MDH and CAT increase the germination of cryopreserved Paeonia pollen by regulating the ROS and apoptosis-like events

Previous work in our group has shown that malate dehydrogenase (MDH) and catalase (CAT) are expressed differentially in Magnolia and Paeonia pollen following cryopreservation. To study the relationships between differentially expressed proteins, particularly those related to reactive oxygen species (ROS) and apoptosis-like events, and pollen cryopreservation, we determined changes in germination, ROS level, caspase-3-like activity and apoptosis-like responses in Paeonia lactiflora ‘Hong Pan Tuo Jin’ and ‘Fen Yu Nu’ pollen with or without MDH or CAT added. Pollen from ‘Hong Pan Tuo Jin’ showed a great loss of viability, but marked increase of ROS level and caspase-3-like activity after cryopreservation. Caspase-3-like/protein and apoptosis-like rates remained unchanged. MDH addition improved the post-LN pollen viability significantly, decreased the ROS level, caspase-3-like activity and caspase-3-like/protein, but had no effect on the apoptosis-like rate. Pollen from ‘Fen Yu Nu’ showed a slight decrease in germination, marked increase in ROS level and apoptosis-like rate, and unchanging pollen viability, caspase-3-like activity and caspase-3-like/protein. CAT addition significantly increased the post-LN pollen viability, and greatly decreased the apoptosis-like rate. ROS level was also decreased, but caspase-3-like activity and caspase-3-like/protein did not change. In conclusion, MDH and CAT may increase the post-LN pollen germination by regulating the ROS and apoptosis-like events, but through different routes. By reducing ROS and caspase-3-like activity, MDH stabilized apoptosis-like activity. CAT may increase the cryopreservation pollen germination by directly reducing apoptosis-like events and ROS.