• Seed weight is one of the most important agronomic traits in soybean for yield improvement and food production. Several quantitative trait loci (QTLs) associated with the trait have been identified in soybean. However, the genes underlying the QTLs and their functions remain largely unknown.
• Using forward genetic methods and CRISPR/Cas9 gene editing, we identified and characterized the role of GmKIX8‐1 in the control of organ size in soybean.
• GmKIX8‐1 belongs to a family of KIX domain‐containing proteins that negatively regulate cell proliferation in plants. Consistent with this predicted function, we found that loss‐of‐function GmKIX8‐1 mutants showed a significant increase in the size of aerial plant organs, such as seeds and leaves. Likewise, the increase in organ size is due to increased cell proliferation, rather than cell expansion, and increased expression of CYCLIN D3;1‐10.
• Lastly, molecular analysis of soybean germplasms harboring the qSw17‐1 QTL for the big‐seeded phenotype indicated that reduced expression of GmKIX8‐1 is the genetic basis of the qSw17‐1 phenotype.

中文翻译：

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GmKIX8-1 调节大豆器官大小，是主要种子重量 QTL qSw17-1 的致病基因。

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  种子重量是大豆对提高产量和粮食生产最重要的农艺性状之一。已在大豆中鉴定出与该性状相关的几个数量性状基因座（QTL）。然而，QTL 背后的基因及其功能仍然很大程度上未知。
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  使用正向遗传方法和 CRISPR/Cas9 基因编辑，我们鉴定并表征了 GmKIX8-1 在控制大豆器官大小中的作用。
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  GmKIX8-1 属于含有 KIX 结构域的蛋白质家族，可负向调节植物细胞增殖。与这一预测的功能一致，我们发现功能丧失的 GmKIX8-1 突变体表现出气生植物器官（例如种子和叶子）的大小显着增加。同样，器官大小的增加是由于细胞增殖增加，而不是细胞扩张，以及CYCLIN D3;1-10表达增加。
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  最后，对含有大粒表型qSw17-1 QTL 的大豆种质进行分子分析表明， GmKIX8-1表达减少是qSw17-1表型的遗传基础。