C_4转基因水稻秧苗叶片气孔与叶鞘维管束结构特征

Structure Characteristics of Stomata in Leaves and Vascular Bundles in Culms of Transgenic Rice Expressing C4 Photosynthesis Enzymes

目的探明C4转基因水稻高光效的生物学结构基础。方法以已导入玉米C4光合关键酶磷酸烯醇式丙酮酸羧化酶(PEPC)、丙酮酸磷酸二激酶(PPDK)、NADP-苹果酸酶(NADP-ME)和PEPC+PPDK的转基因水稻为材料,以其受体品种Kitaake(WT)为对照,运用扫描电镜观察了秧苗叶片气孔与叶鞘维管束结构,运用透射电镜观察叶肉细胞。结果与对照品种相比,转C4单基因水稻叶片气孔密度提高、面积增大,PPDK气孔密度和气孔面积都居各转基因品系之首;转C4双聚合基因(PEPC+PPDK)水稻叶片气孔密度提高、面积减小;C4转基因水稻各品系叶片叶肉细胞中叶绿体基粒堆密集,有些基粒类囊体沿长轴方向排列整齐、完整;C4转基因品系的叶鞘均比对照品种粗壮坚韧;除PPDK外,所有转基因品系叶鞘的内外侧维管束及其导管管腔、筛管等执行物质运输功能的组织结构的面积均大于对照品种。结论C4转基因水稻叶片气孔多、面积大以及叶鞘维管束结构发达是C4转基因水稻高光效实现的结构前提和基础,与秧苗高的干物质积累相一致。

[Objective] The aim of this study is to discover the biological structure basis of transgenic rice expressing C4 photosynthesis enzymes and photosynthesizing highly and efficiently. [Method] Using four transgenic rice lines over-expressing maize photosynthesis enzymes of phosphoenolpyruvate carboxylase （PEPC）, pyruvate, othophosphate dikinase （PPDK）, PEPC ＋ PPDK, and rice nicotinamide adenine dinucleotide phosphate-malic enzyme （NADP-ME） as materials, and an untransformed wild type Kitaake as the control, the structures of stomata in leaves and vascular bundles in culms of the seedlings were observed with a scanning electron microscope and mesophyll cells were observed with a transmission electron microscope. [Result] Compared with the control, the density and the area of the stomata in leaves of the transgenic rice lines were greater, with the PPDK line greatest among the four lines. The d sity of stomata in the leaves of transgenic rice with two polymerizing genes （PEPC ＋ PPDK） was increased, but the area of stomata was reduced. The stacking degree of chloroplast thylakoids in mesophyll cells was denser, and some thylakoids were arranged more orderly along the long axis of chloroplast for the transgenic rice lines than those for the WT. The transgenic rice lines exhibited thicker and stronger culms as compared to WT. Except for PPDK, all the transgenic rice lines had larger areas of the tissue structure performing substance-transporting function, such as the outer and inner vascular bundles and their catheter and sieve tubes in culms, as compared with WT. [Conclusion] More number and larger area of stomata in leaves and more developed vascular bundles in culms of C4 transgenic rice lines, all these structure characteristics were the basis of its＇ photosynthesizing highly and efficiently, and closely associated with the greater dry matter accumulation of seedlings.