ER-related E2-E3 ubiquitin enzyme pair regulates ethylene response by modulating the turnover of ethylene receptors.

Gaseous phytohormone ethylene regulates various aspects of plant development. Ethylene is perceived by ER membrane-localized receptors, which are inactivated upon binding with ethylene molecules, thereby initiating ethylene signal transduction. Here, we report that a novel E3 ligase RING finger for Ethylene receptor Degradation (RED) and its E2 partner UBC32 ubiquitinate ethylene-bound receptors for degradation through an ER associated degradation (ERAD) pathway in both Rosa hybrida and Solanum lycopersicum. The depletion of RED or UBC32 leads to hypersensitivity to ethylene, which is manifested as premature leaf abscission and petal shedding in roses, as well as the dwarf plants and accelerated fruit ripening in tomatoes. Disruption of the conserved ethylene binding site of receptors prevents RED-mediated degradation of the receptors. Our study discovers an ERAD branch that facilitates the ethylene-induced degradation of receptors, and provides insights into how the plant's response to ethylene can be controlled by modulating the turnover of ethylene receptors.