TCS1, a Microtubule-Binding Protein, Interacts with KCBP/ZWICHEL to Regulate Trichome Cell Shape in Arabidopsis thaliana

How cell shape is controlled is a fundamental question in developmental biology, but the genetic and molecular mechanisms that determine cell shape are largely unknown. Arabidopsis trichomes have been used as a good model system to investigate cell shape at the single-cell level. Here we describe the trichome cell shape 1 (tcs1) mutants with the reduced trichome branch number in Arabidopsis. TCS1 encodes a coiled-coil domain-containing protein. Pharmacological analyses and observations of microtubule dynamics show that TCS1 influences the stability of microtubules. Biochemical analyses and live-cell imaging indicate that TCS1 binds to microtubules and promotes the assembly of microtubules. Further results reveal that TCS1 physically associates with KCBP/ZWICHEL, a microtubule motor involved in the regulation of trichome branch number. Genetic analyses indicate that kcbp/zwi is epistatic to tcs1 with respect to trichome branch number. Thus, our findings define a novel genetic and molecular mechanism by which TCS1 interacts with KCBP to regulate trichome cell shape by influencing the stability of microtubules.

细胞形态的调控机制是发育生物学领域的核心科学问题，但决定细胞形态的遗传与分子机制迄今仍未被充分阐明。拟南芥（Arabidopsis）表皮毛（trichomes）已被广泛用作单细胞水平研究细胞形态调控的优质模型体系。本研究报道了拟南芥中表皮毛分支数减少的trichome cell shape 1（tcs1）突变体。TCS1编码一种含有卷曲螺旋结构域的蛋白（coiled-coil domain-containing protein）。药理学分析与微管动力学观测结果表明，TCS1可影响微管稳定性。生化分析与活细胞成像（live-cell imaging）实验证实，TCS1能够结合微管并促进微管组装。进一步研究发现，TCS1可与KCBP/ZWICHEL发生物理相互作用，而KCBP/ZWICHEL是一种参与调控表皮毛分支数的微管动力蛋白。遗传分析结果显示，针对表皮毛分支数这一性状，kcbp/zwi对tcs1呈现上位性。综上，本研究揭示了一条全新的遗传与分子调控机制：TCS1通过与KCBP相互作用，调控微管稳定性，进而实现对拟南芥表皮毛细胞形态的调控。