Interaction between autonomous and microtubule guidance systems controls cellulose synthase trajectories Item

<b>The organisation 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 organisation by guiding cellulose synthase complexes</b><b>. However, cellulose synthase trajectories can be maintained when microtubules are removed by drugs, suggesting a separate guidance mechanism is also at play</b><b>. 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. </b>

纤维素微纤丝（cellulose microfibrils）的组织排布对植物细胞壁的机械强度与生长发育至关重要。已有研究证实，微管（microtubules）可通过引导纤维素合酶复合物（cellulose synthase complexes）的定位，在调控微纤丝的组织方式中发挥核心作用。然而，当通过药物移除微管后，纤维素合酶的运动轨迹仍可得以维持，这提示还存在另一套独立的引导机制。本研究通过抑制微管的动态变化，揭示了这套全新的调控机制：我们发现纤维素合酶复合物可与其他复合物遗留的运动轨迹发生相互作用，使其沿原有轨迹行进或最终消失。这些轨迹的稳定性，以及其方向对纤维素酶处理的敏感性，表明它们极有可能对应新生的纤维素微纤丝。仅依靠这套自主调控机制，即可在数小时内改变纤维素合酶运动轨迹的主导取向。但该机制的调控效果可被微管引导系统所覆盖。我们的研究结果支持双重引导模型：即存在一套依赖于纤维素合酶与微纤丝相互作用的自主系统，可维持纤维素合酶轨迹的排布对齐；而微管引导系统则可通过环境与发育信号，对纤维素合酶的排布取向进行精准调控。