Histone acetylation and reactive oxygen species are involved in the preprophase arrest induced by sodium butyrate in maize roots. 
Histone acetylation plays a critical role in controlling chromatin structure, and reactive oxygen species (ROS) are involved in cell cycle progression.  To study the relationship between histone acetylation and cell cycle progression in plants, sodium butyrate (NaB), a histone deacetylase (HDAC) inhibitor that can cause a significant increase in histone acetylation in both mammal and plant genomes, was applied to treat maize seedlings.  The results showed that NaB had significant inhibition effects on different root zones at the tissue level and caused cell cycle arrest at preprophase in the root meristem zones.  This effect was accompanied by a dramatic increase in the total level of acetylated lysine 9 on histone H3 (H3K9ac) and acetylated lysine 5 on histone H4 (H4K5ac).  The exposure of maize roots in NaB led to a continuous rise of intracellular ROS concentration, accompanied by a higher electrolyte leakage ratio and malondialdehyde (MDA) relative value.  The NaB-treated group displayed negative results in both TdT-mediated dUTP nick end labelling (TUNEL) and γ-H2AX immunostaining assays.  The expression of topoisomerase genes was reduced after treatment with NaB. These results suggested that NaB increased the levels of H3K9ac and H4K5ac and could cause preprophase arrest accompanied with ROS formation leading to the inhibition of DNA topoisomerase.