Accumulation and phytotoxicity of microcystin-LR in rice (Oryza sativa)

Irrigation with eutrophic water containing microcystins-LR (MC-LR) poses a potential risk to crops. However, the accumulation of MC-LR in rice grains and the mechanism of MC-LR-induced inhibition in rice roots are not understood. In this study, we detected the accumulation of MC-LR in rice grains collected from Taihu Lake region. MC-LR could accumulate in rice grains, but the risk evaluation suggested that MC-LR levels in rice grains from Taihu Lake region may not pose a threat to human health currently. In addition, MC-LR with low concentrations did not affect the growth of rice roots. However, MC-LR with high concentrations impeded the rice root morphogenesis by inhibiting root elongation, crown root formation, and lateral root development from primordia. Treatment with high concentrations of MC-LR stimulated the production of reactive oxygen species (ROS) and inhibited the production of nitric oxide (NO) in rice roots. Exogenous NO treatment reversed the inhibition of rice root growth under MC-LR stress. These results indicated that ROS and NO played important roles in the development of rice roots in responding to MC-LR stress.