Arsenate (AsV) stress response in maize (Zea mays L.)

• Impact of arsenate (AsV) stress was assessed on maize seedling.
• High dose of AsV (≥50 μM) treatment caused severe oxidative burst.
• High GR expression and GSH/GSSG ratio could not protect cells from oxidative damages.
• Decreased DHAR and MDAR render stressed cells in futile recycling of ascorbate pool.
• High PC synthesis in root might restrict arsenic translocation from root to shoot.

The present study assesses the impact of arsenate (AsV) stress on maize (Zea mays L.) seedlings. Three different levels of AsV stress (25, 50 and 100 μM Na2HAsO4·7H2O) were imposed and seedling growth performances were studied at 2d and 4d of experiment. Arsenate induced modulation of antioxidant enzymes of ascorbate-glutathione cycle along with antioxidant molecules (glutathione and ascorbate) were monitored. Dose and time dependent decline in shoot biomass along with yellowing and drying of leaf tips were observed in AsV treated seedlings. Comparatively high phytochelatin synthesis in roots appears to restrict arsenic translocation from root to aboveground tissues as evident from low arsenic concentration in leaves as compared to roots. Increased uptake of Evans blue by AsV stressed roots indicates loss of root cells viability. Histochamical staining with NBT and DAB revealed dark blue and brown spots respectively on the leaves under AsV stress, which indicated oxidative burst. CM-H2DCFDA and DHE staining of AsV stressed roots further indicated enhanced formation of ROS. Western blot and real-time qRT-PCR analyses revealed high GR expression at protein and transcript levels respectively in presence of high AsV concentration. However, increased GR activity coupled with high GSH/GSSG ratio and enhanced GST activity does not seem to prevent cells from oxidative damages, as evident from high MDA level in leaves of 50 and 100 μM AsV stressed seedlings. Marked decrease in DHAR and MDAR render the stressed cells in futile recycling of ascorbate pool which might contribute to increased susceptibility towards high AsV dose.