LAUSR

Salinity restricts the growth of trees to varying extents, but the regulatory mechanisms involved in their varying salt tolerance are largely unknown. In efforts to elucidate these mechanisms, we identified a total of 99 genes in the ERF family of transcription factors and examined their expression patterns under salt stress in Populus alba var. pyramidalis. We found that a B4 group gene, PalERF109, was rapidly induced by salt treatment, and preferentially expressed in stems and petioles, where it is probably involved in transport of ions and water in xylem. Overexpression of PalERF109 enhanced the salt tolerance of the poplar, and further analysis showed that it directly up-regulated a high-affinity K+ transporter (HKT) gene, PalHKT1;2. The results clearly indicate that PalERF109 enhances salt tolerance at least partially through direct activation of PalHKT1;2, and extend understanding of ERF genes' roles in trees' stress responses.