Temporal changes in surface tension guide the accurate asymmetric division of Arabidopsis zygotes

Abstract

In most plants, the zygote divides asymmetrically to define the body axis. In Arabidopsis thaliana, the zygote undergoes polar elongation maintaining a transverse band of cortical microtubules (MTs), and divides asymmetrically forming another MT band, preprophase band (PPB). How the MT band is maintained at the actively growing cell tip and whether it contributes to PPB formation remain elusive. By combining live-cell imaging and mechanical simulation, we show that zygote elongation induces a temporal change (large material derivative) in surface tension at the growing tip to maintain the MT band, which in turn supports polar elongation. The MT band then guides PPB to determine the cell division site. Therefore, autonomous mechanical feedback between cell elongation and MT organization ensures the zygote division asymmetry.