Study On The Relationship Between Protein Phosphorylation And Aluminum-tolerance In Soybean

In this work,the relationship between protein phosphorylation and aluminun(Al)tolerance in soybean is studied.The cDNA library was constructed from the root tips of Al resistant genotype soybean(BX10)and Al sensitive genotype soybean(BD2)after exposing to Al stress for 48h,and then were subjected to high throughput sequencing.A total of 11 differentially expressed protein kinase and protein phosphatase genes were screened,among which 7 protein kinase genes was up regulated by aluminum stress.However,the expression of one protein phosphatase gene in BX10 decreased significantly,but there was no significant change in BD2.Through the comparative analysis to the sequencing data,we speculated that Al tolerant soybean under aluminum stress may have higher phosphorylation level and participated in the signalling transduction and response to Al stress.Further,we measured the activity of protein kinase at 0,12,24,48,72 and 96h Al treatments.It was found that the activity of protein kinase in the root of two genotypes of soybean was not much changed at the early stage of Al treatment,but the activity of protein kinase began to rise after 12h treatment.The activity of gene type soybean protein kinases was significantly higher than that of the corresponding control group after 24h treatment.The protein kinase activity of BX10 soybean roots was significantly higher than that of BD2 after Al treatment,which showed that Al induced the expression of protein kinase in root cells,and the expression level was related to the exposing time of Al stress and genotype.SDS-PAGE results showed that the serine/threonine phosphorylation level of two genotypes soybean(37Kda)increased after Al treatment,of which the phosphorylation level increased by 107.1%in BX10 and by 69.4%in BD2 after Al treatment,indicating that Al stress promoted the protein phosphorylation.Considerring that melatonin(MT)could improve the activity of protein kinase,we used sensitive soybean BD2 as the material.We found that spraying exogenous MT could significantly increase the protein kinase activity and protein phosphorylation level of soybean leaves and roots in BD2.Al stress decreased the activity of SOD,CAT and POD in the leaves of soybean seedlings,increased the accumulation of MDA and the permeability of the membrane.What's more,Al stress decreased the photosynthetic rate and transpiration rate of the seedlings,and also the dry and fresh weight of the seedlings,and resulted in growth inhibition of the soybean seedlings.However,MT could effectively improve the antioxidant enzyme activity of soybean seedlings under Al stress and reduce its membrane lipid peroxidation,by which alleviated the damage of Al stress to the chloroplast PS?,enhanced the photosynthetic performance,and increased the dry and fresh weight of the seedlings,thus promoting the growth of the seedlings and effectively alleviating the damage caused by A1 stress.In conclusion,Al stress induced increased protein kinase activity and increased protein phosphorylation level,indicating that protein kinase is involved in signal transduction process of Al stress.MT can improve protein kinase activity,promote protein phosphorylation and alleviate Al stress in soybean.The results can provide theoretical guidance for improving soybean cultivation in acidic soils.