NAC transcription factor expression, amino acid concentration and growth of elite rice cultivars upon salt stress

NAC transcription factors (TF) play important roles in regulating osmotic stress tolerance in plants. We tested the expression of 57 NAC genes in the presence of NaCl in young leaves of two elite rice cultivars, Cotaxtla and Tres Rios, which display contrasting responses to salinity at the biochemical and physiological levels. Using qRT-PCR, the expression of 41 out of 57 NAC genes was validated, of which 23 showed regulation by NaCl. We identified two NAC genes (Os02g56600 and Os12g07790) induced in Cotaxtla, but repressed in Tres Rios when plants were exposed to 100 mM NaCl in nutrient solution. In both elite cultivars, treated plants showed higher concentrations of total amino acids and proline in comparison to the controls; in all cases, Cotaxtla plants accumulated more free amino acids and proline than Tres Rios plants. Furthermore, shoot growth was more affected in both cultivars, while root length was not reduced in treated plants in comparison to the controls. We conclude that both elite rice cultivars exhibit different expression patterns of NAC transcription factors as well as biochemical and physiological responses to salt stress, giving rise to better performance of Cotaxtla plants in comparison to Tres Rios plants under our experimental conditions.