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

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 (O2·-) and hydrogen peroxide (HO), show dynamic changes in the shoot apex during the plant life cycle of . We found that the level of O2·- decreased and disappeared at four weeks after bolting (WAB), while HO appeared at 3 WAB and showed a burst at 5 WAB. The timing of dynamic changes in O2·- and HO was delayed for approximately three weeks in , which has a longer lifespan. Moreover, exogenous application of HO inhibited the expression of the stem cell determinant () and promoted the expression of the developmentally programmed cell death (dPCD) marker gene (). These results indicate that HO triggers an important signal inducing dPCD in stem cells. Given that O2·- plays roles in maintaining expression and stem cell activity, we speculate that the dynamic shift from O2·- to HO in the shoot apex results in stem cell death. Our findings provide novel insights for understanding ROS-mediated regulation during plant stem cell death.