Optimization Screening Of Photorespiratory Mutants And Studying Of Photorespiratory Mutant Pglp1-2 In Arabidopsis Thaliana

Photorespiration is a metabolic pathway that flows through a variety of organelles and which regulatory mechanisms is complex.Although photorespiration consumes part of fixed carbon and energy and reduces crop yields,some research found that photorespiration is essential for normal growth of plants,which plays an important role in biological processes,such as regulating photosynthetic and maintaining cellular redox homeostasis balance.Due to the complexity of photorespiration,little is known about its regulatory mechanism so far.In this study,Arabidopsis Columbia?Col-0?was used as the experimental materials,which has been treated by ethyl methanesulfonate to produce random mutation.The photorespiratory mutants were screened by two methods.One is chlorophyll fluorescence imaging that based on low maximum quantum efficiency of PSII?Fv/Fm?in photorespiratory mutants,which grow in normal ambient air?400 ppm CO₂?.Another is photorespiratory phenotypes,which means photorespiratory mutants show chlorotic and dwarf phenotypes in normal ambient air but can grow as normal as the wild type in high CO₂?3000 ppm CO₂?conditions.The mutant 156-16 was selected by these principles.Under normal atmospheric condition,the mutant 156-16 grows slowly and shows chlorotic,yellow leaves,even cannot be flowering and fruiting.However,the 156-16mutant and wild type had no obvious difference in high CO₂ concentration condition.Gene mapping and the whole genomic sequencing showed that the mutant gene was AT5G36700,which encodes phosphoglycolate phosphatas 1?PGLP1?.The proPGLP1::PGLP1 plasmid was constructed and transformed into 156-16.The transgenic plants recovered to normal growth in the ambient air environment when compared with the wild type.Thus,the mutant156-16 was named pglp1-2.The tissue expression analysis of proPGLP1::GUS transgenic plants showed that PGLP1 was expressed in leaves,stems,flowers and pods,but not in roots.The fluorescence analysis of the 35S::PGLP1-GFP transgenic plants showed that PGLP1 was localized in chloroplast,which was coincident with the result of fluorescence analysis in tobacco.In addition,the phenotype analysis of the pglp1-2 mutant and the T-DNA insertion mutant pglp1-1 showed that pglp1-2 was a weak allele when compared with pglp1-1,the later could not be recovered by high level of CO₂ and even did not survive in atmospheric air.Enzyme activity measurements showed that the PGLP activities of pglp1-2 and pglp1-1reduced to 50%if compared with the wild type both in ambient CO₂ condition and high concentration of CO₂ condition.Orthophosphate content measurements suggested that orthophosphate contents of pglp1-2 and pglp1-1 was nearly as same as that of wild type.In summary,a photorespiratory mutant 156-16 was screened by chlorophyll fluorescence imaging and by high-low concentration of CO₂ condition.The gene mapping analysis and complementary experiment suggested that the mutant gene is PGLP1.PGLP1was localized in the chloroplast.Compared to the T-DNA insertion mutant pglp1-1,the mutant pglp1-2 showed a little weak photorespiratory phenotypes,which make it be a useful material for the further study of PGLP1.