Potato plants ectopically expressing Arabidopsis thaliana CBF3 exhibit enhanced tolerance to high-temperature stress

CBF3, a known cold-inducible gene that encodes a transcription factor, was isolated from Arabidopsis thaliana and introduced into the potato (Solanum tuberosum cv. luyin NO.1') under the control of the CaMV35S promoter or the rd29A promoter. Our results revealed that temperature of 40 degrees C or higher can significantly induce AtCBF3 expression. After heat stress, the net photosynthetic rate (P-n), the maximal photochemical efficiency of photosystem II (PSII) (F-v/F-m) and the accumulation of the D1 protein were higher in the transgenic lines than in the wild-type (WT) line. Moreover, compared with the WT line, O-2(.-) and H2O2 accumulation in the transgenic lines were reduced. A Q-PCR assay of a subset of the genes involved in photosynthesis and antioxidant defence further verified the above results. Interestingly, under heat stress conditions, the accumulation of heat-shock protein 70 (HSP70) increased in the WT line but decreased in the transgenic lines. These results suggest that potato plants ectopically expressing AtCBF3 exhibited enhanced tolerance to high temperature, which is associated with improved photosynthesis and antioxidant defence via induction of the expression of many stress-inducible genes. However, this mechanism may not depend upon the regulatory pathways in which HSP70 is involved. In this study, we found that transformation of tomato plants with the AtCBF3 gene enhanced tolerance to high temperatures. AtCBF3 improved the capacities of photosynthesis and antioxidant defense by regulating the expression of genes involved in these functions, and this enhanced tolerance might not depend on the regulatory pathways in which HSP70 is involved. The expression of AtCBF3 was induced by high temperature possibly through the regulatory pathways that Ca2+ participates in.