| Summary: | 碩士 === 國立中興大學 === 植物學系 === 90 === Three C4 photosynthetic genes of maize, ppc, pdk and Me-2 were constructed and introduced into rice (Oryza sativa. var Kitaake) using Agrobacterium-mediated transformation system. Two lots of T6-PEPC (k2, k3), T4-PPDK (k4, k5) and T4-NADP-ME (k6, k7) rice seeds were obtained as single gene transformants, while 3 lots of T3-PEPC/PPDK as hybrid transformants (k8, k9, k10). Rice seedings were planted in Wagner’s pots(1/5000 a) in green house. The 3rd fully-expanded leaves were used for assaying enzyme activities.
Transgenic rice plants showed higher enzyme activities than that of untransformed line. In k9 line, the PEPC activity increased 15-fold over that of untransformed line. G6P provided protection against malate inhibition of PEPC in ppc gene transgenic rice plants. Gas exchange measurements of flag leaves of transgenic rice plants showed that there were no significant difference in photosynthetic rates among transgenic lines. The light saturation point, transpiration rate and stomatal conductance of the lines with higher PEPC-activity were higher than untransformed line. The relationship between the gas exchange measurements and the enzyme activities of transgenic rice plants showed that PEPC-activity had a positive correlation with transpiration rate and stomatal conductance. The relationship between the tassel weight and gas exchange measurements showed that tassel weight had a positive correlation with transpiration rate and stomatal conductance of rice plants. The relationship between PEPC-activities and the tassel weight of transgenic rice plants showed that PEPC-activities had a positive correlation with the tassel weight of transgenic rice plants. The activities of PPDK and NADP-ME showed no significant difference among transgenic rice plants. The carbon isotope composition of leaf tissue of transgenic rice plants showed that all transgenic lines were still assimilating CO2 by C3-photosynthesis.
These results suggest that introducing the intact C4-photosynthetic gene into rice can increase the activities of C4- photosynthetic enzymes in rice plants, and the raising of PEPC-activity in rice plants can enhance the stomatal conductance and promote the yield of rice plants. In this experiment, we have selected some transgenic rice plants with high PEPC-activity, high stomatal conductance or high yield, and will keep their seeds for future studies.
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