Study On Function And Molecular Mechanism Of GmNPR1 In Soybean Nodulation

Soybean(Glycine max L.)is one of the most important grain and oil crops in the world.It has important economic value and high consumption demand.At present,our self-sufficiency in soybeans is still at a low level.In order to ensure the national food security,it is necessary to increase the yield of soybean per unit area under the condition of limited arable land.The roots of legume plants can form nodules in symbiosis with the rhizobium bacteria in the soil.The nodules transform nitrogen from the atmosphere into biological nitrogen sources through nitrogen-fixing enzymes,which provide nutrients for the growth and development of crops.Biological nitrogen fixation is an important factor affecting the high yield of soybean.Therefore,improving the nitrogen fixation efficiency of soybean root nodules is the key to high yield of soybean.salicylic acid(SA)is a major player in the process of acquiring resistant SAR in plant trigger systems.A large number of studies have demonstrated that NPR1 is a key regulatory gene in SAR and plays an important role in regulating the expression of downstream PRs protein.Although biological functions related to NPR1 have been reported in Arabidopsis thaliana,the regulatory role of its homologous gene GmNPR1 in soybean nodulation remains unclear.Through a series of experiments,this study reached the following conclusions:(1)In this paper,the homologous gene of Arabidopsis At NPR1 in soybean was first identified by bioinformatics analysis,and then the gene was cloned by molecular biology and named GmNPR1.The protein domain of GmNPR1 has changed,indicating that its function may have diverged.(2)The constitutive expression of GmNPR1 was analyzed.GmNPR1 was expressed in all tissues,and tissue localization in roots showed that GmNPR1 was expressed in the main root crown and mature area.Subcellular localization showed that GmNPR1 was localized in the nucleus.(3)GmNPR1 expression was upregulated after inducing by rhizobium.Overexpression of GmNPR1 inhibited hairy root nodulation in transgenic complex plants,while functional loss of GmNPR1 promoted nodulation,indicating that GmNPR1 negatively regulated nodulation in soybean.(4)Exogenous application of 40 μM SA inhibited root elongation and increased GmNPR1 expression of soybean seedlings,and the presence of SA inhibited root nodules formation.(5)Both SA and its receptor GmNPR1 are negative regulators of the nodulation pathway.When SA and overexpressed GmNPR1 exist simultaneously,this negative regulatory effect can be superimposed to further reduce soybean nodulation,suggesting that SA and GmNPR1 may play a role in the same signaling pathway.(6)Through bioinformatics analysis,four haplotypes of GmNPR1,Hap1,Hap3 and Hap4 were identified,and the influence of different haplotypes on tumor formation was preliminatively explored.Excellent haplotypes of GmNPR1 were selected,which will provide gene resources and theoretical guidance for efficient nitrogen fixation tumor formation in soybean.In this study,the homologous gene GmNPR1 of At NPR1 in soybean was found by homologous comparison,and the biological function of GmNPR1 in regulating soybean nodulation was analyzed by means of molecular biology and bioinformatics.By analyzing the molecular mechanism of GmNPR1 affecting soybean nodulation genetics,it laid the foundation for the ultimate realization of efficient molecular design breeding of soybean nitrogen fixing molecules.