Abstract
To study signaling mechanisms involved in leaf abscission in Capsicum plants, we developed an in vitro abscission system. Microscopic analysis revealed reactive oxygen species (ROS) were constitutively produced by the abscission zone (AZ) cells. ROS scavengers and diphenylene iodonium (DPI), an inhibitor of NADPH oxidase, suppressed the in vitro abscission and cellulase expression. Conversely, application of ROS promoted in vitro abscission and expression of cellulase. Ethephon-induced abscission accompanied the production of ROS at the AZ and this abscission was suppressed by the inhibitors of ROS. During in vitro abscission, expression of upregulated ethylene-responsive genes was unaffected by the ROS or ROS inhibitor. These indicate that ROS act downstream from ethylene in the in vitro abscission signaling. In planta, salinity induced expression of the ROS-responsive genes and ROS production at the AZ, which preceded leaf abscission, indicating that ROS have roles in leaf abscission.
