The Physicological Response Of Oxalic Acid Stress On Arabidopsis Thaliana And The Premilinary Screening Of Oxalic Acid Insensitive Mutants

Many phytopathogens can seccrete oxalic acid(OA)which is the crucial pathogenic determinant and plays an important role in infection process.OA has a close correlation with the pathogenicity,virulence of pathogen.In this project,model plant Arabidopsis thalinana was used to study plant physiologic response to the OA stress with different concentrations and time course.The major results were as follows:1.OA stress induced the change of reactive oxygen metabolism in Arabidopsis. Under OA stress.SOD and PAL activities were enhanced,GSH content increased,but POD and CAT decreased.Finally it leads to the accumulationof ROS,and aggravation of lipid peroxidation,then MDA accumulated.2.The amount of 20～25mmol·L^-1OA might be a threshold to maintain the balance of producing and eliminating reactive oxygen free radicals under OA stress. Above the threshold,SOD and PAL activities were reduced instead of being enhanced, and CAT activity decreased rapidly.3.Under the 30mmol·L^-1OA stress,SOD activity was first enhanced to reduce cumulation of O₂^-·.But immediately,POD,CAT and GSH were all extremely reduced so that it resulted in the accumulation of H₂O₂,and increase of MDA in 24h.GSH activity enhanced in 24h,but H₂O₂ wasn't eliminated in time.So the inhibition of the activities of POD and CAT might be the reason cause Arabidopsis' s cells impairment by OA.4.Mutant screening is the important method to study the related gone function. In this project,we obtained the the proper screening concentration of oxalic acid was 2.0 mmol·L^-1.Fourteen A.thaliana mutants with enhanced resistance to oxalic acid were obtained after screening twice in medium from activitation tagging mutant library construced by our library(about 5000 individual lines),and then confirmed with an increase to an extent of 30mmol·L^-1.This concentration of OA causes severe damage to Arabidopsis.The fourteen mutants were more resistant to this high concentrations of OA compared with the wild type.These results will facilitate the further study to understand the physiological, biochemical and genetic mechanisms for plant response to the OA stress.