For the unicellular alga Chlamydomonas reinhardtii, the presence of N-glycosylated proteins on the surface of two flagella is crucial for both cell-cell interaction during mating and flagellar surface adhesion. However, it is not known whether only the presence or also the composition of N-glycans attached to respective proteins is important for these processes. To this end, we tested several C. reinhardtii insertional mutants and a CRISPR/Cas9 knockout mutant of xylosyltransferase 1A, all possessing altered N-glycan compositions. Taking advantage of atomic force microscopy and micropipette force measurements, our data revealed that reduction in N-glycan complexity impedes the adhesion force required for binding the flagella to surfaces. This results in impaired polystyrene bead binding and transport but not gliding of cells on solid surfaces. Notably, assembly, intraflagellar transport, and protein import into flagella are not affected by altered N-glycosylation. Thus, we conclude that proper N-glycosylation of flagellar proteins is crucial for adhering C. reinhardtii cells onto surfaces, indicating that N-glycans mediate surface adhesion via direct surface contact.

中文翻译：

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改变的 N-聚糖组成影响莱茵衣藻鞭毛介导的粘附

对于单细胞藻类莱茵衣藻，两个鞭毛表面 N-糖基化蛋白的存在对于交配和鞭毛表面粘附过程中的细胞间相互作用至关重要。然而，尚不知道是否只有连接到相应蛋白质上的 N-聚糖的存在或组成对这些过程很重要。为此，我们测试了几个莱茵衣藻插入突变体和木糖基转移酶 1A 的 CRISPR/Cas9 敲除突变体，它们都具有改变的 N-聚糖组成。利用原子力显微镜和微量移液管力测量，我们的数据显示 N-聚糖复杂性的降低阻碍了将鞭毛结合到表面所需的粘附力。这会导致聚苯乙烯珠结合和运输受损，但不会导致细胞在固体表面上滑动。值得注意的是，组装、鞭毛内运输和蛋白质进入鞭毛不受 N-糖基化改变的影响。因此，我们得出结论，鞭毛蛋白的适当 N-糖基化对于将莱茵衣藻细胞粘附到表面上至关重要，这表明 N-聚糖通过直接表面接触介导表面粘附。