Free sphingobases induce RBOHD-dependent reactive oxygen species production in Arabidopsis leaves

Sphingolipids are implied in several regulatory processes, including cell death. Levels of the free sphingobase t18:0 (phytosphingosine) increase in Arabidopsis in response to the bacterial pathogen Pseudomonas syringae. To gain information on sphingobase-induced signaling, we determined kinetics of leaf reactive oxygen species (ROS) levels and cell death in response to specific sphingobases. t18:0, d18:0 and d17:1, but not d20:0, induced ROS and cell death within 1.5-2h. Early sphingobase-induced ROS production was independent of cell death induction and required the NADPH oxidase Respiratory Burst Oxidase Homolog D (RBOHD). Specific sphingobases can therefore induce cell death and require RBOHD for early ROS induction in plants.