Precision abscission for cell surface integrity and plant fitness

Abstract

Organ separation, or abscission, in plants is critical for discarding leaves, flowers, and to conserve resources, and as a form of defense. Little is known about the mechanism guiding the spatiotemporal precision of abscission, nor how protection of the newly formed surface is maintained. Here, we identify two neighboring cell types in Arabidopsis that coordinate their activities to ensure precise organ abscission. One cell type produces a honeycomb structure of lignin, which acts as a mechanical brace to localize cell wall breakdown and spatially restrict abscising cells. The second cell type forms a layer of new epidermis with a protective cutin coat, defects in which lead to an imperfect surface barrier susceptible to infection. This transdifferentiation event demonstrates de novo specification of epidermal cell identity, which was thought to be restricted to embryogenesis.