Ascorbate-dependent hydrogen peroxide detoxification and ascorbate regeneration during germination of a highly productive maize hybrid: Evidence of an improved detoxification mechanism against reactive oxygen species

Ascorbate content and the activities of some key enzymes involved in the de toxification from reactive oxygen species were investigated in germinated e mbryos of two Zea mays L, inbred lines (B73 and Mo17) and of their heteroti c F1 hybrid (B73 x Mo17). The F1 hybrid showed a higher ascorbate biosynthe tic capability owing to a higher activity of L-galactono-gamma-lactone dehy drogenase (EC 1,6,5,4), the last enzyme in ascorbate biosynthesis. Ascorbat e peroxidase (EC 1,11.1,11), ascorbate free radical reductase (EC 1.6.5.4) and dehydroascorbate reductase (EC 1.8.5.1) activities were much higher in the F1 hybrid than in either inbred line, whereas catalase (EC 1.11.1.6) ac tivity was similar in the three genotypes, Native polyacrylamide gel electr ophoresis (PAGE) analysis showed three forms of cytosolic ascorbate peroxid ase, both in parental lines and in the FI hybrid. On the other hand, a comp lex pattern of proteins with dehydroascorbate reductase activity was observ ed, with the hybrid combining the different dehydroascorbate-reducing prote ins expressed by the inbred lines. The possible involvement of the enzymes of the ascorbate system in the phenomenon of hybrid vigour is discussed.