Cortical microtubules regulate cell expansion by determining cellulose microfibril orientation in the root apex of Arabidopsis thaliana. While the regulation of cell wall properties by cortical microtubules is well studied, the data on the influence of cell wall to cortical microtubule organization and stability remain scarce. Studies on cellulose biosynthesis mutants revealed that cortical microtubules depend on Cellulose Synthase A (CESA) function and/or cell expansion. Furthermore, it has been reported that cortical microtubules in cellulose-deficient mutants are hypersensitive to oryzalin. In this work, the persistence of cortical microtubules against anti-microtubule treatment was thoroughly studied in the roots of several cesa mutants, namely thanatos, mre1, any1, prc1-1 and rsw1, and the Cellulose Synthase Interacting 1 protein (csi1) mutant pom2-4. In addition, various treatments with drugs affecting cell expansion were performed on wild-type roots. Whole mount tubulin immunolabeling was applied in the above roots and observations were performed by confocal microscopy. Cortical microtubules in all mutants showed statistically significant increased persistence against anti-microtubule drugs, compared to those of the wild-type. Furthermore, to examine if the enhanced stability of cortical microtubules was due to reduced cellulose biosynthesis or to suppression of cell expansion, treatments of wild-type roots with 2,6-dichlorobenzonitrile (DCB) and Congo red were performed. After these treatments, cortical microtubules appeared more resistant to oryzalin, than in the control. According to these findings, it may be concluded that inhibition of cell expansion, irrespective of the cause, results in increased microtubule stability in A. thaliana root. In addition, cell expansion does not only rely on cortical microtubule orientation but also plays a regulatory role in microtubule dynamics, as well. Various hypotheses may explain the increased cortical microtubule stability under decreased cell expansion such as the role of cell wall sensors and the presence of less dynamic cortical microtubules.

中文翻译：

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抑制细胞扩张可增强拟南芥根尖皮层微管的稳定性

皮质微管通过确定拟南芥根尖中的纤维素微纤维方向来调节细胞扩张。虽然皮质微管对细胞壁特性的调节得到了很好的研究，但关于细胞壁对皮质微管组织和稳定性的影响的数据仍然很少。对纤维素生物合成突变体的研究表明，皮质微管依赖于纤维素合成酶 A (CESA) 的功能和/或细胞扩增。此外，据报道，纤维素缺乏突变体中的皮质微管对 oryzalin 过敏。在这项工作中，在几个 cesa 突变体的根中彻底研究了皮质微管对抗微管处理的持久性，即thanatos、mre1、any1、prc1-1 和 rsw1，和纤维素合酶相互作用 1 蛋白 (csi1) 突变体 pom2-4。此外，对野生型根进行了各种影响细胞扩增的药物处理。在上述根中应用整体微管蛋白免疫标记，并通过共聚焦显微镜进行观察。与野生型相比，所有突变体中的皮质微管对抗微管药物的持久性在统计学上显着增加。此外，为了检查皮质微管稳定性的增强是否是由于纤维素生物合成减少或细胞扩张受到抑制，用 2,6-二氯苄腈 (DCB) 和刚果红处理野生型根。在这些处理之后，与对照相比，皮质微管似乎对安磺灵更具抗性。根据这些发现，可以得出结论，不管原因如何，抑制细胞扩张都会导致拟南芥根中微管稳定性的增加。此外，细胞扩增不仅依赖于皮质微管方向，而且在微管动力学中也起着调节作用。各种假设可以解释在细胞扩张减少的情况下皮层微管稳定性的增加，例如细胞壁传感器的作用和动态皮层微管的存在。