Composition and structure of endosperm starch are major determinant factors for rice quality. Glycosylinositol phosphorylceramides (GIPC) is a kind of sphingolipid and it accounts for ~ 25% of total plasma membrane lipids in plants. The relationship between synthesis of GIPC and development of endosperm starch, however, remains unclear. We here identified a mutant with a floury and opaque endosperm, named floury and shrunken endosperm 6 (fse6). The mutant seeds displayed a shrunken grain appearance. Physicochemical analysis showed that both total starch and amylose contents were decreased, while lipid and protein contents were increased in the mature mutant seeds, compared to their counterparts in the wild type. Further observation of semi-thin sections indicated the development of mutant amyloplasts was defective. The mutant seeds germinated normally but failed to survive in a later stage of seedling growth. Map-based cloning and genetic complementation revealed that FSE6 encodes a glycosyltransferase and is homologous to Arabidopsis GLUCOSAMINE INOSITOLPHOSPHORYLCERAMIDE TRANSFERASE1 (GINT1), an enzyme vital for GIPC synthesis. We further found that cellulose content and starch biosynthesis in the mutant were altered. This study connects a gap between a rice GINT1 and starch synthesis, which will be helpful for rice quality improvement.

胚乳淀粉的组成和结构是影响稻米品质的主要决定因素。糖基肌醇磷酸神经酰胺（GIPC）是一种鞘脂，占植物总质膜脂质的〜25％。GIPC的合成与胚乳淀粉的发育之间的关系仍然不清楚。我们在这里鉴定出一个具有面粉状和不透明胚乳的突变体，名为面粉状和萎缩的胚乳6（fse6）。突变种子显示出收缩的谷物外观。理化分析表明，与野生型相比，成熟突变体种子的总淀粉和直链淀粉含量均降低，脂质和蛋白质含量均升高。半薄切片的进一步观察表明突变体淀粉体的发育是有缺陷的。突变种子正常发芽，但在幼苗生长的后期无法存活。基于图的克隆和遗传互补揭示了FSE6编码一个糖基转移酶，与拟南芥葡糖胺肌苷磷脂酰转移酶1（GINT1）同源，后者对GIPC合成至关重要。我们进一步发现该突变体中的纤维素含量和淀粉生物合成被改变。这项研究将水稻GINT1与淀粉合成之间的差距联系起来，这将有助于提高水稻的品质。