Trimming of N-Glycans by the Golgi-Localized α-1,2-Mannosidases, MNS1 and MNS2, Is Crucial for Maintaining RSW2 Protein Abundance during Salt Stress in Arabidopsis

天门冬素(Asn/N ) 连接了 glycans 为蛋白质合拢， trafficking，和 endoplasmic 是重要的在优核质的联系蜂窝胃的降级。glycoproteins 的成熟包含在 Golgi 由另外的糖分子的 mannosidases 和三分支的 N-glycans 的增加整修 mannosyl 残余。然而，调停 Golgi 的甘露糖整修的生物重要性充分没被理解。这里，我们显示出二机能上地冗余的 mannosidases， MNS1 和 MNS2 的那废除，为在 A 和工厂 N-glycans 的 C 分支上整修的 -1,2-mannose 负责在 Arabidopsis 在盐压力条件下面导致严重的根生长抑制。相反，有在 oligosaccharide 先锋的生合成的缺点的异种当甘露糖整修不在时显示了提高的盐忍耐。然而，在 EBS3 的变化，为分叉的 N-glycan 先锋的形成被要求，压制了 mns1 mns2 的盐敏感的显型两倍异种。有趣地，我们观察了那 ? 纤维素生合成在高咸度下面在 mns1 mns2 根被损害。一致地， ? 许多膜抛锚了 endo -- 在纤维素生合成起一个关键作用的 1,4-endoglucanase (RSW2/KOR ) 和它的变异的变体 rsw2-1 ? 被调制由 ? 在盐应力下面整修的 -1,2-mannose。RSW2 的 Overexpression 能部分救 mns1 mns2 的盐敏感的显型。一起拿，这些结果建议 N-glycans 整修的那 MNS1/2-mediated 甘露糖在 modulating glycoprotein 丰富是关键的在植物承受盐应力。

Asparagine （Asn/N）-Iinked glycans are important for protein folding, trafficking, and endoplasmic reticulum-associated degradation in eukaryotes. The maturation of glycoproteins involves the trimming of mannosyl residues by mannosidases and addition of other sugar molecules to three-branched N-glycans in the Golgi. However, the biological importance of Golgi-mediated mannose trimming is not fully understood. Here, we show that abolishment of two functionally redundant mannosidases, MNS1 and MNS2, responsible for α-1,2-mannose trimming on the A and C branches of plant N-glycans lead to severe root growth inhibition under salt stress conditions in Arabidopsis. In contrast, mutants with defects in the biosynthesis of the oligosaccharide precursor displayed enhanced salt tolerance in the absence of mannose trimming. However, mutation in EBS3, which is required for the formation of the branched N-glycan precursor, suppressed the salt-sensitive phenotype of mnsl mns2 double mutant. Interestingly, we observed that cellulose biosynthesis was compromised in mnsl mns2 roots under high salinity. Consistently, abundance of a membrane anchored endo-13-1,4-endoglucanase （RSW2/KOR） that plays a key role in cellulose biosynthesis and its mutant variant rsw2-1 were modulated by α-1,2-mannose trimming under salt stress. Overexpression of RSW2 could partially rescue the salt-sensitive phenotype of mnsl mns2. Taken together, these results suggest that MNS1/2-mediated mannose trimming of N-glycans is crucial in modulating glycoprotein abundance to withstand salt stress in plants.