Maize annexin genes ZmANN33 and ZmANN35 encode proteins that function in cell membrane recovery during seed germination

Plasma membrane (PM) recovery from the impaired dry state is essential for seed germination, but its underlying mechanism remains unclear. In this study, we found that ZmANN33 and ZmANN35, two annexin genes in maize, encode proteins that participate in PM recovery during seed germination. The expression of both genes was upregulated during seed germination and strongly repressed by chilling (either 15 or 5 degrees C) as compared with the normal temperature (25 degrees C). In addition, the increased membrane damage caused by chilling imbibition was correlated with suppressed expression of ZmANN33 and ZmANN35, while rapid recovery of their expression levels accompanied the rescue of the damaged membrane. Arabidopsis seedlings ectopically expressing ZmANN33 or ZmANN35 had longer seedling length than wild-type (WT) plants during the recovery period after 3 d of chilling stress, indicating the positive roles of these two gene products in the plant's recovery from chilling injury. Moreover, these transgenic seedlings had lower lipid peroxidation and higher peroxidase activities than WT during the recovery period. Consistently, root cells of these transgenic seedlings had more intact PM after chilling stress, supporting the proposition that ZmANN33 and ZmANN35 contribute to the maintenance of PM integrity. The enhanced PM integrity is likely due to the accelerated exocytotic process after chilling stress. We also showed that both ZmANN33 and ZmANN35 localized in the cytosol near the plasma membrane. Thus, we conclude that ZmANN33 and ZmANN35 play essential roles in membrane recovery during maize seed germination.