Molecular cloning and expression analysis of 13 NAC transcription factors in Miscanthus lutarioriparius

The 13 MlNAC genes could respond to various abiotic stresses, suggesting their crucial roles in stress response. Overexpression of MlNAC2 in Arabidopsis led to improved drought tolerance. NAC (NAM, ATAF1/2 and CUC2) proteins are plant-specific transcription factors that play crucial roles in plant development, growth and stress responses. In this study, 13 stress-responsive NAC genes were identified from Miscanthus lutarioriparius. Full-length cDNA sequences were obtained for 11 MlNAC genes, which were phylogenetically classified into six subfamilies. Sequence alignment revealed the highly conserved NAC domain in the N-terminus of these MlNACs, while the C-terminus was highly divergent. We performed quantitative real-time RT-PCR to examine the expression profiles of MlNAC genes in different tissues including root, rhizome, mature stem, young stem, leaf and sheath. The 13 MlNAC genes displayed distinct tissue-specific patterns in six tissues examined. To gain further insight into their roles in response to abiotic stresses, expressions of MlNAC genes were analyzed under different stresses and hormone treatments including salt, drought, cold, wounding, abscisic acid, Methyl jasmonate and salicylic acid. The 13 MlNAC genes could respond to at least five stress treatments, and over 100-fold variations in transcript levels of MlNAC1, MlNAC2, MlNAC4, and MlNAC12 were observed in salt, drought and MeJA treatments, which indicated that MlNACs play crucial roles in stress response. Crosstalk among various abiotic stress and hormone responses was also discussed based on the expression of MlNAC genes. Overexpression of MlNAC2 in Arabidopsis (Col-0) led to improved drought tolerance. The water loss rate was significantly lower, and the recovery rate after a 60-min dehydration stress treatment was significantly higher in the MlNAC2 overexpression lines than the control.