Functional Study Of Trehalose Metabolism Pathway In Soybean (Glycine Max) Nodule

Soybean(Glycine max)nodule,the symbiont of soybean and Rhizobium,is significantly contributing to global nitrogen cycling and reducing nitrogen fertilizer employment.Previous studies suggest T6P(Trehalose-6-phosphate)-central trehalose metabolite pathway can reflect and regulate sucrose level in the Arabidopsis thaliana.Trehalose specifically accumulating in soybean nodule implies that trehalose metabolism may have an important function in soybean development and nodulation.This study mainly focuses on the preliminary function of this pathway in soybean nodule.The main results are as follow:18 TPS(trehalose-6-phosphate synthase)genes,17 TPP(trehalosephosphatase)genes and a solo TRE(trehalase)gene were found and named in this study.The expression level of detected GmTPSs,GmTPPs and the GmTRE1 were increased with nodule development,and they were induced by low phosphate stress.According to the Attps1 supplementary experiment,three GmTPSs that closely relate to AtTPS1 showed TPS catalytic activity.It suggests that soybean trehalose metabolite pathway is active in gene expression and protein function,and it may participate in soybean development.Because of the sole GmTRE1 gene was specifically expressed in soybean nodule,the study of GmTRE1 protein’s localization and function in soybean nodule was mainly focused in this research.Histochemical localization analysis in transgenetic root hair and nodule suggested Gm TRE1 was mainly expressed in nodule infection zone.Subcellular localization analysis of tobacco suggested that GmTRE1 protein had signal peptide sequence and localized on the plasma membrane plant cell.These results indicate that GmTRE1 protein mainly functions in the infection zone of mature nodule,taking part in trehalose metabolism or other regulation pathways.To inhibit Trehalose metabolism in soybean by Validamycin treatment will induce more nodule number and bigger nodule size.It suggests increased trehalose concentration will promote nodule initiation and development.To further study the influence of GmTRE1 activity on nodulation,GmTRE1 overexpression and knock out transgenetic soybean were successfully obtained in this research.It showed that the nodule number and nodule biomass were reduced in GmTREl overexpression lines under the normal nutrient condition,suggesting enhanced trehalose metabolism will inhibit nodule formation and development.On the other hand,GmTRE1 knockout lines showed no obvious difference of soybean development and nodulation with wildtype,suggesting reduced GmTRE1 activity can be compensated by trehalase activity of Rhizobium.It indicates that trehalose metabolism pathway is manipulated by soybean and Rhizobium.Under low phosphorus stress condition,different trehalase activity had little effect on soybean development or nodulation.It suggests that activities of trehalose metabolism-related enzymes may had not been increased by low phosphorus induction,and their impacts on nodule initiation and development are probably indirect and not obvious.