Reactive oxygen species in leaf abscission signaling.

Reactive oxygen species (ROS) are produced in response to many environmental stresses, such as UV, chilling, salt and pathogen attack. These stresses also accompany leaf abscission in some plants, however, the relationship between these stresses and abscission is poorly understood. In our recent report, we developed an in vitro abscission system that reproduces stress-induced pepper leaf abscission in planta. Using this system, we demonstrated that continuous production of hydrogen peroxide (H(2)O(2)) is involved in leaf abscission signaling. Continuous H(2)O(2) production is required to induce expression of the cell wall-degrading enzyme, cellulase and functions downstream of ethylene in abscission signaling. Furthermore, enhanced production of H(2)O(2) occurs at the execution phase of abscission, suggesting that H(2)O(2) also plays a role in the cell-wall degradation process. These data suggest that H(2)O(2) has several roles in leaf abscission signaling. Here, we propose a model for these roles.