The Effect Of Imidazolium Nicotinic Acid On The Cyclic Electron Transport Chain Of Arabidopsis Photosynthesis

Photosynthesis is very important metabolic pathway for plant growth and crop yield.This report investigated the effect of the herbicide Imazethapyr on the photosynthesis using the Arabidopsis thaliana mutants of pns B3 mutant(a defect in the NDH pathway)and pgr5 mutant(a defect in the PGR5 pathway).The results suggest that 20 ?g/L IM markedly inhibited the growth of the three ecotypes of A.thaliana,and produced more anthocyanins and ROS,especially to the pgr5 mutant.Chlorophyll fluorescence results showed that PSII was severely damaged in pgr5 mutant.Additional,cyclic electron transfer is stimulated significantly in Wt and pnsB3 mutant but not in pgr5 mutant.Real-time PCR analysis indicated that IM treatment considerably decreased the transcript levels of most photosynthesis-related genes examined in the three treated groups,but several genes(pgrl1A,pgr1B)in PGR5 pathway were significant induced in pns B3 mutant,while no one gene in NDH pathway was induced in pgr5 mutant.Gene transcription showed that the pgr5 mutant cannot compensate for the deficit in the pgr5 pathway by stimulating the NDH pathway,while the pns B3 mutant can compensate for the deficit in the CET cycle by regulating the pgr5 pathway.iTRAQ analyses showed that porphyrin and chlorophyll metabolism related proteins were down-regulated in pgr5 mutant,but part-related protein were up-regulated in wild-type and pnsB3 mutant,which showed that light absorption system and chlorophyll were severely damaged in pgr5 mutant.All the detected light-harvesting complex related-protein were up-regulated in pgr5 mutant,but some were down-regulated in wild type and pnsB3 mutant,which showed that pgr5 absorbed excess light energy,such produced excessive ROS in vivo,and suffered a greater light damage.PSII repair-related protein D1(PsbA)and OEC stability-related protein(PsbO)were significantly down-regulated,but PSI stability-related protein(PsaH)did not increase in pgr5 mutant;while PsbA have no significant change,and PsaH was significantly up-regulated in wild-type and pnsB3 mutant.These results indicate that the photosynthesis subject to a greater damage in pgr5 mutant.Glycolysis-related enzymes were significantly increased in pgr5 mutant,which may for the purpose of relieve the serious shortage of ATP by stimulating the glycolytic pathway.We also found that the accumulation of most of the TCA-related enzymes increased in Wt and pns B3 mutant.It was demonstrated that IM could induce several kind of organic acids secretion by stimulating TCA cycle,which could up-regulate the expression of alternative oxidase and affect multiple biochemical pathways to cope with stressor,but not in pgr5 mutant.All these results demonstrated that PGR5 pathway is more critical for electron transfer around PSI than the NDH pathway to resist in herbicide stress.