Abstract
The NAC (NAM, ATAFs, CUC) family of transcription factors (TFs) play a pivotal role in regulating all processes of the growth and development of plants, as well as responses to biotic and abiotic stresses. Yet, the functions of NACs from non-model plant species remains largely uncharacterized. Here, we characterized the stress-responsive effects of a NAC gene isolated from wintersweet, an ornamental woody plant that blooms in winter when temperatures are low. CpNAC68 is clustered in the NAM subfamily. Subcellular localization and transcriptional activity assays demonstrated a nuclear protein that has transcription activator activities. qRT-PCR analyses revealed that CpNAC68 was ubiquitously expressed in old flowers and leaves. Additionally, the expression of CpNAC68 is induced by disparate abiotic stresses and hormone treatments, including drought, heat, cold, salinity, GA, JA, and SA. Ectopic overexpression of CpNAC68 in Arabidopsis thaliana enhanced the tolerance of transgenic plants to cold, heat, salinity, and osmotic stress, yet had no effect on growth and development. The survival rate and chlorophyll amounts following stress treatments were significantly higher than wild type Arabidopsis, and were accompanied by lower electrolyte leakage and malondialdehyde (MDA) amounts. In conclusion, our study demonstrates that CpNAC68 can be used as a tool to enhance plant tolerance to multiple stresses, suggesting a role in abiotic stress tolerance in wintersweet.
Highlights
Plants have evolved complex responses to mitigate the effects of abiotic stresses
The N-terminal NAC domain has an abundance of positive charges that are believed to enable the one side of the protein dimer to directly bind to DNA [8]
Multiple sequence alignment showed that the N-terminal half of CpNAC68 has the conserved domain, including A, B, C, D, and E subdomains [8], while the C-terminal half is highly divergent (Figure 1A)
Summary
Plants have evolved complex responses to mitigate the effects of abiotic stresses. These include long-term physiological adaptations, such as changes in stature and lifecycle, and rapid molecular responses that alleviate the damaging effects of stress [1]. NAC proteins regulate genes by directly binding specific cis-acting DNA elements to activate or repress gene expression at the transcription level [5,6]. Compared with the typical helix-turn-helix structure of DNA binding, NAC TF proteins have unique domain characteristics [7]. All proteins in this family share a conserved N-terminal NAC domain, containing A, B, C, D, E subdomains. Nuclear localization signals in the C and D sub-region sequences may be involved in binding cis-acting elements [7]
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