Expression of tobacco tocopherol cyclase in rice regulates antioxidative defense and drought tolerance

Abstract

Tocopherols (α-, β-, γ-, and δ-tocopherol) represent a group of lipophilic antioxidants that are synthesized only by photosynthetic organisms. It is widely believed that the main functions of tocopherols are protection of pigments and proteins of photosystem and polyunsaturated fatty acids from oxidative damage caused by reactive oxygen species. In the present study, we report on the cloning and characterization of NtTC, which is a tocopherol cyclase (TC) ortholog isolated from tobacco. To enhance tocopherol contents, we generated independent transgenic rice events in expressing NtTC or NtTC along with Perilla γ-tocopherol methyltransferase genes. The transgenic TC line significantly increased α-, total tocopherol, total glutathione, and total antioxidant status activity levels compared with the wild type. Furthermore, TC rice plants showed higher tolerance to drought than wild-type rice plants. On the basis of these studies, we concluded that overexpression of NtTC could increase the tolerance to drought stress and that the increase in tocopherol affects cellular signaling and antioxidant defense of plants in response to drought.