The Screening Of The Rice Material With Maize Pepc Gene Y MAS And The Analyzing Of Pepc Gene Effects

It has been hotspot that the breeding of high photosynthetic efficiency rice using C₄-type high photosynthetic genes since the successing of introducing the maize pepc gene to Kitaake by genetic engineering technology. People expected to gain theories and methods of the breeding of high photosynthetic efficiency rice and finally to gain high yield varieties of rice. It was screened for the transformant rice by MAS and got the Shuhui881 with maize pepc gene. Meanwhile, the genetic background of Shuhui881 with maize pepc gene was analyzed. The dynamics of photosynthetic characteristics in leaves of transgenic rice plants with maize pepc gene and control were determined at initial- tillering stage, full- tillering stage, jointing stage, begin-heading stage, heading stage, maturing stage and six different growing stages of flag leaves. The effects of maize pepc gene were analyzed under different genetic background. The main results were as follows:1. The transformant rice and the Shuhui881 with maize pepc gene were correctly screened by MAS using the characteristic primers of the maize pepc gene, which was designed by BLAST. The technological system for selecting high photosynthetic efficiency rice has been established. It includes molecular marker assisted-selection by the characteristic primers of C4-type pepc gene, and the determination of PEPCase activity and net photosynthesis rates (Pn), and the investigation of plant performance in field.2. The genetic background of 10 improved plants of Shuhui881 with maize C₄-type pepc gene were analyzed by 530 pairs SSR primers. There were only 1-4 differential SSR loci compared with Shuhui 881. The similarities of genetic background were 95.15%-99.03%. The results showed that the genetic background of Shuhui881 with maize C₄-type pepc gene almost were same as Shuhui881 by MAS.3. The dynamic analysis of photosynthetic characteristics in leaves of the transformant rice at six different growing stages and different growing of flag leaves were carried. The results indicated that the expressed levels of PEPCase activity were notable higher than that of untransformed rice at the six different developmental stages. The highest expressed levels of PEPCase activity was at jointing stage and the lowest was at maturing stage, The largest value of increase was at heading stage and the least value was at maturing stage. The net photosynthetic rates (Pn) of the transformant rice averagely increased 18.02%. Itwas higher than that of untransformed rice, Kitaake except initial- tillering stage. The highest Pn was begin-heading stage.The largest increased value was 38.26% at begin-heading stage. Both the PEPCase activity and the net photosynthesis rates of flag leaves of the transformant rice were higher than Kitaake at different growing stage. All indicated that the pepc gene could be expressed at six different growing stages of rice and different growing of flag leaves.4. The dynamic analysis of photosynthetic characteristics in leaves of Shuhui881 with the maize CHype pepc gene was carried at six different growing stages of rice and at different growing stage of flag leaves. It showed that the expressed levels of PEPCase activities of improved Shuhui 881 plants with pepc gene were higher than Shuhui 881 at the six different developmental stages. The highest expressed level of PEPCase activity was at jointing stage(1264.2 umolPEPmg'1chlh"1) and the largest increased value of PEPCase activity of improved Shuhui 881 with maize C4-type pepc gene was 23.3-fold than Shuhui 881 at initial- tillering stage. The net photosynthetic rates (Pn) of improved Shuhui881 with maize C4-type pepc gene were increased at initial- tillering stage, full- tillering stage, jointing stage and begin-heading stage. The largest value of the net photosynthesis rates (Pn) increased was 22.3% at jointing stage. The PEPCase activity and the net photosynthesis rates of flag leaves of Shuhui881 with pepc gene all were higher than Shuhui881 at different growing stages of flag leaves. The values of PEPCase activity and the net photosynthesis rates (Pn) of flag leaf from complete outspreading to 28* d arrived at the biggest. All these proved that the maize C4-type pepc gene was not only inherited but also highly expressed in new genetic background.5. It was found that the highest of PEPCase activity and the net photosynthesis rates (Pn) of leaf at jointing stage. Therefore, it would be better for determining photosynthetic characteristics at this growing stage.6. Light response curves and CO2 response curves of transgenic rice plants and Shuhui881 with pepc gene were determined. The results indicated that light saturated point, photosynthetic quantum yield, and carboxylation efficiency of transgenic rice all were improved compared with untransformed rice and CO2 compensation point was reduced. Photosynthetic quantum yield and carboxylation efficiency of the transformant rice were increased by 6.8%, 28.13% and Shuhui881 with maize pepc gene were increased by 105.2% and 4.3%, respectively. It indicated that the maize pepc gene was introduced to rice could improve its use efficiency of light and assimilating ability of CO2.7. The effect of maize C4-type pepc gene was studied using the Fi,which was established by1 Kitaake with maize C4-type pepc gene were crossed with four different cytoplastic retainer. It showed that PEPCase activity were highly expressed and the net photosynthesisrates increased to some extent, but it was complex to characters of yield. The increased trends of efficient panicle and 103-grain weight and seed setting rate,but the reduced trends of panicle length and total grains per panicle,yield potential per plant changed differently because of different cytoplastic.8. The effects of pepc gene between indica and japonica were compared. The plant height of transgenic rice plants was shortened and efficient panicle were increased. Other characters of yield were changed differently. There was only a little affection to seed structure of length, breadth and thickness.There probably was a higher effect of pepc gene in japonica than in indica.9. The test of photoinhibition indicated the transformant rice' s capacity of tolerance to photoinhibition and photooxidation was higher than Kitaake' s. The tolerant ability of Shuhui881 with pepc gene to photoinhibition and photooxidation was improved distinctly, compared with Shuhui881.