Aluminum-induced cell death in root-tip cells of barley

Abstract

Aluminum-induced cell death was investigated in root-tip cells of barley ( Hordeum vulgare). The growth of roots in 0.1–50 mM Al treatments was inhibited after 8 h treatments, and could not be recovered after 24 h recovery culture without Al. Viable detection with fluorescein diacetate–propidium iodide (FDA–PI) staining shows that most of the root-tip cells have lost viability. These results suggest that the irreversible inhibition of root growth after 8 h Al treatments or 24 h recovery culture is mainly caused by cell death. DNA ladders occurred in root tips only after 8 h Al treatments (0.1–1.0 mM), but no apoptotic bodies in root tips were observed. Thus, the cell death caused by Al stress is likely to be Al-induced programmed cell death (PCD). The reactive oxygen species (ROS) in root-tip cells measured by ultraweak luminescence indicated that the oxidation status in root-tip cells basically ceased after exposure to 10–50 mM Al for 24 h, but was very violent in the root-tip cells treated with 0.1–1.0 mM for 24 h. Exposure to 0.1–1.0 mM Al for 3–12 h led to ROS burst. Therefore, our results suggest that 0.1–1.0 mM Al treatments for 8 h induce cell death (Al-induced PCD) possibly via a ROS-activated signal transduction pathway, whereas 10–50 mM Al treatments may cause necrosis in the root-tip cells. These results have an important role for further studies on the mechanism of Al toxicity in plants.