A Populus euphratica NAC protein regulating Na⁺/K⁺ homeostasis improves salt tolerance in Arabidopsis thaliana

NAC transcription factors are plant-specific and play an important role in responses to biotic and abiotic stresses. Populus euphratica is a salt-tolerant tree species growing in semi-arid saline areas. A stress responsive gene was successfully isolated from this species and named PeNAC1. The isolated cDNA encoded a protein containing a conserved NAC domain that belonged to the ATAF subgroup of the NAC protein family. The protein was localized to the nucleus and its C-terminus had transcriptional activation activity. Northern hybridization showed that its expression was strongly induced by drought and salt stress, but only slightly induced by ABA treatment in P. euphratica. Transgenic Arabidopsis overexpressing PeNAC1 showed enhanced tolerance to salt stress, with lower Na(+)/K(+) ratios in the roots and leaves, and significantly inhibited expression levels of AtHKT1. Our results suggest that PeNAC1 plays a role in the plant response to salt stress by regulating Na(+)/K(+) homeostasis.