C₄Syndrome Genetic And Development Mechanism

About forty million years ago, the concentration of CO2on the earth droppeddown sharply. With the change, C4photosynthesis, a new type of photosynthesisemerged. Unlike C3photosynthesis, C4photosynthesis fixes CO2from the atmospherefor a four carbon compounds in mesophyll cells. Then this four carbon compoundswill be transfered to the bundle sheath cells for decarboxylation. The CO2releasedfrom the four carbon compounds will be refixed into the Calvin cycle by Rubisco. Inthis process, CO2is further concentrated, leading to the high CO2concentrationaround Rubisco. It inhibits the photorespiration effectively, and improves the rate ofphotosynthesis, so that the biomass of C4crop is higher than the common C3crops.Therefore C4pathway has been the research focus in recent years.Accompanied by the emergence of C4photosynthesis, C4plants have manyobvious different traits, such as leaf anatomical structure, physiological andbiochemical processes and the quantitative expression of genes etc. A series of suchcharacters appearing along with C4photosynthesis are referred as C4syndrome.In higher plants, there are some generas including C3, C4and C3-C4types. Mostresearches about the C4syndrome were carried out in the species that have closegenetic relationship and different photosynthesis types. C4syndrome is a combinationof series of complex traits. We have had a fundamental understanding about thebiochemical process of C4cycle, but the efficient C4photosynthesis genes andproteins have not been well known. All the transport proteins that ensure the highmetabolic flux inside and outside cells, have not been identified completely. And thegenes that controlling and maintaining the structure change in all cells and leaves alsohave not been identified completely. Consequently the researches about C4don’t haveevident achievement.We use Haloxylon ammodendron and Salsola passerina as the materials to studyC4syndrome. Both Haloxylon ammodendron and Salsola passerinai have cotyledon which conducts C3pathway, and leaves that conduct C4pathway. In terms of leafanatomical structure, Paraffin section was made to observe the anatomical structuresof different photosynthetic organs, we confirmed different organs have differentphotosynthesis pathway. In the aspect of the determination of δ13C values, wemeasured the δ13C values about the cotyledon and leaves of the two experimentalplants in different development stage. Then we made a new interpretation, combingthe δ13C values with plant development. In genes different expression, thetranscriptome analysis about cotyledon and assimilating shoots taken from Haloxylonammodendron was performed, eliminating the differences between different species.We identified and found a large number of C4syndrome related genes andtranscription factors. Besides, we made flow cytometry analysis of Salsola passerinausing the genome of Arabidopsis thaliana as a reference. So the genome size ofSalsola passerina was roughly estimated. This result laid a foundation for the Salsolapasserina whole genome sequencing.CO2has a very big influence on the photosynthesis of plants. Plants underdifferent concentrations of CO2will show different properties. Ginkgo, a kind of fossilplants, survived very well during the period of CO2concentration reduction, so it hasan important research value. In this paper, we cultivated ginkgo seedlings in threedifferent CO2concentrations respectively, which showed that ginkgo seedlings underdifferent CO2concentration got different characters. We tried to find the connectionbetween these traits and the photosynthesis transformation from C3to C4.