The cell wall, a defining feature of plants, provides a rigid structure critical for bonding cells together. To overcome this physical constraint, plants must process cell wall linkages during growth and development. However, little is known about the mechanism guiding cell-cell detachment and cell wall remodeling. Here, we identify two neighboring cell types in Arabidopsis that coordinate their activities to control cell wall processing, thereby ensuring precise abscission to discard organs. One cell type produces a honeycomb structure of lignin, which acts as a mechanical "brace" to localize cell wall breakdown and spatially limit abscising cells. The second cell type undergoes transdifferentiation into epidermal cells, forming protective cuticle, demonstrating de novo specification of epidermal cells, previously thought to be restricted to embryogenesis. Loss of the lignin brace leads to inadequate cuticle formation, resulting in surface barrier defects and susceptible to infection. Together, we show how plants precisely accomplish abscission.

Endoplasmic reticulum (ER) has a unique redox environment, which plays critical roles in the organelle's function and in its pathological responses such as ER stress. In this work, we introduce an ER-targeting fluorogenic reactive oxygen species (ROS) chemosensor (ER-Flu) from copper(I)-catalyzed alkyne-azide cycloaddition of 3-propargyl ester of 2 0 ,7 0-dichlorodihydrofluorescein diacetate and N 3-glibenclamide, which were adopted as a fluorogenic ROS sensing module and an ER-targeting module, respectively. Thereby, a series of confocal microscopic experiments of ER-Flu demonstrated that the sensor localizes in ER of the live cells and that ROS are elevated in the cells by ER stress inducers such as thapsigargin, brefeldin A, and tunicamycin.