Cellulose Synthase Tethering Attenuates Mechano-induced Microtubule Organization in pavement cells

Mechanical forces control development in plants and animals, acting as cues in pattern formation and as the driving force of morphogenesis. In mammalian cells, molecular assemblies residing at the interface of the cell membrane and the extracellular matrix play an important role in perceiving and transmitting external mechanical signals to trigger physiological responses. Similar processes occur in plants, but there is little understanding of the molecular mechanisms and their genetic basis. Here, we show that number and movements directions of cellulose synthase complexes (CSCs) at the plasma membrane vary during initial stages of development in the cotyledon epidermis of Arabidopsis, closely mirroring the microtubule organization. Uncoupling microtubules and CSCs resulted in enhanced microtubule co-alignment as caused by mechanical stimuli driven either by cell shape or by tissue-scale physical perturbations. Furthermore, micromechanical perturbation resulted in depletion of CSCs from the plasma membrane suggesting a possible link between cellulose synthase removal from the plasma membrane and microtubule response to mechanical stimuli. Taken together, our results suggest that the interaction of cellulose synthase and cortical microtubules forms a physical continuum between the cell wall, plasma membrane, and the cytoskeleton that modulates the mechano-response of the cytoskeleton.机械力在动植物发育过程中发挥调控作用，既可作为模式形成的诱导信号，也可作为形态发生的驱动力。在哺乳动物细胞中，定位于细胞膜与细胞外基质交界处的分子复合物，在感知并传递外界机械信号以触发生理响应的过程中发挥关键作用。植物中也存在类似过程，但目前对其分子机制及遗传基础的认知仍十分有限。本研究发现，拟南芥子叶表皮发育早期，质膜上的纤维素合酶复合物（cellulose synthase complexes, CSCs）的数量与运动方向会发生动态变化，且这一变化与微管组织模式高度吻合。将微管与CSCs解偶联后，由细胞形状或组织尺度物理扰动所引发的机械刺激，会导致微管的共对齐程度进一步增强。此外，微机械扰动会导致质膜上的CSCs发生耗竭，这表明质膜上纤维素合酶的移除与微管对机械刺激的响应之间可能存在关联。综上，本研究结果表明，纤维素合酶与皮层微管（cortical microtubules）的相互作用，在细胞壁、质膜与细胞骨架之间构建了物理连续体，进而调控细胞骨架的机械响应。