Temporal changes in surface tension guide microtubule organization and accurate asymmetric division of Arabidopsis zygotes

In most plants, the zygote divides asymmetrically to define the body axis. In Arabidopsis thaliana, the zygote undergoes polar cell elongation with maintaining a transverse band of cortical microtubules (MTs) at the growing cell tip. How the MT band is maintained at the actively renewing tip and whether it contributes to the asymmetric zygote division remain elusive. By combining live-cell imaging, mechanical simulation, and various perturbation analyses, we demonstrate a bidirectionally interactive feedback in which the MT band forms a mechanical frame to support polar zygote elongation, and this growth increases the calculated surface tension at the zygote tip to induce MT band formation. Furthermore, after zygote elongation is complete, the MT band guides another MT band, preprophase band, to determine the accurate cell division site. Therefore, the MT band is maintained via mechanical feedback with polar cell growth, ensuring the proper asymmetric cell division of the zygote. Kang et al. demonstrate that mechanical feedback between surface tension and microtubules underlies polar growth of Arabidopsis zygotes. This feedback also ensures asymmetric cell division that establishes the plant body axis.