Cai Yue, Chen Haiyuan, Xiao Ning, Wu Yunyu, Yu Ling, Chen Zichun, Liu Jianju, Shi Wei, Pan Cunhong, Li Yuhong, Zhou Changhai, Ji Hongjuan, Huang Niansheng, Zhang Xiaoxiang, Zhang Yunhui, Li Aihong
Lixiahe Agricultural Research Institute of Jiangsu Province, Yangzhou, 225007, China; Yangzhou University, Yangzhou, 225009, China.
Provincial Key Laboratory of Agrobiology, Institute of Germplasm Resources and Biotechnology, Jiangsu Academy of Agricultural Sciences, Nanjing, China.
J Plant Physiol. 2022 Mar;270:153638. doi: 10.1016/j.jplph.2022.153638. Epub 2022 Feb 6.
The amyloplast is a specialized plastid in rice endosperm cells where starch is synthesized and stored as starch granules (SGs). However, little is known about the molecular mechanism underlying amyloplast and SG development. In this study, a novel mutant (c134) demonstrating a floury endosperm with enlarged SGs and amyloplasts was identified. The floury endosperm was caused by rounder, loosely packed SG. Grain-quality profile and expression analysis showed reduced contents of total starch and amylose in the c134 mutant, as well as reduced expression of a number of genes involved in starch biosynthesis. Galactosyldiacylglycerol (GDG) content and fatty acid synthesis play important roles in plastid development, and in the c134 endosperm, an obvious decrease in GDG and various fatty acids was observed, with down-regulated expression of various genes involved in lipid biosynthesis. Furthermore, map-based cloning revealed an amino acid substitution (glycine to aspartic acid) in the substandard starch grain4 (SSG4) protein. The results of this study suggest that SSG4 influences the regulation of starch and lipid metabolism as well as amyloplast development, a finding that is useful for potential genetic improvement of rice grain quality in future starch and lipid breeding and biotechnology.
造粉体是水稻胚乳细胞中的一种特殊质体，淀粉在其中合成并以淀粉粒（SGs）的形式储存。然而，关于造粉体和淀粉粒发育的分子机制知之甚少。在本研究中，鉴定出一个新的突变体（c134），其表现出粉质胚乳，淀粉粒和造粉体增大。粉质胚乳是由更圆、堆积松散的淀粉粒引起的。谷物品质分析和表达分析表明，c134突变体中总淀粉和直链淀粉含量降低，以及一些参与淀粉生物合成的基因表达降低。半乳糖基二酰甘油（GDG）含量和脂肪酸合成在质体发育中起重要作用，在c134胚乳中，观察到GDG和各种脂肪酸明显减少，参与脂质生物合成的各种基因表达下调。此外，图位克隆揭示了次等淀粉粒4（SSG4）蛋白中的一个氨基酸取代（甘氨酸到天冬氨酸）。本研究结果表明，SSG4影响淀粉和脂质代谢的调控以及造粉体的发育，这一发现有助于未来淀粉和脂质育种及生物技术中水稻籽粒品质的潜在遗传改良。
