Differential Status of Polyamine Metabolism in Wild Maize and Derived Lines during Waterlogging Stress

The present investigation was undertaken to evaluate the status of polyamine metabolism in teosinte and derived lines during waterlogging stress. Maize genotypes, CM-140 and I-172 (relatively susceptible and tolerant checks, respectively), teosinte (wild progenitor) and derived lines (DL-1, DL-2, DL-3, DL-4, DL-5, DL-6 and DL-7) were taken for the study. Seedling growth, activities of polyamine oxidase (PAO), diamine oxidase (DAO), arginine decarboxylase (ADC), ornithine decarboxylase (ODC) and contents of polyamines (putrescine, spermidine and spermine) were determined during waterlogging. Teosinte showed unaffected growth parameters except for a little decrease in shoot length, during waterlogging stress. Seedling growth remained unaffected in waterlogged DL-4 seedlings while DL-1 and DL-2 showed decrease in all the growth parameters. Polyamine content increased in the roots and shoots of all the genotypes under hypoxic conditions. Other lines acclimatize to waterlogging stress by maintaining their dry matter content but varied in their tolerance mechanism with relation to polyamine metabolizing enzymes. The increased expressions of ZmPAO6, ZmDAO and ZmADC1 genes in the hypoxic roots of DL-4 seedlings corresponded to the increased enzymatic activities. Principal component analysis (PCA) and Pearson correlation coefficient showed that the contents of putrescine, spermidine, and spermine and activities of ADC and ODC in hypoxic roots contributed significantly towards waterlogging response of the plants. PCA showed that the polyamine synthesizing and catabolizing enzymes of roots are closely associated with the tolerance behavior of DL-4 seedlings. It may be inferred that the maximum tolerance shown by DL-4 in terms of unaltered seedling growth might be due to polyamine modulated sustainable root development, under waterlogging conditions. To the best of our knowledge, this is the first report about the polyamine status of wild maize and derived lines that could be used in breeding waterlogging tolerant maize genotypes.