Overexpression of the Heat Shock-Specific Transcription Factor HSFA1D Enhances Thermotolerance in Tobacco Plants

Among different abiotic stresses, heat stress has the most devastating impact on plant growth. Heat shock transcription factors are known to play an important role in regulating heat stress in plants. Tobacco (Nicotiana benthamiana) was transformed with heat shock transcription factor HsfA1d by transfecting leaf discs with Agrobacterium strain GV3101 carrying CaMV35S-YFP:: HsfA1d construct. After PCR and confocal-based confirmation, HsfA1d overexpression lines (OX1, OX2 and OX3) were evaluated for their response to heat stress. Overexpression lines on average showed 33.26% less electrolyte leakage after induction of heat stress at 42°C compared to wild type plants (WT). No significant decrease was recorded in the chlorophyll content of overexpression lines whereas significant decrease was recorded in the chlorophyll content of WT plants following heat stress. Similarly, no significant reduction in the water content of the leaves of overexpression lines was recorded compared to 33.87% reduction in leaf water content of WT plants as a result of heat stress. Furthermore, overexpression lines accumulated significantly higher amounts of proline compared to WT, both at room temperature and at 42°C. The above results showed that HsfA1d positively regulates thermotolerance in tobacco plants and can be used as target gene for engineering thermotolerance in crops.