Transgenic Crop Research and Development Center, National Institute of Agrobiological Sciences, Tsukuba, Ibaraki 305-8602, Japan.
Plant Physiol. 2010 Dec;154(4):1842-54. doi: 10.1104/pp.110.164343. Epub 2010 Oct 12.
Rice (Oryza sativa) seed storage proteins (SSPs) are synthesized and deposited in storage organelles in the endosperm during seed maturation as a nitrogen source for germinating seedlings. We have generated glutelin, globulin, and prolamin knockdown lines and have examined their effects on seed quality. A reduction of one or a few SSP(s) was compensated for by increases in other SSPs at both the mRNA and protein levels. Especially, reduction of glutelins or sulfur-rich 10-kD prolamin levels was preferentially compensated by sulfur-poor or other sulfur-rich prolamins, respectively, indicating that sulfur-containing amino acids are involved in regulating SSP composition. Furthermore, a reduction in the levels of 13-kD prolamin resulted in enhancement of the total lysine content by 56% when compared with the wild type. This observation can be mainly accounted for by the increase in lysine-rich proteins. Although reducing the level of glutelins slightly decreased protein storage vacuoles (PSVs), the simultaneous reduction of glutelin and globulin levels altered the inner structure of PSVs, implicating globulin in framing PSV formation. Knock down of 13-kD prolamins not only reduced the size of endoplasmic reticulum-derived protein bodies (PBs) but also altered the rugged peripheral structure. In contrast, PBs became slightly smaller or unchanged by severe suppression of 10- or 16-kD prolamins, respectively, indicating that individual prolamins have distinct functions in the formation of PBs. Extreme increases or decreases in sulfur-poor prolamins resulted in the production of small PBs, suggesting that the ratio of individual prolamins is crucial for proper aggregation and folding of prolamins.
水稻种子贮藏蛋白（SSPs）在种子成熟过程中作为氮源在胚乳中合成并沉积在贮藏细胞器中。我们已经生成了谷蛋白、球蛋白和醇溶蛋白的敲低系，并研究了它们对种子质量的影响。一种或几种 SSP 的减少被 mRNA 和蛋白质水平上其他 SSP 的增加所补偿。特别是，谷蛋白或富含硫的 10-kD 醇溶蛋白水平的降低分别被含硫量低或其他富含硫的醇溶蛋白优先补偿，这表明含硫氨基酸参与调节 SSP 组成。此外，与野生型相比，13-kD 醇溶蛋白水平的降低导致总赖氨酸含量增加了 56%。这一观察结果主要归因于赖氨酸丰富蛋白的增加。虽然谷蛋白水平的轻微降低略微减少了蛋白质储存液泡（PSVs），但谷蛋白和球蛋白水平的同时降低改变了 PSVs 的内部结构，暗示球蛋白参与了 PSV 的形成。13-kD 醇溶蛋白的敲低不仅减少了内质网衍生的蛋白体（PBs）的大小，而且改变了 PB 粗糙的外围结构。相比之下，10-kD 或 16-kD 醇溶蛋白的严重抑制分别导致 PBs 略微变小或不变，表明单个醇溶蛋白在 PBs 的形成中具有不同的功能。含硫量低的醇溶蛋白的极度增加或减少导致了小 PBs 的产生，这表明单个醇溶蛋白的比例对于正确聚集和折叠醇溶蛋白至关重要。
