Class I small heat-shock protein gives thermotolerance in tobacco

We chose a class I cytosolic small HSP gene, TLHS1, whose protein showed a stronger molecular chaperone activity among the class I cytosolic small HSPs in tobacco, and constitutively expressed it in tobacco. Bioassay of the transgenic tobacco seedlings at T2 generation for thermotolerance was performed as the rates of cotyledon opening after heat-stress. Transgenic tobacco seedlings with the constitutively expressed TLHS1 showed up to two times higher cotyledon opening rates compared to the transgenic tobacco seedlings carrying the TLHS1 gene in antisense orientation and the expression vector only after the high temperature stresses of 40 °C and 45 °C for 1 to 4 h. When the correlation between the level of TLHS1 accumulated in the seedling before the heat-stress and the level of thermotolerance was examined, a strong correlation between them could be observed. Together these results support the thermoprotective function of a class I small HSP in plants.