转C4光合基因水稻及其在育种中的应用

按光合作用途径可将植物分为C3植物、C4植物和CAM植物，由于C4植物在高光强、高温和高氧分压的条件下，比C3植物具有较高的光合效率，作物生理和育种学家就试图用C4光合途径改造C3作物，以提高主要农作物如稻、麦和大豆等光合生产力，但通过常规杂交的方法难以奏效。近年来，随着分子生物学的兴起和植物转基因技术的快速发展，许多与C4光合作用途径相关的关键酶PEPC、NADP-苹果酸(NADP—ME)和PPDK等一系列基因已从玉米、高粱和苋菜等C4植物中被克隆，对这些基因启动子序列分离、重组、转化及表达的研究，发现它们可以在C3植物中驱动外源基因并进行组织特异性表达，而且一系列C4型光合基因导入C3植物的成功报道。特别是获得高表达的转C4光合基因水稻，表现光合能力和种子产量显著提高，而且在光逆境的条件下，超氧化物歧化酶(SOD)和过氧化物酶(POD)的活性提高，从而有效地清除活性氧分子，表现耐光抑制(氧化)等。目前利用转C4光合基因水稻的育种研究也取得了重要进展，培育出携带C4光合基因的高光效水稻株系，在遗传上证明了常规育种和生物技术结合可以将转C4光合基因水稻中高表达的C4光合基因遗传给后代，获得高光效的超级稻，最后提出了本研究中尚需深入研究的问题。

Transgenic Rice Overexpressing C4 Photosynthetic Genes and Their Application in Breeding

According to photosynthetic pathways, plants can be divided into three types such as C3 plant, C4 plant and CAM plant. Due to the CO2 concentration mechanism, C4 plants exhibited higher photosynthetic efficiency than C3 plant under the condition of high light intensity, high temperature and high oxygen partial pressure conditions. Crop physiologist and breeder try to enhance C4 photosynthetic capability in C3 plants such as rice, wheat and soybean to increase the photosynthetic productivity. But the conventional hybridization in the same family such as that between C4 plant (maize) and C3 plant (rice) can still not bring into effect. In recent years, with the rapid development of molecular biology and transgenic technology, many genes encoding key C4 photosynthesis enzymes derived from maize, sorghum and amaranth, were isolated, cloned, recombined and expressed. These are phosphoenolpyruvate carboxylase (PEPC), private orthophosphate dikinase (PPDK), and NADP-malic enzyme (NADP-ME). The research on the promoter of these genes showed that they can promote foreign gene expressing at special tissues of C3 plant. Furthermore, many transgenic rice plants overexpressing C4 photosynthetic genes have obtained successfully. In peculiar, PEPC transgenic rice exhibited a higher photosynthetic capability and grain yield of a plant. Under photo-stress conditions, the activity of SOD and POD in PEPC transgenic rice plants also enhanced, which is beneficial to get rid to the active oxygen species and exhibiting tolerance to photoinhibition (photooxidation). At present, there was important progress in the application on C4 transgenic rice in breeding. Some rice lines with high efficiency derived from C4 photosynthesis gene transgenic rice plants have been obtained. The research also proved in genetics that transgenic rice plants overexpressing C4 photosynthesis genes can transfer to its generation with high efficiency and high grain yield by combination convention breeding and biotechnology. At last, the problems need to be studied were also put forward to.