Comparative Analyses Of Photosynthetic Complexes In Different Crops And Preliminary Investigation On The Function Of Genes With High Photosynthetic Efficiency

Photosynthesis is the major source of energy for nealy all life on Earth.In the severe period when global extreme weather events occur frequently and the harvest index is close to the limit and farmland could hardly be increased,high and stable crop yields are the key to sustain global food security and national seed industry security.The photosynthetic optimization is an important way to increase crop yield as well as an crucial pathway to improve crop resistance.Although some conceptional advances have been made in the field of photosynthetic improvement,there is still a lot of room for manipulation.This study raises the following provocative questions:（1）What are the differences in photosynthetic protein complexes from different types of crops?（2）how to improve the efficiency of light energy conversion in light reactions?（3）we aim to test the hypothesis that simultaneously manipulating the light and dark reactions can greatly improve the photosynthetic capacity?In this study,we performed analyses of the similarities and differences of photosynthetic protein complexes extracted from 9 representative crops at molecular level using Blue Native/BN-PAGE technology not only in diploid plants with the photosynthetic type of C₃,and in diploidy crops with the photosynthetic type of C₄,the dicot Cleome gynandra,and Moricandia suffruticosa with the photosynthetic type of C₃-C₄intermediacy,but also in polyploid crops.Furthermore,we screened 10candidate genes with high photosynthetic efficiency from the perspective of the regulatory factors of photosynthetic protein complexes based on these results.Overexpressed plants were generated using an Agrobacterium tumefaciens-mediated gene transfer system and homozygotes were identified.To Investigate preliminarily on the function of genes with high photosynthetic efficiency,we carried out experiments from the PSII activity and rapid fluorescence Induction kinetics,PSI complementary quantum yield,photosynthetic parameters,relative gene expression,and steady-state protein levels.The main results are as follows:（1）Using 9 representative crops,our data indicated that the photosynthetic complexes and their key subunits were dramatically distinct in terms of protein abundance and composition.We found that the content of PSII core protein D1 was higher in C_4,monocots and polyploid crops compared to C₃,dicots and diploid crops,respectively.Oryza Sativa had the highest amount of Cyt b₆fcomplex in all the crops examined here.In particular,the core subunit Cyt f of Cyt b₆f varies substantially.The abundance of PSI core subunit Psa A in Zea mays was remarkably higher relative to the other eight crops,with C₄being higher than C₃.Monocots contained significantly higher level of ATPase core subunit CF1βthan dicots.（2）For the screened gene Psb28 with high photosynthetic efficiency,compared with the wild type,the psb28 mutant has a pale-green and weak phenotype.Further research indicates that Psb28 affects function of PSII.An increased NPQ is due to a larger component of photoinhibitory quenching in the mutant and a decreased q L indicates a more oxidized plastoquinone pool in the mutant.After high light treatment,the Fv/Fm,ΦPSII and electron transfer rate of Psb28＿OE3-3 and Psb28＿OE40-19 are higher than those in the wild type.The chlorophyll fluorescence analyses demonstrate that Psb28 can affect the function of PSII.（3）Psb28 affects the electron transfer from Q_A to Q_B and overexpression of Psb28 can effectively improve the electron transfer from Q_A to Q_B under high light conditions.（4）Compared with the wild type,under the conditions of normal light,high light treatment for 1hour and high light treatment for 5.5 hours,[Y（I）]in the psb28 mutant was remarkablly lower than the wild type and overexpression materials,but the wild type and overexpression materials.There was no significant difference between WT and the expression families,indicating that Psb28 deficiency reduced PSI activity,but overexpression of Psb28 could not alleviate the photoinhibition of PSI in Arabidopsis by high light.（5）Compared with the wild type,under normal light,almost all photosynthetic complexes in the OE3-3 and OE40-19 overexpression lines had no significant difference,and the PSII complex was increased than the wild type treated with high light.2D BN/SDS-PAGE further shows that the change in the content of pigment protein complex is mainly attributed to change in the content of PSII core subunits.Compared with the wild type,the level of D1,CP43 and CP47 in the overexpression family increased after high light treatment,while the core subunit of PSI,PSI antenna,PSII antenna,Cyt b₆f,ATPase complexes and Rbc L content were relatively stable.Therefore,Psb28 protein mainly affects the content of PSII complex and its core subunits.The comparison of the differences in photosynthetic protein complexes between different plants and the preliminary investigation on genes modulating high photosynthetic efficiency here have important theoretical and practical value for improving photosynthetic traits of crops as well as augementing photosynthetic efficiency and facilitating stress resistance.