Overexpression of chloroplast-localized small molecular heat-shock protein enhances chilling tolerance in tomato plant.

There are many reports about the correlation between small molecular heat-shock protein (sHSP) and the acquirement of chilling tolerance, but no direct evidence that sHSP confers enhanced chilling tolerance to plant has been reported. A DNA construct, including tomato chloroplast-localized small molecular heat-shock protein (CPsHSP) cDNA under the control of cauliflower mosaic virus 35S (35SCaMV) promoter, was introduced into the genome of tomato plants. The chilling tolerance of the transgenic tomato lines and the non-transgenic tomato was evaluated. After exposure to chilling stress, the transgenic plants exhibited lighter chilling-injured symptoms, suffered less electrolyte leakage and less destruction of chlorophyll, accumulated less anthocyanins and less MDA and kept higher value of net photosynthetic rate, than non-transgenic plant. All results indicated consistently that transgenic tomato plants had stronger chilling tolerance. These characters are ascribed to constitutive expression of cpshsp and lead to the conclusion that HSP can enhance chilling tolerance in plant.