Cellulose Synthase-Like D (CSLD) proteins, important for tip growth and cell division, are known to generate β-1,4-glucan. However, whether they are propelled in the membrane as the glucan chains they produce assemble into microfibrils is unknown. To address this, we endogenously tagged all eight CSLDs in Physcomitrium patens and discovered that they all localize to the apex of tip-growing cells and to the cell plate during cytokinesis. Actin is required to target CSLD to cell tips concomitant with cell expansion, but not to cell plates, which depend on actin and CSLD for structural support. Like Cellulose Synthase (CESA), CSLD requires catalytic activity to move in the plasma membrane. We discovered that CSLD moves significantly faster, with shorter duration and less linear trajectories than CESA. In contrast to CESA, CSLD movement was insensitive to the cellulose synthesis inhibitor isoxaben, suggesting that CSLD and CESA function within different complexes possibly producing structurally distinct cellulose microfibrils.

中文翻译：

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质膜中类似纤维素合酶的 D 运动需要酶活性

类纤维素合酶 D (CSLD) 蛋白对于尖端生长和细胞分裂很重要，已知可生成 β-1,4-葡聚糖。然而，当它们产生的葡聚糖链组装成微纤维时，它们是否在膜中被推进尚不清楚。为了解决这个问题，我们对小立碗藓中的所有八个 CSLD 进行内源标记，发现它们在胞质分裂过程中都定位于尖端生长细胞的顶端和细胞板。肌动蛋白需要将 CSLD 靶向细胞尖端并伴随细胞扩增，但不靶向细胞板，细胞板依赖肌动蛋白和 CSLD 提供结构支持。与纤维素合酶 (CESA) 一样，CSLD 需要催化活性才能在质膜中移动。我们发现，与 CESA 相比，CSLD 的移动速度明显更快，持续时间更短，线性轨迹更少。与CESA相比，CSLD运动对纤维素合成抑制剂异恶苯不敏感，这表明CSLD和CESA在不同的复合物中发挥作用，可能产生结构不同的纤维素微纤维。