Drought sensitive maize inbred shows more oxidative damage and higher ROS scavenging enzymes, but not glyoxalases than a tolerant one at seedling stage

Abstract

This study was undertaken to unveil the oxidative stress tolerance mechanism in maize seedlings under drought. The level of oxidative stress and involvement of antioxidant and glyoxalase systems were investigated in seedlings of two maize inbreds: P134, a relatively drought tolerant, and P142, a drought susceptible inbred subjected to water deficit for 7 days and then rewatered to reveal the mechanism of oxidative stress tolerance under drought. Water content, chlorophyll (Chl), reactive oxygen species (ROS), lipid peroxidation, methylglyoxal (MG), lipoxygenase (LOX) activity, enzymatic and non-enzymatic antioxidants and glyoxalases status were investigated in the uppermost fully expanded leaves. The superoxide (O2•-) generation rate, hydrogen peroxide (H2O2), lipid peroxidation and MG as well as LOX activity were higher in P142 throughout the drought period. Conversely, relative water content (RWC), Chl, carotenoid (Car) and proline contents were remarkably higher in P134. However, in rewatering, recovery of Chl and Car were higher in P142. The reduced glutathione (GSH), ascorbic acid (ASA) and their redox homeostasis indicated more oxidative damage in P142. The ROS scavenging enzymes like superoxide dismutase (SOD), peroxidase (POD), ascorbate peroxidase (APX) and dehydroascorbate reductase (DHAR) activities were comparatively higher in P142 under drought, while catalase (CAT), monodehydroasacorbate reductase (MDHAR) and glutathione reductase (GR) activities were higher in P134. Though the activity of GST increased in both inbreds, activities of glyoxalase-I (Gly-I) and glyoxalse-II (Gly-II) increased only in P134. In rewatering, activities of most of the enzymes decreased in both inbreds. Taken together, the non-enzymatic antioxidant system was stronger in P134, but the higher SOD, POD, APX, GPX and DHAR activities in P142 suggesting that these enzymes might involve in cellular protection through reducing oxidative damage.