Cloning And Preliminary Functional Analysis Of Potassium Transport-Related Genes In Soybean

Soybean[Glycine max(L.)Merr.]has been regarded as one of the important economic and food crops.However,the yield and nutritional qualities of soybean would be reduced by some biotic and abiotic factors,such as salt stress,drought,insect pests,and low-potassium stress.Especially potassium deficiency in soil has become a serious problem in recent years,though potassium is one of the three necessary nutritional elements for plants.Therefore,it is very significant for screening the improved germplasm resources of low-potassium-tolerant soybean varieties,and for the mechanism related researching on molecular genes level.In order to study the mechanism of low-potassium tolerance at the molecular level of soybean Lee68,which was screened from 25 soybean varieties by biomass under low potassium stress,and was used as test materials in transcriptome sequencing.Through the analysis of Solexa/Illumina sequencing data,160,211,759 reads were obtained.By gene sequence alignment with soybean Wilams82 genome,the compare rate reached more than 92.83%.The total differential expressed genes of LK_VS_CK were 3521,of which down/up-regulated genes were 2393/1128 respectively.The GO terms analysis showed that the differential expressed genes in the LK_VS_CK group were mainly enriched in plant metabolic processes,stress response,and signal transduction.The KEGG pathway analysis showed that there were 390 differential expressed genes in LK_VS_CK group and enriched in 19 pathway approach,especially in the metabolic pathways,including amino acids,fatty acid and lipid metabolism,and carbohydrate metabolism.COG classification statistics showed that in the LK_VS_CK comparison group,beside the 649 differentially expressed genes with general function,377 genes were classified into the function of transcription,and 343 genes were classified into the function of signal transduction mechanism.Combination the function analysis of differential expressed genes with jasmonic acid signal transduction regulation mechanism,seven key candidate genes were screened as follow:GmJAZ1,GmMYC2,GmCHX20,GmCHX15,GmKUP1,GmKEA5 and GmHAK5,which may participate in the uptake of potassium ion transport process in Jasmonic acid signaling pathway.These results provide an important reference for further study on the regulation and cloning of genes related to potassium efficient absorption in soybean under potassium stress.Bio-informatics analysis indicated that that GmJAZ1 contains the typical domain of TIFY and Jas.GmMYC2 contains the typical bHLH domain in N-terminus,and belongs to the typical transcription factor of MYC2 family genes.Both of GmKUPl and GmHAK5 have typical potassium ion transport domains and functions,which belong to potassium transporters.GmKEA5,GmCHX20,and GmCHX15 belong to the subfamily NHX(Na+/H+Exchanger)of the CPA potassium transporter family,and play important roles on Na+/H+exchanging and Na+/K+homeostasis maintaining in plants.RT-PCR results showed that the transcription levels of the above seven genes were significantly up-regulated under low-potassium stress compared with the control,which consistent with the result of transcriptome.In addition,it was found that the expression patterns of these 7 genes in Jackson(sensitive to low-potassium)are opposite to those of Lee68(tolerant to low-potassium).Seven genes in both these two varieties can be induced by the jasmonic acid,which may be involved in the process of absorption and transport of potassium ion in soybean mediated by jasmonic acid signal.