Dynamic Changes in Reactive Oxygen Species in the Shoot Apex Contribute to Stem Cell Death in Arabidopsis thaliana

In monocarpic plants, stem cells are fated to die. However, the potential mechanism of stem cell death has remained elusive. Here, we reveal that the levels of two forms of reactive oxygen species (ROS), superoxide anion free radical ([Formula: see text]) and hydrogen peroxide (H(2)O(2)), show dynamic changes in the shoot apex during the plant life cycle of Arabidopsis thaliana. We found that the level of [Formula: see text] decreased and disappeared at four weeks after bolting (WAB), while H(2)O(2) appeared at 3 WAB and showed a burst at 5 WAB. The timing of dynamic changes in [Formula: see text] and H(2)O(2) was delayed for approximately three weeks in clv3-2, which has a longer lifespan. Moreover, exogenous application of H(2)O(2) inhibited the expression of the stem cell determinant WUSCHEL (WUS) and promoted the expression of the developmentally programmed cell death (dPCD) marker gene ORESARA 1 (ORE1). These results indicate that H(2)O(2) triggers an important signal inducing dPCD in stem cells. Given that [Formula: see text] plays roles in maintaining WUS expression and stem cell activity, we speculate that the dynamic shift from [Formula: see text] to H(2)O(2) in the shoot apex results in stem cell death. Our findings provide novel insights for understanding ROS-mediated regulation during plant stem cell death.