Key Laboratory of Plant Molecular Physiology, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China.
University of Chinese Academy of Sciences, Beijing 100049, China.
J Exp Bot. 2022 Nov 2;73(19):6942-6954. doi: 10.1093/jxb/erac330.
Head rice yield (HRY) is an essential quality trait, and is sensitive to environmental stresses during the grain-filling, harvest, and postharvest stages. It is therefore important for rice production and global food security to select for superior HRY traits; however, the molecular basis of this trait remains unknown. Using diverse rice germplasm material, we performed a genome-wide association study of grain fissure resistance (GFR), the phenotype most associated with HRY, and found that the granule-bound starch synthase I gene Waxy is an important gene controlling GFR. Analysis of near-isogenic lines demonstrated that genetic variations in Waxy conferred different levels of tolerance to fissuring in grains. The null allele wx resulted in the highest GFR, while alleles that increased amylose synthesis reduced GFR. Increases in amylose content led to increases in the ratio of the widths of the amorphous layer to the semi-crystalline layer of the starch granules, and also to increased occurrence of chalkiness. The layer structure determined GFR by affecting the degree of swelling of granules in response to moisture, and chalkiness acted as an accelerator of moisture infiltration to rapidly increase the number of swelling granules. Our study reveals the molecular basis of GFR and HRY, thus opening the door for further understanding of the molecular networks of GFR and HRY.
整精米率是一个重要的品质性状，对灌浆期、收获期和收获后阶段的环境胁迫敏感。因此，选择具有优良整精米率性状的品种对于水稻生产和全球粮食安全非常重要；然而，该性状的分子基础尚不清楚。本研究利用丰富的水稻种质资源，对与整精米率关联最密切的稻谷裂颖抗性（GFR）进行了全基因组关联研究，发现粒状结合型淀粉合成酶 I 基因 Waxy 是控制 GFR 的重要基因。近等基因系分析表明，Waxy 基因的遗传变异赋予了籽粒不同程度的抗裂能力。wx 等位基因导致最高的 GFR，而增加直链淀粉合成的等位基因则降低了 GFR。直链淀粉含量的增加导致淀粉颗粒无定形层与半结晶层宽度之比增加，同时也增加了垩白的发生。层状结构通过影响颗粒在水分作用下的膨胀程度来决定 GFR，而垩白则作为水分渗透的加速剂，迅速增加膨胀颗粒的数量。本研究揭示了 GFR 和整精米率的分子基础，从而为进一步了解 GFR 和整精米率的分子网络打开了大门。
