Department of Cell and Developmental Biology, John Innes Centre, Colney Lane, Norwich NR4 7UH, UK.
Curr Biol. 2020 Mar 9;30(5):941-947.e2. doi: 10.1016/j.cub.2019.12.066. Epub 2020 Feb 6.
The organization of cellulose microfibrils is critical for the strength and growth of plant cell walls. Microtubules have been shown to play a key role in controlling microfibril organization by guiding cellulose synthase complexes [1-4]. However, cellulose synthase trajectories can be maintained when microtubules are removed by drugs, suggesting a separate guidance mechanism is also at play [1, 5, 6]. By slowing down microtubule dynamics, we reveal such a mechanism by showing that cellulose synthase complexes can interact with the trails left by other complexes, causing them to follow the trails or disappear. The stability of the trails, together with the sensitivity of their directions to cellulase treatment, indicates they most likely reflect nascent cellulose microfibrils. Over many hours, this autonomous mechanism alone can lead to a change in the dominant orientation of cellulose synthase trajectories. However, the mechanism can be overridden by the microtubule guidance system. Our findings suggest a dual guidance model, in which an autonomous system, involving interaction between cellulose synthases and microfibrils, can maintain aligned cellulose synthase trajectories, while a microtubule guidance system allows alignments to be steered by environmental and developmental cues.
纤维素微纤维的组织对于植物细胞壁的强度和生长至关重要。微管已被证明通过引导纤维素合酶复合物在控制微纤维组织方面发挥关键作用[1-4]。然而，当微管被药物去除时，纤维素合酶轨迹可以被维持，这表明还有一个单独的导向机制在起作用[1, 5, 6]。通过减缓微管动力学，我们通过显示纤维素合酶复合物可以与其他复合物留下的轨迹相互作用，从而使它们沿着轨迹或消失，揭示了这样一个机制。轨迹的稳定性，以及它们方向对纤维素酶处理的敏感性，表明它们很可能反映了新形成的纤维素微纤维。在多个小时内，这种自主机制本身就可以导致纤维素合酶轨迹的主导方向发生变化。然而，该机制可以被微管导向系统所覆盖。我们的发现表明存在一个双重导向模型，其中一个自主系统，涉及纤维素合酶和微纤维之间的相互作用，可以维持对齐的纤维素合酶轨迹，而微管导向系统允许通过环境和发育线索来引导对齐。
