Galactinol may act as a sugar signal that affects the ethylene signaling pathway and enhances cold tolerance in germinating seeds and young seedlings of tomato.

The cDNA of AtPLDα (Arabidopsis thaliana Phospholipase Dα) gene was introduced into P. tomentosa (Populus tomentosa) under the control of the Cauliflower mosaic virus 35S promoter. Southern and Northern blot analyses suggested that the AtPLDα gene has been transferred into the P. tomentosa genome. No obvious morphological or developmental difference was observed between the transgenic and wild-type (WT) plants. Drought and salt tolerance and gene expression of seedlings of several transgenic lines and WT plants (control) were studied. The results showed that the rhizogenesis rate and the average root-length of transgenic lines were significantly higher than WT plants after mannitol and NaCl treatment under the same growth conditions. Northern blot analysis indicated that the higher the PLDα expression in the transgenic plants, the more tolerant the transgenic plants are to drought and salt treatment. Meanwhile, another group of these transgenic lines and WT plants (control) were treated with PEG 6000 and NaCl separately. The contents of chlorophylls and the activities of some antioxidant enzymes (superoxide dismutase, guaiacol peroxidase and catalase) as well as malondialdehyde and relative electrical conductivity were analyzed. Altogether, our results demonstrated that overexpression of the PLDα gene can enhance the drought and salt tolerance in transgenic P. tomentosa plants.