated under low P environment for 24 h and increased gradually until 4 h, but the gene expression decreased a little with the time delayed to 6h. It was suggested that gene expression changes of PM H+-ATPase may related to the adaptation of the phosphorus deficiency stress.The results proved manifestly that the organic acids and PM H+-ATPase involved in the response of soybean to phosphorus deficiency, and showed significant difference between phosphorus efficiency and phosphorus sensitive genotypes.