Oxidative damage and antioxidative indicators in 48 h germinated rice embryos during the vitrification-cryopreservation procedure.

KEY MESSAGES: Cu/Zn SOD and other genes may be critical indicators of a stress response to reactive oxygen species (ROS) accumulation in 48 h germinated rice embryos subjected to vitrification cryopreservation. In the current study, reactive oxygen species (ROS) accumulation was investigated in 48 h germinated rice embryos during the vitrification-cryopreservation process. We found that vitrification-cryopreservation significantly affected ROS levels, especially superoxide anion levels, in 48 h germinated rice embryos. Malonaldehyde content in the apical meristems of germinated embryos was significantly positively correlated with the rate of superoxide anion generation and the highest levels of malonaldehyde content were reached after vitrification treatment. Cell viability in 48 h germinated embryos was significantly negatively correlated with the rate of superoxide anion generation, malonaldehyde content, and electrolyte leakage. Spatial and temporal patterns in ROS accumulation in these embryos existed during the vitrification procedure. Among the vitrification-cryopreservation treatments we assessed, the preculture treatment was found to stimulate superoxide anion generation and to activate the response system in the apical meristems of germinated embryos. Loading treatments motivated the catalase and ascorbate peroxidase activities. During the vitrification-dehydration treatment, oxidative stress reached the highest levels causing an antioxidative response. This response involved antioxidant enzymes promoting detoxification of ROS. Based on a comprehensive correlation analysis involving ROS accumulation, cell viability, the activities of antioxidant enzymes, and gene expression profiles, Cu/Zn SOD, CAT1, APX7, GR2, GR3, MDHAR1, and DHAR1 may be critical indicators of oxidative stress affected by the vitrification-cryopreservation treatments. The investigation of these antioxidative responses in 48 h germinated rice embryos may, therefore, provide useful information with respect to plant vitrification-cryopreservation.