Effects of 5-Azacytidine (AZA) on the Growth, Antioxidant Activities and Germination of Pellicle Cysts of Scrippsiella acuminata (Dinophyceae)

In this study, we investigated the effects of different concentrations of 5-azacytidine (AZA), a DNA methyltransferase inhibitor, on the growth, antioxidant activities and germination of pellicle cysts of Scrippsiella acuminata . The purpose of this study is to understand the toxic effects of AZA on marine microalgae, and to demonstrate the effect of DNA methyltransferase inhibitors on the germination of pellicle cysts. Results showed that AZA inhibited the growth of S. acuminata significantly, and displaced a clear dose-dependent inhibition trend with the 96h EC 50 of 146.77µmolL −1 (35.84 mg L −1 ). Pellicle cysts of S. acuminata were less sensitive to AZA than the vegetative cells, and the EC 50 value of AZA to the germination of pellicle cysts of S. acuminata was 8.08mmolL −1 (1.97g L −1 ). After exposed to AZA, the antioxidant activities in S. acuminata responded rapidly and significantly. Among them, soluble protein and superoxide dismutase (SOD) were more sensitive to AZA, and significant promotions occurred after exposed to 10 µmolL −1 AZA for 24 h. Meanwhile, malondialdehyde (MDA) contents in algal cells did not change significantly after exposed to low concentrations of AZA, but increased firstly and then decreased under high concentration of AZA. The glutathione (GSH) levels in S. acuminata increased significantly under high concentrations of AZA, and remained unchanged at low concentrations of AZA. The results suggested that the enhanced protein level and SOD activity of S. acuminata eliminated reactive oxygen species (ROS) to a certain extent, and thus protected algal cells against damages of ROS caused by AZA.