Evidence is accumulating implicating cortical microtubules in the directional control of cell expansion. However, the role of actin filaments in this process is still uncertain. To determine the involvement of actin in cell elongation, the organization of actin filaments in primary roots of maize (Zea mays L.) was examined by use of an improved fluorochrome-conjugated phalloidin-labeling method. With this method, a previously undetected state of actin organization was revealed in the elongation and maturation zone of maize roots. Fine transversely oriented cortical actin was observed in all cells of the elongation zone, including the epidermis, cortex, and vascular tissues. The orientation of cortical actin shifted from a predominantly transverse orientation to oblique, longitudinal, and/or random arrangements as the cells matured. The reorientation of cortical actin in maturing root cells mimics the behavior of cortical microtubules reported in other studies. Furthermore, roots treated with the microtubule-stabilizing drug taxol improved the quality of actin preservation as evidenced by the thicker bundles of cortical actin. This suggested that taxol was also capable of stabilizing the cortical actin networks. The elongation of roots exposed to 1 micromole Latrunculin B, an actin-disrupting drug, was inhibited, and after 24 h the roots exhibited moderate swelling particularly along the elongation zone. Latrunculin B also caused microtubules to reorient from transverse to oblique arrays. The results from this study provide evidence that cortical microtubules and actin filaments respond in a coordinated way to environmental signals and may well depend on both elements of the cytoskeleton.

中文翻译：

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皮层肌动蛋白丝可能与皮层微管相互作用，调节玉米初生根细胞扩张的极性（Zea mays L.）

越来越多的证据表明皮层微管参与细胞扩张的定向控制。然而，肌动蛋白丝在这一过程中的作用仍不确定。为了确定肌动蛋白在细胞伸长中的作用，通过使用改进的荧光染料偶联鬼笔环肽标记方法检查了玉米 (Zea mays L.) 初生根中肌动蛋白丝的组织。使用这种方法，在玉米根的伸长和成熟区揭示了以前未检测到的肌动蛋白组织状态。在伸长区的所有细胞，包括表皮、皮质和血管组织中都观察到精细的横向定向的皮质肌动蛋白。随着细胞的成熟，皮质肌动蛋白的方向从主要的横向方向转变为倾斜、纵向和/或随机排列。成熟根细胞中皮质肌动蛋白的重新定向模拟了其他研究中报道的皮质微管的行为。此外，用较厚的皮质肌动蛋白束证明，用微管稳定药物紫杉醇处理的根改善了肌动蛋白保存的质量。这表明紫杉醇也能够稳定皮质肌动蛋白网络。暴露于 1 微摩尔 Latrunculin B（一种肌动蛋白破坏药物）的根的伸长受到抑制，24 小时后根表现出中度肿胀，特别是沿着伸长区。Latrunculin B 还导致微管从横向阵列重新定向为斜阵列。