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

Zhu, Qiusha, Zhang, Jie, Yu, Haijuan, Li, Liang, Chen, Xi, Jiang, Mingyi, Tan, Mingpu
Environmental and experimental botany 2019 v.158 pp. 171-179
alpha-tocopherol, antioxidants, cadmium, chloroplasts, corn, fluorescence, gamma-tocopherol, heavy metals, heterologous gene expression, leaves, lipophilicity, oxidative stress, plant growth, screening, tobacco, tocopherol O-methyltransferase, toxicity, yeasts
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.