Transverse cortical microtubule orientation, critical for anisotropic cell expansion, is established in the meristematic root zone. Intending to elucidate the possible prerequisites for this establishment and factors that are involved, microtubule organization was studied in roots of Arabidopsis thaliana, wild-type and the p60-katanin mutants fra2, ktn1-2 and lue1. Transverse cortical microtubule orientation in the meristematic root zone has proven to persist under several regimes inhibiting root elongation. This persistence was attributed to the constant moderate elongation of meristematic cells, prior to mitotic division. Therefore, A. thaliana wild-type seedlings were treated with aphidicolin, in order to prevent mitosis and inhibit premitotic cell elongation. In roots treated with aphidicolin for 12 h, cell divisions still occurred and microtubules were transverse. After 24 and 48 h of treatment, meristematic cell divisions and the prerequisite elongation ceased, while microtubule orientation became random. In meristematic cells of the p60-katanin mutants, apart from a general transverse microtubule pattern, cortical microtubules with random orientation were observed, also converging at several cortical sites, in contrast to the uniform transverse pattern of wild-type cells. Taken together, these observations reveal that transverse cortical microtubule orientation in the meristematic zone of A. thaliana root is cell division-dependent and requires severing by katanin.

中文翻译：

---

拟南芥根分生组织区的皮质微管取向取决于细胞分裂，需要通过katanin切断

在分生组织根部区域建立了对各向异性细胞扩展至关重要的横向皮层微管取向。为了阐明这种建立的可能前提和涉及的因素，在拟南芥，野生型和p60-katanin突变体fra2，ktn1-2和lue1的根中研究了微管组织。已证实在分生根区的横向皮层微管取向在几种抑制根伸长的机制下仍然存在。这种持久性归因于有丝分裂分裂之前分生细胞的持续适度伸长。因此，为了防止有丝分裂和抑制有丝分裂细胞的伸长，用蚜虫碱处理了拟南芥野生型幼苗。在用蚜虫碱处理12小时的根中，细胞分裂仍在发生，微管是横向的。治疗24和48小时后，分生细胞分裂和必要的伸长停止，而微管定向变得随机。在p60-katanin突变体的分生细胞中，除了一般的横向微管模式以外，还观察到了具有随机方向的皮质微管，并且与野生型细胞的均匀横向模式相反，它们也在几个皮质位点会聚。综上所述，这些观察结果表明，拟南芥根分生组织区中的横向皮质微管取向是细胞分裂依赖性的，并且需要被katanin切断。在p60-katanin突变体的分生细胞中，除了一般的横向微管模式以外，还观察到了具有随机方向的皮质微管，并且与野生型细胞的均匀横向模式相反，它们也在几个皮质位点会聚。综上所述，这些观察结果表明，拟南芥根分生组织区中的横向皮质微管取向是细胞分裂依赖性的，并且需要被katanin切断。在p60-katanin突变体的分生细胞中，除了一般的横向微管模式以外，还观察到了具有随机方向的皮质微管，并且与野生型细胞的均匀横向模式相反，它们也在几个皮质位点会聚。综上所述，这些观察结果揭示了拟南芥根分生组织区中的横向皮质微管取向是细胞分裂依赖性的，并且需要被katanin切断。