Abstract
The stress resistance of plants can be enhanced by regulating the expression of multiple downstream genes associated with stress resistance. We used the Agrobacterium method to transfer the tomato jasmonic ethylene responsive factors (JERFs) gene that encodes the ethylene response factor (ERF) like transcription factor to the genome of a hybrid poplar (Populus alba x Populus berolinensis). Eighteen resistant plants were obtained, of which 13 were identified by polymerase chain reaction (PCR), reverse transcriptase PCR and Southern blot analyses as having incorporated the JERFs gene and able to express it at the transcriptional level. Salinity tests were conducted in a greenhouse with 0, 100, 200 and 300 mM NaCl. In the absence of NaCl, the transgenic plants were significantly taller than the control plants, but no statistically significant differences in the concentrations of proline and chlorophyll were observed. With increasing salinity, the extent of damage was significantly less in transgenic plants than that in control plants, and the reductions in height, basal diameter and biomass were less in transgenic plants than those in control plants. At 200 and 300 mM NaCl concentrations, transgenic plants were 128.9% and 98.8% taller, respectively, and had 199.8% and 113.0% more dry biomass, respectively, than control plants. The saline-induced reduction in leaf water content and increase in root/crown ratio were less in transgenic plants than in control plants. Foliar proline concentration increased more in response to salt treatment in transgenic plants than in control plants. Foliar Na(+) concentration was higher in transgenic plants than in control plants. In the coastal area in Panjin of Liaoning where the total soil salt concentration is 0.3%, a salt tolerance trial of transgenic plants indicated that 3-year-old transgenic plants were 14.5% and 33.6% taller than the control plants at two field sites. The transgenic plants at the two field sites were growing vigorously, had dark green leaves and showed no symptoms of salt damage, implying that the JERFs gene enhanced their salt tolerance.