Glycosylphosphatidylinositol (GPI) anchoring is a common protein modification that targets proteins to the plasma membrane (PM). Knowledge about the GPI lipid tail, which guides the secretion of GPI-anchored proteins (GPI-APs), is limited in plants. Here, we report that rice (Oryza sativa) BRITTLE CULM16 (BC16), a membrane-bound O-acyltransferase (MBOAT) remodels GPI lipid tails and governs cell wall biomechanics. The bc16 mutant exhibits fragile internodes, resulting from reduced cell wall thickness and cellulose content. BC16 is the only MBOAT in rice and is located in the endoplasmic reticulum and Golgi apparatus. Yeast gup1Δ mutant restoring assay and GPI lipid composition analysis demonstrated BC16 as a GPI lipid remodelase. Loss of BC16 alters GPI lipid structure and disturbs the targeting of BC1, a GPI-AP for cellulose biosynthesis, to the PM lipid nanodomains. Atomic force microscopy revealed compromised deposition of cellulosic nanofibers in bc16, leading to an increased Young's modulus and abnormal mechanical properties. Therefore, BC16-mediated lipid remodeling directs the GPI-APs, such as BC1, to the cell surface to fulfill multiple functions, including cellulose organization. Our work unravels a mechanism by which GPI lipids are remodeled in plants and provides insights into the control of cell wall biomechanics, offering a tool for breeding elite crops with improved support strength.

中文翻译：

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糖基磷脂酰肌醇锚定脂质重塑将蛋白质引导至质膜并控制细胞壁力学。

糖基磷脂酰肌醇 (GPI) 锚定是一种常见的蛋白质修饰，可将蛋白质靶向质膜 (PM)。在植物中，关于引导 GPI 锚定蛋白 (GPI-AP) 分泌的 GPI 脂质尾部的知识有限。在这里，我们报道了水稻 (Oryza sativa) BRITTLE CULM16 (BC16)，一种膜结合 O-酰基转移酶 (MBOAT) 重塑 GPI 脂质尾部并控制细胞壁生物力学。bc16 突变体由于细胞壁厚度和纤维素含量减少而表现出脆弱的节间。BC16是水稻中唯一的MBOAT，位于内质网和高尔基体中。酵母 gup1Δ 突变体恢复测定和 GPI 脂质成分分析证明 BC16 是一种 GPI 脂质重塑酶。BC16 的缺失会改变 GPI 脂质结构，并干扰 BC1（一种用于纤维素生物合成的 GPI-AP）对 PM 脂质纳米结构域的靶向。原子力显微镜显示 bc16 中纤维素纳米纤维的沉积受损，导致杨氏模量增加和机械性能异常。因此，BC16 介导的脂质重塑将 GPI-AP（例如 BC1）引导至细胞表面以实现多种功能，包括纤维素组织。我们的工作揭示了 GPI 脂质在植物中重塑的机制，并提供了对细胞壁生物力学控制的见解，为培育具有更高支持强度的优良作物提供了工具。