Single-cell transcriptomics of the Arabidopsis floral abscission zone

Abstract

AbstractAbscission is the programmed separation of plant organs. It is widespread in the plant kingdom with important functions in development and environmental response. In Arabidopsis, abscission of floral organs (sepals, petals, and stamen) is controlled by two related receptor-like protein kinases HAESA/HAE and HAESA LIKE-2/HSL2, which are thought to orchestrate the programmed dissolution of the pectin-rich middle lamella between cells in the abscission zone, as well as the remodeling of the cell wall that occurs during abscission. Here, we report transcriptional characterization of the abscission zones of WT and the abscission deficient hae hsl2 double mutant at single-cell resolution. We identify core abscission gene expression programs, as well as perturbations of differentiation dynamics in hae hsl2, including detecting expression changes in distinct spatial domains of the abscission zone. We also report identification of a novel negative regulator of abscission signaling, MAP KINASE PHOSPHATASE-1/MKP1. Mutating MKP1 partially suppresses the abscission defect of hae hsl2. We establish the molecular basis of the suppression as reactivation of the HAE/HSL2 pathway. Our results provide deep insight into the biology of abscission and establish it as a model developmental signaling system for interrogation by single-cell technologies.