Plant interphase cortical microtubules (cMTs) mediate anisotropic cell expansion in response to environmental and developmental cues. In Arabidopsis thaliana, KATANIN 1 (KTN1), the p60 catalytic subunit of the conserved MT‐severing enzyme katanin, is essential for cMT ordering and anisotropic cell expansion. However, the regulation of KTN1‐mediated cMT severing and ordering remains unclear. In this work, we report that the Arabidopsis IQ67 DOMAIN (IQD) family gene ABNORMAL SHOOT 6 (ABS6) encodes a MT‐associated protein. Overexpression of ABS6 leads to elongated cotyledons, directional pavement cell expansion, and highly ordered transverse cMT arrays. Genetic suppressor analysis revealed that ABS6‐mediated cMT ordering is dependent on KTN1 and SHADE AVOIDANCE 4 (SAV4). Live imaging of cMT dynamics showed that both ABS6 and SAV4 function as positive regulators of cMT severing. Furthermore, ABS6 directly interacts with KTN1 and SAV4 and promotes their recruitment to the cMTs. Finally, analysis of loss‐of‐function mutant combinations showed that ABS6, SAV4, and KTN1 work together to ensure the robust ethylene response in the apical hook of dark‐grown seedlings. Together, our findings establish ABS6 and SAV4 as positive regulators of cMT severing and ordering, and highlight the role of cMT dynamics in fine‐tuning differential growth in plants.

中文翻译：

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ABNORMAL SHOOT 6 与 KATAN 1 和 SHADE AVOIDANCE 4 相互作用以促进拟南芥中的皮层微管切断和排序

植物间期皮质微管 (cMTs) 介导各向异性细胞扩张以响应环境和发育线索。在拟南芥中，KATANIN 1 (KTN1) 是保守的 MT 切断酶 katanin 的 p60 催化亚基，对于 cMT 排序和各向异性细胞扩增至关重要。然而，KTN1 介导的 cMT 切断和排序的调节仍不清楚。在这项工作中，我们报告了拟南芥IQ67 域 (IQD) 家族基因ABNORMAL SHOOT 6 ( ABS6 ) 编码一种 MT 相关蛋白。ABS6 的过度表达导致子叶拉长、定向路面细胞扩张和高度有序的横向 cMT 阵列。基因抑制分析显示 ABS6 介导的 cMT 排序依赖于 KTN1 和 SHADE AVOIDANCE 4 (SAV4)。cMT 动力学的实时成像显示 ABS6 和 SAV4 作为 cMT 切断的正调节因子。此外，ABS6 直接与 KTN1 和 SAV4 相互作用并促进它们向 cMT 的募集。最后，对功能缺失突变体组合的分析表明，ABS6、SAV4 和 KTN1 共同作用以确保深色生长幼苗顶端钩中的强劲乙烯反应。总之，我们的研究结果将 ABS6 和 SAV4 确立为 cMT 切断和排序的正调节因子，并突出了 cMT 动力学在微调植物差异生长中的作用。