1 Epigenetic Changes Are Associated with Programmed Cell Death Induced by Heat Stress in Seedling Leaves of Zea mays

Abstract Histone modification plays a crucial role in regulation of chromatin architecture and function responding to adverse external stimuli. However, little is known about a possible relationship between epigenetic modification and programmed cell death (PCD) in response to environmental stress. Here, we found that heat stress induced PCD in maize seedling leaves which was characterized by chromatin DNA laddering and DNA strand breaks detected by a TdT-mediated dUTP nick end labeling (TUNEL) test. The activities of the reactive oxygen species (ROS)-related enzymes, superoxide dismutase (SOD), peroxidase (POD) and catalase (CAT) were progressively increased over time in the heat-treated seedlings. However, the concentration of H2O2 molecule kept relatively lower levels, while the concentration of superoxide anion (O2) was accumulated, accompanied by the occurrence of higher ion leakage rates after heat treatment. The total acetylation levels of histones H3K9, H4K5 and H3 were significantly increased whereas the di-methylation level of histone H3K4 was unchanged and the di-methylation level of histone H3K9 was decreased in the seedling leaves exposed to heat stress compare