Wakayama Masataka, Ueno Osamu, Ohnishi Jun-Ichi
Department of Biochemistry and Molecular Biology, Faculty of Science, Saitama University, Saitama, 338-8570 Japan.
Plant Cell Physiol. 2003 Dec;44(12):1330-40. doi: 10.1093/pcp/pcg159.
The leaf of the NADP-malic enzyme type C(4) grass, Arundinella hirta, has not only mesophyll cells (MCs) and bundle sheath cells (BSCs, usual Kranz cells) but also another type of Kranz cells (distinctive cells; DCs) that are not associated with vascular bundles. We investigated photosynthetic enzyme accumulation along the base-to-tip maturation gradient of developing leaves by immunogold electron microscopy. In mature leaves, phosphoenolpyruvate carboxylase (PEPC) and ribulose 1,5-bisphosphate carboxylase/oxygenase (Rubisco) were detected in the MC cytosol and in the BSC and DC chloroplasts, respectively. Pyruvate, P(i) dikinase (PPDK) was present in the chloroplasts of all photosynthetic cells but with higher levels in the MCs. Rubisco was first detected in the basal region of emerging leaf blades where the BSCs and DCs became discernable. Subsequently, the accumulation of PEPC and PPDK was initiated in the region where the granal proliferation in the chloroplasts was conspicuous; and, suberized lamellae were formed in the cell walls of the Kranz cells. There was no difference in the patterns of cellular development and enzyme accumulation between the BSCs and DCs or between the MCs adjacent to each type of Kranz cells. These results demonstrate that, although the DCs are not associated with veins, they behaved like BSCs with respect to enzyme induction and cellular differentiation.
NADP - 苹果酸酶型C4禾本科植物野古草的叶片不仅含有叶肉细胞（MCs）和维管束鞘细胞（BSCs，即常见的花环细胞），还含有另一种不与维管束相连的花环细胞（特异细胞；DCs）。我们通过免疫金电子显微镜研究了发育叶片从基部到尖端成熟梯度上光合酶的积累情况。在成熟叶片中，磷酸烯醇式丙酮酸羧化酶（PEPC）和核酮糖 - 1,5 - 二磷酸羧化酶/加氧酶（Rubisco）分别在叶肉细胞胞质溶胶以及维管束鞘细胞和特异细胞的叶绿体中被检测到。丙酮酸，磷酸二激酶（PPDK）存在于所有光合细胞的叶绿体中，但在叶肉细胞中的含量更高。Rubisco最早在新出现叶片的基部区域被检测到，此时维管束鞘细胞和特异细胞开始变得明显。随后，PEPC和PPDK的积累在叶绿体基粒增殖明显的区域开始；并且，花环细胞的细胞壁中形成了栓质化片层。维管束鞘细胞和特异细胞之间或与每种花环细胞相邻的叶肉细胞之间在细胞发育和酶积累模式上没有差异。这些结果表明，尽管特异细胞不与叶脉相连，但在酶诱导和细胞分化方面它们的行为类似于维管束鞘细胞。
