Main conclusionA novel allele of the sugary-1 rice mutant was isolated. The single amino acid change led to isoamylase activity reduction and accumulation of high-molecular-weight phytoglycogen in seeds.AbstractA new sugary rice variety with an improved seed appearance has been isolated and designated Hemisugary1. This mutant, which was derived from Japonica-type cultivar Tsugaruroman treated with sodium azide, has about half the isoamylase activity of seeds in the original Tsugaruroman. The mutant also accumulates significant phytoglycogen, albeit approximately 40% of the total phytoglycogen in the existing sugary cultivar Ayunohikari which is defective in its most isoamylase activity. The site of mutation was identified using a re-sequence of the whole genome and a cleaved amplified polymorphic sequence (CAPS) marker. The hemisugary phenotypes of the F2 progeny were entirely consistent with the results of genotyping using the CAPS marker. Segregation analysis of the F2 population showed that the hemisugary phenotype was controlled by a single recessive gene, which was produced by a G → A single nucleotide polymorphism in the sugary-1 gene, resulting in a missense mutation from glycine to aspartic acid at amino acid position 333. Zymogram showed that this amino acid replacement resulted in a decrease in isoamylase activity with a concomitant reduction in the formation of isoamylase complexes. Phytoglycogen molecules from Hemisugary1 seeds were 3.5 times larger and contained more short glucan chains than did Ayunohikari seeds. Our data provide new insights into the relationship between isoamylase structure and phytoglycogen formation.

中文翻译：

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一种新的含糖型水稻突变体 Hemisugary1 的生化分析，该突变体携带一个新的含糖 1 基因等位基因

主要结论分离到一个新的sugary-1水稻突变体等位基因。单个氨基酸的变化导致异淀粉酶活性降低和高分子量植物糖原在种子中的积累。 摘要：已分离出具有改良种子外观的含糖水稻新品种并命名为Hemisugary1。该突变体来源于经叠氮化钠处理的粳稻品种津轻鲁曼，其异淀粉酶活性约为原始津轻鲁曼种子的一半。该突变体还积累了大量的植物糖原，尽管在其大部分异淀粉酶活性存在缺陷的现有含糖品种 Ayunohikari 中约占总植物糖原的 40%。使用全基因组的重测序和切割的扩增多态性序列 (CAPS) 标记物鉴定突变位点。F2 后代的半糖表型与使用 CAPS 标记的基因分型结果完全一致。F2群体的分离分析表明，半糖表型由单个隐性基因控制，该隐性基因由sugary-1基因中的G→A单核苷酸多态性产生，导致氨基酸处从甘氨酸到天冬氨酸的错义突变位置 333。酶谱显示，这种氨基酸置换导致异淀粉酶活性降低，同时异淀粉酶复合物的形成减少。来自 Hemisugary1 种子的植物糖原分子比 Ayunohikari 种子大 3.5 倍，并且含有更多的短葡聚糖链。我们的数据为异淀粉酶结构与植物糖原形成之间的关系提供了新的见解。