Wang Anqi, Cheng Qiao, Li Wenjia, Kan Mingxi, Zhang Yuxin, Meng Xiangbing, Guo Hongyan, Jing Yanhui, Chen Mingjiang, Liu Guifu, Wu Dianxing, Li Jiayang, Yu Hong
Key Laboratory of Seed Innovation, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing, China.
Yazhouwan National Laboratory, Sanya, China.
Plant Biotechnol J. 2025 Feb;23(2):480-488. doi: 10.1111/pbi.14511. Epub 2024 Nov 19.
Resistant starch (RS) is a special kind of starch with beneficial effects on obesity, type 2 diabetes and other chronic complications. Breeding high-RS rice varieties is considered a valuable way to improve public health. However, most rice cultivars only contain an RS level lower than 2% in cooked rice, and cloning of RS genes is critical to improve RS levels in rice. The loss of function of Starch Synthases IIIa (SSIIIa) and SSIIIb, two amylopectin biosynthetic genes, could elevate RS levels up to 10%. Here, we performed a systematic genetic study of 14 amylopectin biosynthetic genes in the ssIIIa ssIIIb double mutant via genome editing, and investigated their effects on RS formation, the eating quality and grain yield. The results showed that deficiency in SSIIa, SSIVb or ISA2 under the ssIIIa ssIIIb background could each elevate RS content to above 14%, and the quadruple mutants of sbeI sbeIIb ssIIIa ssIIIb and sbeI ssIVb ssIIIa ssIIIb could further increase RS levels to over 18%. Furthermore, the eating quality of cooked rice and grain yield decreased along with the elevated RS contents, showing a trade-off among these traits. In these mutants, ssIIIa ssIIIb showed the balanced performance of RS and grain yield. This study provides insights into RS biosynthesis with a series of RS genes in the amylopectin biosynthesis pathway and practical strategy to breed high-RS rice varieties with balanced performance.
抗性淀粉（RS）是一种对肥胖、2型糖尿病和其他慢性并发症具有有益作用的特殊淀粉。培育高RS含量的水稻品种被认为是改善公众健康的一种有价值的方法。然而，大多数水稻品种在煮熟的米饭中RS含量仅低于2%，克隆RS基因对于提高水稻中的RS含量至关重要。支链淀粉生物合成基因淀粉合酶IIIa（SSIIIa）和SSIIIb功能的丧失可使RS含量提高至10%。在此，我们通过基因组编辑对ssIIIa ssIIIb双突变体中的14个支链淀粉生物合成基因进行了系统的遗传学研究，并研究了它们对RS形成、食味品质和籽粒产量的影响。结果表明，在ssIIIa ssIIIb背景下，SSIIa、SSIVb或ISA2的缺失均可使RS含量提高到14%以上，sbeI sbeIIb ssIIIa ssIIIb和sbeI ssIVb ssIIIa ssIIIb的四重突变体可进一步将RS含量提高到18%以上。此外，随着RS含量的升高，米饭的食味品质和籽粒产量下降，表明这些性状之间存在权衡。在这些突变体中，ssIIIa ssIIIb在RS和籽粒产量方面表现出平衡的性能。本研究为支链淀粉生物合成途径中一系列RS基因的RS生物合成提供了见解，并为培育具有平衡性能的高RS水稻品种提供了实用策略。
