Division of Applied Life Science (BK21 Program) and PMBBRC, Gyeongsang National University, 501 Jinju-daero, Jinju, 660-701, Korea.
Plant J. 2013 Mar;73(6):966-79. doi: 10.1111/tpj.12087. Epub 2013 Feb 25.
To explore the physiological significance of N-glycan maturation in the plant Golgi apparatus, gnt1, a mutant with loss of N-acetylglucosaminyltransferase I (GnTI) function, was isolated in Oryza sativa. gnt1 exhibited complete inhibition of N-glycan maturation and accumulated high-mannose N-glycans. Phenotypic analyses revealed that gnt1 shows defective post-seedling development and incomplete cell wall biosynthesis, leading to symptoms such as failure in tiller formation, brittle leaves, reduced cell wall thickness, and decreased cellulose content. The developmental defects of gnt1 ultimately resulted in early lethality without transition to the reproductive stage. However, callus induced from gnt1 seeds could be maintained for periods, although it exhibited a low proliferation rate, small size, and hypersensitivity to salt stress. Shoot regeneration and dark-induced leaf senescence assays indicated that the loss of GnTI function results in reduced sensitivity to cytokinin in rice. Reduced expression of A-type O. sativa response regulators that are rapidly induced by cytokinins in gnt1 confirmed that cytokinin signaling is impaired in the mutant. These results strongly support the proposed involvement of N-glycan maturation in transport as well as in the function of membrane proteins that are synthesized via the endomembrane system.
为了探索植物高尔基体中 N-聚糖成熟的生理意义，我们在水稻中分离了一个丧失 N-乙酰葡萄糖胺基转移酶 I（GnTI）功能的 gnt1 突变体。gnt1 表现出 N-聚糖成熟的完全抑制作用，并积累了高甘露糖 N-聚糖。表型分析表明，gnt1 表现出幼苗发育缺陷和不完全的细胞壁生物合成，导致分蘖形成失败、叶片脆弱、细胞壁厚度降低和纤维素含量减少等症状。gnt1 的发育缺陷最终导致早期死亡，而无法进入生殖阶段。然而，来自 gnt1 种子的愈伤组织可以被维持一段时间，尽管它表现出低增殖率、小尺寸和对盐胁迫的高敏感性。芽再生和暗诱导叶片衰老试验表明，GnTI 功能的丧失导致水稻中细胞分裂素敏感性降低。gnt1 中细胞分裂素快速诱导的 A 型水稻响应调节剂的表达减少证实了突变体中细胞分裂素信号受损。这些结果强烈支持了 N-聚糖成熟在运输以及通过内质网系统合成的膜蛋白功能中的参与。
