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. 2015 Nov 4;15:268.
doi: 10.1186/s12870-015-0644-9.

TaNAC29, a NAC Transcription Factor From Wheat, Enhances Salt and Drought Tolerance in Transgenic Arabidopsis

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Free PMC article

TaNAC29, a NAC Transcription Factor From Wheat, Enhances Salt and Drought Tolerance in Transgenic Arabidopsis

Quanjun Huang et al. BMC Plant Biol. .
Free PMC article

Abstract

Background: NAC (NAM, ATAF, and CUC) transcription factors play important roles in plant biological processes, including phytohormone homeostasis, plant development, and in responses to various environmental stresses.

Methods: TaNAC29 was introduced into Arabidopsis using the Agrobacterium tumefaciens-mediated floral dipping method. TaNAC29-overexpression plants were subjected to salt and drought stresses for examining gene functions. To investigate tolerant mechanisms involved in the salt and drought responses, expression of related marker genes analyses were conducted, and related physiological indices were also measured. Expressions of genes were analyzed by quantitative real-time polymerase chain reaction (qRT-PCR).

Results: A novel NAC transcription factor gene, designated TaNAC29, was isolated from bread wheat (Triticum aestivum). Sequence alignment suggested that TaNAC29 might be located on chromosome 2BS. TaNAC29 was localized to the nucleus in wheat protoplasts, and proved to have transcriptional activation activities in yeast. TaNAC29 was expressed at a higher level in the leaves, and expression levels were much higher in senescent leaves, indicating that TaNAC29 might be involved in the senescence process. TaNAC29 transcripts were increased following treatments with salt, PEG6000, H2O2, and abscisic acid (ABA). To examine TaNAC29 function, transgenic Arabidopsis plants overexpressing TaNAC29 were generated. Germination and root length assays of transgenic plants demonstrated that TaNAC29 overexpression plants had enhanced tolerances to high salinity and dehydration, and exhibited an ABA-hypersensitive response. When grown in the greenhouse, TaNAC29-overexpression plants showed the same tolerance response to salt and drought stresses at both the vegetative and reproductive period, and had delayed bolting and flowering in the reproductive period. Moreover, TaNAC29 overexpression plants accumulated lesser malondialdehyde (MDA), H2O2, while had higher superoxide dismutase (SOD) and catalase (CAT) activities under high salinity and/or dehydration stress.

Conclusions: Our results demonstrate that TaNAC29 plays important roles in the senescence process and response to salt and drought stresses. ABA signal pathway and antioxidant enzyme systems are involved in TaNAC29-mediated stress tolerance mechanisms.

Figures

Fig. 1
Fig. 1
Expression patterns of TaNAC29 in wheat after stress treatments. Expression patterns of TaNAC29 in wheat leaves and roots after NaCl, PEG6000, ABA and H2O2 treatments by qRT-PCR analysis. Leaf and root were collected after different stress treatment. The 2−ΔΔCT method was used in qRT-PCR analysis. Transcript levels were normalized to TaActin. Values are means ± SE of three replicates. Asterisks indicate statistically significant differences from mock (*P < 0.05; **P < 0.01). Three independent experiments were performed
Fig. 2
Fig. 2
The TaNAC29-overexpression (OE) lines have enhanced tolerance to salt and drought stress. a Phenotypes of WT, VC (vector control) and OE plants grown on salt soil supplemented with 250 mM NaCl in different growth stage, including (I) 25-day-old seedling, (II) 45-day-old seedling and (III) 65-day-old seedling. b Phenotypes of WT, VC and OE plants treated with drought stress at different growth stage, including (I) 25-day-old seedling and (II) 65-day-old seedling. c Quantitative analysis of survival rate of 25-day-old seedling after salt and drought stresses. Values are means ± SE of three replicates. Asterisks indicate statistically significant differences from WT (**P < 0.01)
Fig. 3
Fig. 3
Root length assays of WT, VC (vector control) and overexpression (OE) lines. a Phenotypes of WT, VC and OE plants grown for 8 d on medium supplemented with 0 or 120 mM NaCl (I) and primary root length (II). b Phenotypes of WT, VC and OE plants grown for 8 and 16 d on medium supplemented with 0 or 400 mM Mannitol (I) and primary root length (II). Values are means ± SE (n = 20 to 25 plants) in root length assays. Asterisks indicate statistically significant differences from WT (*P < 0.05, **P < 0.01)
Fig. 4
Fig. 4
Hypersensitivity of TaNAC29-overexpression (OE) lines to ABA. a Phenotypes of WT, VC (vector control) and OE plants grown for 8 d on medium supplemented with 0 or 10 μM ABA (I) and primary root length (II). Values are means ± SE (n = 20 to 25 plants). Asterisks indicate statistically significant differences from WT (*P < 0.05). b Seedlings of WT, VC and TaNAC29-overexpression lines observed 8 d after germination on 1/2 MS medium supplemented with 0 or 2 μM ABA (I) and quantitative analysis of seedling emergence rate (II). Values are means ± SE (n = 60 to 90 seeds). Asterisks indicate statistically significant differences from WT (**P < 0.01). Comparison of root length of WT, VC and TaNAC29-overexpression lines (III). Three independent experiments were performed, each evaluating 60 to 90 seeds
Fig. 5
Fig. 5
Expression pattern of relevant genes (a RD29bb SAG13c SAG113d AIB1e ERD11, and f ABI5) in WT and TaNAC29-overexpression (OE) plants. Seedlings of WT and OE were treated with 250 mM salt stress for 10 d and drought stress for 17 d, respectively. Total RNAs were extracted from leaves, and qRT-PCR analysis was performed. The 2−ΔΔCT method was used in qRT-PCR analysis. Values are means ± SE of three replicates. Asterisks indicate statistically significant differences from WT (*P < 0.05; **P < 0.01). Three independent biological experiments were performed
Fig. 6
Fig. 6
Analysis of physiological indices under salt stress conditions. Analysis of chlorophyll content (a), electrolyte leakage (b), MDA content (c), H2O2 content (d) and SOD (e), CAT (f), POD (g) activities in WT and TaNAC29-overexpression (OE) lines under normal and 250 mM salt stress conditions. Seedlings leaves were sampled from WT and TaNAC29-overexpression lines at 0 (as a negative control), 10, 21 or 28 DAT to detect physiological indices. Values are means ± SE of three replicates. Asterisks indicate statistically significant differences from WT (*P < 0.05; **P < 0.01)
Fig. 7
Fig. 7
Analysis of physiological indices under drought stress conditions. Analysis of H2O2 content (a), electrolyte leakage (b), MDA content (c) and SOD (d), CAT (e), POD (f) activities in WT and TaNAC29-overexpression (OE) lines under normal and drought stress conditions. Seedlings leaves were sampled from WT and TaNAC29-overexpression lines at 0 (as a negative control) and 17 DAT to detect physiological indices. Values are means ± SE of three replicates. Asterisks indicate statistically significant differences from WT (*P < 0.05)

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