Department of Genetics and Cell Biology, College of Life Sciences, Nankai University, Tianjin, 300071, China.
Tianjin Key Laboratory of Crop Genetics and Breeding, Crop Research Institute, Tianjin Academy of Agricultural Sciences, Tianjin, 300384, China.
Plant Mol Biol. 2024 Aug 22;114(5):91. doi: 10.1007/s11103-024-01488-z.
Inositol 1,3,4,5,6-pentakisphosphate 2-kinase (IPK1) catalyzes the final step in phytic acid (InsP) synthesis. In this study, the effects of OsIPK1 mutations on InsP synthesis, grain filling and their underlying mechanisms were investigated. Seven gRNAs were designed to disrupt the OsIPK1 gene via CRISPR/CAS9 system. Only 4 of them generated 29 individual insertion or deletion T plants, in which nine biallelic or heterozygous genotypes were identified. Segregation analysis revealed that OsIPK1 frameshift mutants are homozygous lethality. The biallelic and heterozygous frameshift mutants exhibited significant reduction in yield-related traits, particularly in the seed-setting rate and yield per plant. Despite a notable decline in pollen viability, the male and female gametes had comparable transmission rates to their progenies in the mutants. A significant number of the filling-aborted (FA) grains was observed in mature grains of these heterozygous frameshift mutants. These grains exhibited a nearly complete blockage of InsP synthesis, resulting in a pronounced increase in Pi content. In contrast, a slight decline in InsP content was observed in the plump grains. During the filling stage, owing to the excessive accumulation of Pi, starch synthesis was significantly impaired, and the endosperm development-specific gene expression was nearly abolished. Consistently, the activity of whereas AGPase, a key enzyme in starch synthesis, was significantly decreased and Pi transporter gene expression was upregulated in the FA grains. Taken together, these results demonstrate that OsIPK1 frameshift mutations result in excessive Pi accumulation, decreased starch synthesis, and ultimately leading to lower yields in rice.
肌醇 1,3,4,5,6-五磷酸 2-激酶（IPK1）催化植酸（InsP）合成的最后一步。在这项研究中，研究了 OsIPK1 突变对 InsP 合成、灌浆和其潜在机制的影响。设计了 7 个 gRNA 通过 CRISPR/CAS9 系统破坏 OsIPK1 基因。只有 4 个产生了 29 个个体插入或缺失 T 植物，其中鉴定出 9 个双等位基因或杂合基因型。分离分析表明 OsIPK1 移码突变体是纯合致死的。双等位基因和杂合移码突变体表现出与产量相关性状的显著减少，特别是在结实率和单株产量上。尽管花粉活力明显下降，但突变体中的雄性和雌性配子与后代的传递率相当。在这些杂合移码突变体的成熟种子中观察到大量的灌浆中止（FA）粒。这些粒表现出 InsP 合成的几乎完全阻断，导致 Pi 含量显著增加。相比之下，饱满粒中的 InsP 含量略有下降。在灌浆阶段，由于 Pi 的过度积累，淀粉合成受到严重损害，胚乳发育特异性基因表达几乎被废除。一致地，AGPase 的活性，淀粉合成的关键酶，显著降低，Pi 转运蛋白基因表达在 FA 粒中上调。总之，这些结果表明 OsIPK1 移码突变导致 Pi 积累过多，淀粉合成减少，最终导致水稻产量降低。
