PARENT SESSION
Posters P6D Crop photosynthesis, agricultural biotechnology. Abstracts (742-753)

Photoprotection effects in transgenic rice of C₄ phosphoenopyruvate carboxylase and its application in breeding. Demao Jiao^*,1, Behua JI², Xia Li³, ¹ Zhongling Street 50, Nanjing, Jiangsu Province, China² Zhongling Street 50, Nanjing, Jiangsu Province, China³ Zhongling Street 50, Nanjing, Jiangsu Province, China

ABSTRACT- With untransformed rice variety kitaake as control, the characteristics of carbon assimilation and photoprotection in PEPC transgenic rice were studied in this paper. Results demonstrated that the PEPC activity in untransformed rice was low, but the activity was induced under high light or photoinhibition condition. PEPC in untransformed rice contributed about 5-10% to photosynthesis, as shown by the application of the specific inhibitor DCDP. When maize PEPC gene was introduced into rice, transgenic rice expressed high level of maize PEPC protein and had high PEPC activity. Simultaneously, the activity of CA transporting CO₂ increased significantly. So the photosynthetic capacity increased greatly (50%) under higher CO₂ supply. Under CO₂ free condition, CO₂ release in leaf was less, the value of ₁₃C in PEPC transgenic rice was similar to that in untransformed rice, demonstrating that transgenic rice is still C₃ plants. During a pulse-chase experiment under high light, the label in PEPC transgenic rice was distributed more in asparate, indicating that a limiting C₄ cycle exists in leaf of transgenic rice. In addition, the introduction of maize PEPC gene could activate or induce activities of the key enzymes scavenging active oxygen, such as SOD, POD. So higher PSII photochemical efficiency and lower O₂ generation and MDA content under photoinhibition condition could improve protection from photoxidation. A PEPC transgenic rice line as a male parent crossed with a Japonica rice cultivar 9516, then the anther of the F₁ hybrids were cultured. The photosynthetic rate and the yield per plant of one line was higher than the control 9516. It suggested that the combining conventional hybrid with anther culture be utilized in quickly transferring the maize PEPC gene into the rice genome.

KEY WORDS: PEPC gene , breeding, rice, photoprotect