Enhanced stress tolerance in transgenic pine expressing the pepper CaPF1 gene is associated with the polyamine biosynthesis

ERF/AP2 transcription factors play an important role in plant stress tolerance. However, little is known about the functional significance of ERF/AP2 genes in pine, compared to the model plant species Arabidopsis. Capsicum annuum pathogen and freezing tolerance-related protein 1 (CaPF1) is an ERF/AP2 transcription factor. We show here that overexpression of CaPF1 resulted in a dramatic increase in tolerance to drought, freezing, and salt stress in a gymnosperm species, eastern white pine (Pinus strobus L.). Measurement of polyamines demonstrated that the levels of putrescine (Put), spermidine (Spd), and spermine (Spm) did not increase but remain constant in CaPF1-overexpressed eastern white pine, whereas the levels decreased in the controls, probably increasing the ability of transgenic callus cultures and plants to stress tolerance. These results demonstrated that enhanced stress tolerance in transgenic pine expressing the pepper CaPF1 gene is associated with the polyamine biosynthesis and this pepper transcription factor may be used to engineer pine species for multiple stress tolerance.