Overexpression of the Transcription Factor NtNAC2 Confers Drought Tolerance in Tobacco
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NAC proteins constitute one of the largest families of plant-specific transcription factors and play an important role in biological processes, including plant development and phytohormone homeostasis, and in responses to various environmental stresses. In this study, we isolated an NAC group A gene (named NtNAC2) from Nicotiana tabacum L. Quantitative RT-PCR (qRT-PCR) analysis indicated that NtNAC2 was significantly upregulated under drought stress, which implied NtNAC2 was important in tobacco under such conditions. Overexpression of NtNAC2 in tobacco plants exhibited enhanced drought tolerance by means of improved seedling growth. Under drought stress, organic osmoprotectants were significantly accumulated in these plants. Additionally, the activities of antioxidant defense enzymes, like superoxide dismutase (SOD) and peroxidase (POD), which could effectively scavenge accumulated reactive oxygen species (ROS), increased in NtNAC2-overexpression transgenic tobacco plants compared with wild-type plants. The net photosynthetic rate was also significantly increased in NtNAC2-overexpression transgenic lines compared with wild-type plants, and the content of malondialdehyde (MDA) and proline was lower in NtNAC2-overexpression transgenic lines than that in wild-type plants (P < 0.01). Furthermore, the expression of NtWRKY28, a drought resistance gene, was significantly increased and the δ-OAT gene was downregulated in NtNAC2-overexpression plants relative to wild-type plants. Taken together, these results indicated that NtNAC2 functions as a positive regulator of drought stress tolerance. This study provides a basis for further study of drought resistance conferred by the NtNAC2 gene.
KeywordsNtNAC2 Antioxidant defense Drought resistance Nicotiana tabacum
This work was funded by the National Natural Science Foundation (No. 31160149) and by the Major Projects of National New Varieties of Genetically Modified Organisms.
(No. 2014ZX08010-003-2016ZX08010-003). The authors thank Litang Lu for the technical assistance.
Author Contribution Statement
XX and YX designed and conducted the experiments. XX wrote the manuscript. LL contributed by helping with some experiments presented in the manuscript. LL helped to edit the manuscript. LL and ZD supervised the studies and revised the manuscript. All authors read and approved the manuscript.
Compliance with Ethical Standards
Conflict of Interest
The authors declare that they have no conflict of interest.
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