n nnnIn eukaryotes, class I -mannosidases are involved in early N-glycanprocessing reactions and in N-glycan–dependent qualitycontrol in the endoplasmic reticulum (ER). To investigate therole of these enzymes in plants, we identified the ER-type -mannosidaseI (MNS3) and the two Golgi--mannosidase I proteins (MNS1 andMNS2) from Arabidopsis thaliana. All three MNS proteins werefound to localize in punctate mobile structures reminiscentof Golgi bodies. Recombinant forms of the MNS proteins wereable to process oligomannosidic N-glycans. While MNS3 efficientlycleaved off one selected 1,2-mannose residue from Man9GlcNAc2,MNS1/2 readily removed three 1,2-mannose residues from Man8GlcNAc2.Mutation in the MNS genes resulted in the formation of aberrantN-glycans in the mns3 single mutant and Man8GlcNAc2 accumulationin the mns1 mns2 double mutant. N-glycan analysis in the mnstriple mutant revealed the almost exclusive presence of Man9GlcNAc2,demonstrating that these three MNS proteins play a key rolein N-glycan processing. The mns triple mutants displayed short,radially swollen roots and altered cell walls. Pharmacologicalinhibition of class I -mannosidases in wild-type seedlings resultedin a similar root phenotype. These findings show that classI -mannosidases are essential for early N-glycan processingand play a role in root development and cell wall biosynthesisin Arabidopsis.展开▼
机译:ABSTRACTn FONT> TH> TR> TABLE> n
n TOP n <字体颜色= 464c53>抽象 FONT> n 结果 n 讨论 n 方法 n 参考资料 n FONT> TH> TR> TABLE > n nnn在真核生物中,I类-甘露糖苷酶与早期N-聚糖 SUP有关>加工反应和N-聚糖依赖性质量 S UP>内质网(ER)中的控制。为了研究植物中这些酶的 SUP>作用,我们鉴定了ER型-甘露糖苷酶 SUP> I(MNS3)和两个高尔基体--甘露糖苷酶I蛋白(MNS1和 SUP> MNS2),来自 Arabidopsis thaliana I>。发现这三种MNS蛋白都位于 SUP>的点状移动结构中,使人联想到高尔基体的 SUP>。 MNS蛋白的重组形式可以处理低聚甘露糖苷N-聚糖。尽管MNS3有效地 SUP>从Man 切下一个选定的 1,2-甘露糖残基9 SUB> GlcNAc 2 SUB>, SUP> MNS1 / 2轻松删除了三个 8 SUB> GlcNAc 2 SUB>中的0“> 1,2-甘露糖残基。 MNS I>基因中的 SUP>突变导致 mns3 I>单个突变体和Man 8 SUB> GlcNAc 2 SUB>积累中的 SUP> N聚糖异常形成 < / SUP>在 mns1 mns2 I>双重突变体中。在 mns I> SUP>三重突变体中进行的N-聚糖分析表明,Man 9 SUB> GlcNAc 2 SUB>, SUP>证明这三种MNS蛋白在N-聚糖加工中起着关键作用 SUP>。 mns I>三重突变体显示出短的, SUP>径向根肿胀和细胞壁改变。 I类-甘露糖苷酶在野生型幼苗中的药理抑制作用 SUP> SUP>具有相似的根表型。这些发现表明,类 SUP> I -甘露糖苷酶对于早期N-聚糖加工至关重要。 > SUP>,并在拟南芥 I>的根发育和细胞壁生物合成中起作用。 SUP>
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