Study On Photosynthetic Characteristics Of Different Plants And Prokaryotic Expression Of C₄Key Enzyme Genes In Amaranthus Hypochondriacus L

C4plant has higher photosynthetic efficiency and bio-yield in extreme conditions such as high temperature, strong light and drought because of "CO2pump"concentrating mechanism. Using genetic engineering to clone the key enzyme genes of C4photosynthetic pathway and transfer them to C3plant would improve photosynthetic efficiency, enhance adaptability to harsh environments and increase production of C3plant. This study focused on photosynthetic characteristics of different plants, including C4and C3plants, dicotyledonous and monocotyledonous plants, in order to reveal rules of photosynthesis of different plants and provide excellent candidate materials for transgenic use. And the copies of PEPC gene in Amaranthus hypochondriacus L, a dicotyledonous C4plant, were detected by Southern blot. Both PEPC gene and NAD-ME gene were cloned and recombined into the prokaryotic expressing vectors and correctly expressed.1. The photosynthesis characteristics of Amaranthus hypochondriacus L with Zea mays (maize) and Nicotiana tobacum were compared. It was showed that Pn of C4plants including dicotyledonous Amaranthus hypochondriacus L and monocotyledonous maize was higher than C3dicotyledonous Nicotiana tobacum under the test condition. The Pn was positively related to PAR in the three plants and Pn of both Amaranthus hypochondriacus and maize was positively related to temperature between20-40℃. The Pn of Nicotiana tobacum was positively related to temperature between15-30℃and negatively related to temperature between30-40℃.2. Genomic DNA of Amaranthus hypochondriacus was extracted and digested by a variety of restriction endonuclease, electrophoresised on0.7%gel, transferred into nylon membrane. DIG labeling PEPC gene was random primed labeled with DIGS as probe and labeling efficiency was determined. The results of Southern blot showed that the genome of Amaranthus hypochondriacu harboured three copies of PEPC genes.3. The cDNA of PEPC gene and NAD-ME gene of Amaranthus hypochondriacu were amplified by PCR. The length of PEPC gene was2895bp, which encoded964amino acids. The length of NAD-ME gene was1872bp, which encoded623amino acids. The sequences of two genes showed100%homology with the source sequences (Genbank accessions were HQ186302and HQ186303respectively). The Prokaryotic expression vectors pEASY-E1-ME and pEASY-E1-PEPC are successfully constructed.After induced by1mmol/L IPTG for2h、4h and6h respectively under30℃, the transetta(DE3) strains harbouring prokaryotic expression vector pEASY-E1-ME and pEASY-E1-PEPC respectively expressed efficiently the target proteins.