Molecular analysis of two salt-responsive NAC-family genes and their expression analysis in tomato

The NAC family transcription factor has demonstrated its importance in plant development and environmental stress response. Based on the microarray results under salt stress and EST information, the full-length cDNAs of two salt-inducible NAC-family genes (SlNAC1, SlNAM1) were isolated from a salt tolerant tomato cultivar, Edkawi, using Rapid Amplification of cDNA Ends (RACE). SlNAC1 and SlNAM1 encoded 301 and 296 amino acids, respectively, and the deduced protein sequences contained the typical domain of NAC-family transcription factors. Tissue expression profile analysis using semi-quantitative RT-PCR showed that SlNAC1 was expressed mainly in root, flower and green fruit; transcripts of SlNAM1 were detected in all tested tissues except for root, and high-level expression was detected in flower and matured tomato fruit. Both SlNAC1 and SlNAM1 were induced by salt stress in Edkawi, while the expression pattern was different in a salt-sensitive cultivar, ZS-5. Phylogenetic analysis for putative NAC-family peptides available in the tomato genome indicated a wide diversity of this gene family. Results obtained in the present study suggest that both SlNAC1 and SlNAM1 might play important roles in tomato stress tolerance.