Deficiency of Starch Synthase IIIa and IVb Alters Starch Granule Morphology from Polyhedral to Spherical in Rice Endosperm
Deficiency of Starch Synthase IIIa and IVb Alters Starch Granule Morphology from Polyhedral to Spherical in Rice Endosperm
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DOI：
10.1104/pp.15.01232
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发表时间：
2016-03-01
期刊：
影响因子：
7.4
通讯作者：
Fujita, Naoko
中科院分区：
文献类型：
--
作者：
Toyosawa, Yoshiko;Kawagoe, Yasushi;Fujita, Naoko
植物物种之间淀粉粒的形态差异显著。然而，控制淀粉粒形态的机制尚未阐明。水稻（Oryza sativa）胚乳产生具有特征的复合型淀粉粒，在一个造粉体中包含数十个多面体淀粉粒。一些其他谷类物种产生简单型淀粉粒，即每个造粉体中只有一个淀粉粒。一个缺乏淀粉合酶（SS）基因SSIIIa和SSIVb的双突变水稻（ss3a ss4b）产生球形淀粉粒，而亲本单突变体产生与野生型相似的多面体淀粉粒。ss3a ss4b造粉体在发育早期包含复合型淀粉粒，并且在随后的造粉体发育和种子脱水过程中球形淀粉粒彼此分离。对葡聚糖链长分布的分析确定了SSIIIa和SSIVb在支链淀粉链合成中具有重叠作用，聚合度为42或更高。对野生型发育中水稻种子的共聚焦荧光显微镜和免疫电子显微镜观察显示，大部分SSIVb定位在淀粉粒之间。因此，我们提出SSIIIa和SSIVb在决定淀粉粒形态以及维持造粉体包膜结构方面具有关键作用。我们提出了一个球形淀粉粒产生的模型。
Starch granule morphology differs markedly among plant species. However, the mechanisms controlling starch granule morphology have not been elucidated. Rice (Oryza sativa) endosperm produces characteristic compound-type granules containing dozens of polyhedral starch granules within an amyloplast. Some other cereal species produce simple-type granules, in which only one starch granule is present per amyloplast. A double mutant rice deficient in the starch synthase (SS) genes SSIIIa and SSIVb (ss3a ss4b) produced spherical starch granules, whereas the parental single mutants produced polyhedral starch granules similar to the wild type. The ss3a ss4b amyloplasts contained compound-type starch granules during early developmental stages, and spherical granules were separated from each other during subsequent amyloplast development and seed dehydration. Analysis of glucan chain length distribution identified overlapping roles for SSIIIa and SSIVb in amylopectin chain synthesis, with a degree of polymerization of 42 or greater. Confocal fluorescence microscopy and immunoelectron microscopy of wild-type developing rice seeds revealed that the majority of SSIVb was localized between starch granules. Therefore, we propose that SSIIIa and SSIVb have crucial roles in determining starch granule morphology and in maintaining the amyloplast envelope structure. We present a model of spherical starch granule production.