Overexpression of two cold-responsive ATAF-like NAC transcription factors from fine-stem stylo (Stylosanthes guianensis var. intermedia) enhances cold tolerance in tobacco plants
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Stylosanthes (stylo) species are economically important tropical and subtropical forage legumes. They are vulnerable to chilling and frost, and little is known about the genetic and molecular mechanisms of their responses or adaptations to low temperature stress. Two cold-responsive NAC genes, SgNAC1 and SgNAC2, were selected from a whole transcriptome profiling study of fine-stem stylo (S. guianensis var. intermedia) and further investigated for their roles in cold stress tolerance. Bioinformatic analysis indicated that SgNAC1 and SgNAC2 belonged to ATAF subgroup of NAC family, and shared highly conserved N-terminal A–E NAC subdomains and a EVQS[E/x]PK[W/I] motif with ATAF-like NAC transcription factors. Expression profiling, subcellular location and transactivation assay revealed that SgNAC1 and SgNAC2 encode nucleus-localized polypeptides with transactivation activities and responds promptly to cold stress. Phenotypic and physiological changes indicated that the transgenic tobacco plants overexpressing SgNAC1 and SgNAC2 were more tolerant to cold stress than the wild-type plants. Meanwhile, the expression of SgNAC1 and SgNAC2 were significantly enhanced at the early stages of cold treatment, indicating that overexpression of SgNAC1 and SgNAC2 is sufficient to confer cold tolerance to tobacco plants. These results suggest that SgNAC1 and SgNAC2 are promising candidate genes for cold tolerance improvement strategies in stylo.
KeywordsNAC transcription factor ATAF Cold tolerance Fine-stem stylo Overexpression Expression profiling
[No apical meristem (NAM), Arabidopsis transcription activation factor (ATAF), cup-shaped cotyledon (CUC)]
- MS medium
Murashige and Skoog medium
Green fluorescent protein
- YPDA medium
Yeast, peptone, dextrose and adenine medium
Financial support from the National Natural Science Foundation of China (Nos. 31601990, 31272491 and 31802116) is gratefully acknowledged.
XMX conceived and initiated the project. PLZ and SWK designed and performed most of the experiments and data analysis. PLZ and SC wrote the article; XQZ and BLF participated in plasmid construction, plant transformation and physiological determination; SC, TXZ, LL and PYZ conducted the data collection and bioinformatic analysis.
The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.
Compliance with ethical standards
Conflict of interest
The authors declare that they have no conflict of interest.
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