Quanjun Huang, Yan Wang, Bin Li, Junli Chang, Mingjie Chen, Kexiu Li, Guangxiao Yang and Guangyuan He

BMC Plant Biology 4 November 2015, 15:268  doi:10.1186/s12870-015-0644-9

http://www.biomedcentral.com/1471-2229/15/268

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, H ₂ O ₂ , 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), H ₂ O ₂ , 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.

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)