PDF(Pubmed)
Abstract：
Although the formation of new walls during plant cell division tends to follow maximal tensile stress direction, analyses of individual cells over time reveal a much more variable behavior. The origin of such variability as well as the exact role of interphasic microtubule behavior before cell division have remained mysterious so far. To approach this question, we took advantage of the Arabidopsis stem, where the tensile stress pattern is both highly anisotropic and stable. Although cortical microtubules (CMTs) generally align with maximal tensile stress, we detected a specific time window, ca. 3 h before cell division, where cells form a radial pattern of CMTs. This microtubule array organization preceded preprophase band (PPB) formation, a transient CMT array predicting the position of the future division plane. It was observed under different growth conditions and was not related to cell geometry or polar auxin transport. Interestingly, this cortical radial pattern correlated with the well-documented increase of cytoplasmic microtubule accumulation before cell division. This radial organization was prolonged in cells of the trm678 mutant, where CMTs are unable to form a PPB. Whereas division plane orientation in trm678 is noisier, we found that cell division symmetry was in contrast less variable between daughter cells. We propose that this \"radial step\" reflects a trade-off in robustness for two essential cell division attributes: symmetry and orientation. This involves a \"reset\" stage in G2, where an increased cytoplasmic microtubule accumulation transiently disrupts CMT alignment with tissue stress.
摘要：
尽管在植物细胞分裂过程中新壁的形成倾向于遵循最大拉伸应力方向，随着时间的推移，对单个细胞的分析揭示了一种更加多变的行为。迄今为止，这种变异性的起源以及细胞分裂前相间微管行为的确切作用仍然是神秘的。为了解决这个问题，我们利用了拟南芥的茎,其中拉伸应力模式是高度各向异性和稳定的。尽管皮质微管（CMT）通常与最大拉伸应力对齐，我们检测到一个特定的时间窗口，CA.细胞分裂前3小时，其中细胞形成CMT的放射状模式。这种微管阵列组织先于前期带(PPB)形成，预测未来分割平面位置的瞬态CMT阵列。在不同的生长条件下观察到，与细胞几何形状或极性生长素转运无关。有趣的是,这种皮质放射状模式与有据可查的细胞分裂前细胞质微管积累的增加相关.这种放射状组织在trm678突变体的细胞中延长，其中CMT无法形成PPB。而trm678中的划分平面方向更嘈杂，我们发现细胞分裂对称性在子细胞之间的差异较小。我们建议此“径向步长”反映了两个基本细胞分裂属性的鲁棒性权衡：对称性和方向性。这涉及G2中的“重置”阶段，其中细胞质微管积累的增加会暂时破坏CMT与组织应激的对齐。
