|Other Abstract||NAC (NAM, ATAF1/2 and CUC2) transcription factors, which distribute widely in many land plant species, constitute one of the largest families of plant-specific transcription factors. The NAC family members have a highly conserved NAC domain in N-terminal ends with about 150 amino acids and a variable transcriptional regulatory region in the C-terminal region. NAC TFs have been found to participate in various processes, including flower development, formation of secondary walls and cell division, shoot apical meristem formation, leaf senescence, as well as biotic and abiotic stress responses.
In our previous study, a NAC gene from Tamarix hispida that is respond to salt stress was identified, and named ThNAC7 (GenBank number: JQ974961). Yeast two-hybrid analysis revealed that ThNAC7 has transcription activity, and the transcription activity domain locates in its C-terminal constituted by three independent transcription activity domains. The 35S:ThNAC7 expression vector was constructed and transformed into Arabidopsis, and T3 transgenic lines with overexpressing ThNAC7 was used in study. Measurement of the length of roots and fresh weight showed that the ThNAC7 transformed plants displayed significantly improved tolerance to NaCl and Mannitol compared with WT under NaCl and Mannitol. Additionally, SOD and POD activity, and chlorophyll content in OE2, OE5 were significantly higher than WT, but MDA content in OE2 and 5 lines were significantly lower than WT when exposed to 100 mM NaCl, furter suggested that ThNAC7 could confer stress tolerance to transgenic plants.
In order to build a method that could identify the stress tolerance of genes quikly, a transient genetic transformation was established with the whole tobacco (Nicotiana tabacum L.) seedlings as explants. Effects of A. tumefaciens concentration, acetosyringone concentration, Tween20 concentration, sucrose concentration, infection time, and hormone on the transient expression of GUS gene were analysed to determine the optimal transformation condition. A optimal transient genetic transformation condtions were: OD600 value of A. tumefaciens for infiltration 0.2, infiltrating for 3 h, adding 120 μM acetosyringone, 1.5 mg/L KT, 0.5 mg/L NAA, and 3% sucrose to co-culture medium, and co- culture for 3 days|