Maize Cd-tolerant ZmVTE4 encoding γ-tocopherol-methyl-transferase alleviated Cd-toxicity through its product α-tocopherol

Abstract

Cadmium (Cd) is a widespread non-essential toxic heavy metal and usually arouses oxidative stress which impairs plant growth. The key lipophilic antioxidant α-tocopherol is synthesized from γ-tocopherol by γ- tocopherol-methyl-transferase (γ-TMT encoded by VTE4) in response to a variety of abiotic stresses.The main purpose of this study was to characterize the Cd-tolerant maize ZmVTE4 which was obtained through high-throughput survival screening in the presence of Cd. Further heterologous expression of a ZmVTE4 enhanced Cd tolerance in yeast as well in tobacco. Moreover, Cd treatment induced the increment of tocopherols in maize leaves. Similarly, transient overexpressing ZmVTE4 increased the content of γ-tocopherol and α-tocopherol thus enhancing the Cd tolerance in tobacco leaves. Visualized fluorescence indicated that ZmVTE4 was localized in chloroplasts, where tocopherols were synthesized. These results collectively implicated that ZmVTE4-mediated α-tocopherol generation facilitated plant tolerance to Cd.