SummaryGrain chalkiness is an undesirable trait that negatively regulates grain yield and quality in rice. However, the regulatory mechanism underlying chalkiness is complex and remains unclear. We identified a positive regulator of white‐belly rate (WBR). The WBR7 gene encodes sucrose synthase 3 (SUS3). A weak functional allele of WBR7 is beneficial in increasing grain yield and quality. During the domestication of indica rice, a functional G/A variation in the coding region of WBR7 resulted in an E541K amino acid substitution in the GT‐4 glycosyltransferase domain, leading to a significant decrease in decomposition activity of WBR7A (allele in cultivar Jin23B) compared with WBR7G (allele in cultivar Beilu130). The NIL(J23B) and knockout line NIL(BL130)KO exhibited lower WBR7 decomposition activity than that of NIL(BL130) and NIL(J23B)COM, resulting in less sucrose decomposition and metabolism in the conducting organs. This caused more sucrose transportation to the endosperm, enhancing the synthesis of storage components in the endosperm and leading to decreased WBR. More sucrose was also transported to the anthers, providing sufficient substrate and energy supply for pollen maturation and germination, ultimately leading to an increase rate of seed setting and increased grain yield. Our findings elucidate a mechanism for enhancing rice yield and quality by modulating sucrose metabolism and allocation, and provides a valuable allele for improved rice quality.

中文翻译：

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WBR7 的自然变异通过调节库器官中的蔗糖供应赋予水稻高产和优质


摘要谷物垩白是一种不良性状，会对水稻产量和品质产生负面影响。然而，白垩质的调节机制很复杂且仍不清楚。我们发现了白腹率（WBR）的正调节因子。 WBR7 基因编码蔗糖合酶 3 (SUS3)。 WBR7 的弱功能等位基因有利于提高谷物产量和质量。在籼稻驯化过程中，WBR7编码区的功能性G/A变异导致GT-4糖基转移酶结构域中E541K氨基酸取代，导致WBR7A（品种Jin23B中的等位基因）分解活性显着降低与WBR7G（品种北路130等位基因）相比。 NIL(J23B)和敲除系NIL(BL130)KO表现出比NIL(BL130)和NIL(J23B)COM更低的WBR7分解活性，导致传导器官中蔗糖分解和代谢更少。这导致更多的蔗糖运输到胚乳，增强了胚乳中储存成分的合成并导致WBR降低。更多的蔗糖也被输送到花药，为花粉成熟和发芽提供充足的基质和能量供应，最终导致结籽率提高和谷物产量增加。我们的研究结果阐明了通过调节蔗糖代谢和分配来提高水稻产量和品质的机制，并为改善水稻品质提供了有价值的等位基因。