Institute of Plant Science and Resources, Okayama University, Kurashiki, 710-0046, Japan.
Sci Rep. 2019 Mar 6;9(1):3745. doi: 10.1038/s41598-019-40424-w.
Amyloplasts are plant-specific organelles responsible for starch biosynthesis and storage. Inside amyloplasts, starch forms insoluble particles, referred to as starch grains (SGs). SG morphology differs between species and SG morphology is particularly diverse in the endosperm of Poaceae plants, such as rice (Oryza sativa) and barley (Hordeum vulgare), which form compound SGs and simple SGs, respectively. SG morphology has been extensively imaged, but the comparative imaging of amyloplast morphology has been limited. In this study, SG-containing amyloplasts in the developing endosperm were visualized using stable transgenic barley and rice lines expressing amyloplast stroma-targeted green fluorescent protein fused to the transit peptide (TP) of granule-bound starch synthase I (TP-GFP). The TP-GFP barley and rice plants had elongated amyloplasts containing multiple SGs, with constrictions between the SGs. In barley, some amyloplasts were connected by narrow protrusions extending from their surfaces. Transgenic rice lines producing amyloplast membrane-localized SUBSTANDARD STARCH GRAIN6 (SSG6)-GFP were used to demonstrate that the developing amyloplasts contained multiple compound SGs. TP-GFP barley can be used to visualize the chloroplasts in leaves and other plastids in pollen and root in addition to the endosperm, therefore it provides as a useful tool to observe diverse plastids.
淀粉体是植物特有的细胞器，负责淀粉的生物合成和储存。在淀粉体内部，淀粉形成不溶性颗粒，称为淀粉粒（SG）。SG 的形态在不同物种之间存在差异，禾本科植物（如水稻和大麦）的胚乳中 SG 形态尤其多样，分别形成复合 SG 和简单 SG。SG 的形态已被广泛成像，但淀粉体形态的比较成像受到限制。在这项研究中，通过表达与颗粒结合型淀粉合成酶 I 的转运肽（TP）融合的淀粉体基质靶向绿色荧光蛋白的稳定转基因大麦和水稻系，可视化了发育中的胚乳中含有 SG 的淀粉体。TP-GFP 大麦和水稻植物的淀粉体含有多个 SG，并在 SG 之间有缢痕。在大麦中，一些淀粉体通过从其表面伸出的狭窄突起连接。使用产生定位于淀粉体膜的 SUBSTANDARD STARCH GRAIN6（SSG6）-GFP 的转基因水稻系来证明发育中的淀粉体包含多个复合 SG。TP-GFP 大麦除了胚乳之外，还可以用于可视化叶片中的叶绿体以及花粉和根中的其他质体，因此它是观察各种质体的有用工具。
