Rice (Oryza sativa L.) is an important food source and a primary source of high‐quality protein. Polyploid breeding is an effective approach to improving the nutritional quality of crops. Several stable tetraploid rice lines with both high seed setting rates and high protein content have been bred. In the present study, the protein quality of two tetraploid rice lines GD2‐4x and GD4‐4x with high protein content was analyzed in detail, and mechanisms associated with the high protein quality were explored from the perspective of endosperm structure. The results showed that the total protein content of GD2‐4x and GD4‐4x increased significantly by 40.27% and 35.15%, respectively, when compared to that of 9311‐2x (control). The content of each protein component also increased significantly, with a major increase being observed in glutelin content. The contents of 16 types of amino acids and total amino acids, as well as contents of nutrient limiting essential amino acids, such as lysine, threonine, and methionine, in tetraploid rice lines increased significantly when compared to those in the control. The thickness of the aleurone layer on the dorsal, lateral, and ventral positions of GD2‐4x and GD4‐4x seeds during different developmental days increased significantly when compared to that of 9311‐2x seeds. Amyloplasts were more regular and loosely arranged in GD2‐4x and GD4‐4x seeds. The tetraploid rice lines had higher total protein and amino acid contents, with glutelin accounting for the highest proportion of the increase. The tetraploid rice lines with high protein content had higher nutritional quality and value than the diploid rice line. The high protein quality of tetraploid rice lines could be associated with an increase in aleurone layer thickness, as well as changes in amyloplast morphology and distribution. This study demonstrates that polyploidization is an effective breeding approach to improving the nutritional quality and value of rice seeds. The results provide a theoretical basis for the utilization of tetraploid high protein rice lines and a reference for improving the nutritional quality of other crops.

中文翻译：

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胚乳结构的变化有助于在四倍体水稻中形成高质量的蛋白质


水稻 （Oryza sativa L.） 是一种重要的食物来源，也是优质蛋白质的主要来源。多倍体育种是提高作物营养质量的有效方法。已经培育了几种稳定的四倍体水稻品系，既有结实率又有高蛋白质含量。本研究详细分析了蛋白含量高的 GD2-4x 和 GD4-4x 两个四倍体水稻品系的蛋白品质，并从胚乳结构的角度探讨了与高蛋白品质相关的机制。结果表明，与 9311-2x （对照） 相比，GD2-4x 和 GD4-4x 的总蛋白含量分别显著增加了 40.27% 和 35.15%。每种蛋白质成分的含量也显著增加，其中谷蛋白含量显著增加。与对照相比，四倍体稻系中 16 种氨基酸和总氨基酸的含量，以及赖氨酸、苏氨酸和蛋氨酸等营养限制性必需氨基酸的含量显著增加。与 9311-2x 种子相比，GD2-4x 和 GD4-4x 种子在不同发育日背侧、侧侧和腹侧位置的糊粉层厚度显著增加。淀粉质体在 GD2-4x 和 GD4-4x 种子中更规则且排列松散。四倍体水稻品系总蛋白和氨基酸含量较高，其中谷蛋白占比最高。蛋白质含量高的四倍体水稻品系比二倍体水稻品系具有更高的营养品质和价值。 四倍体水稻品系的高蛋白质质量可能与糊粉层厚度的增加以及支链淀粉形态和分布的变化有关。这项研究表明，多倍体化是提高水稻种子营养质量和价值的有效育种方法。研究结果为四倍体高蛋白水稻品系的利用提供了理论依据，为提高其他作物的营养品质提供了参考。