Chilling tolerance in three tomato transgenic lines overexpressing CBF3 gene controlled by a stress inducible promoter.

Plants integrate and monitor low temperature signals to cope with the continual variations in their environment. Arabidopsis thaliana cold responsive-element binding factor 3 (AtCBF3) plays its role in various cellular activities by modulating multiple genes induced under chilling stress. In this work, AtCBF3 transcription was remarkably induced following chilling stress. AtCBF3-overexpressors namely AtCBF3-Rio Grande, AtCBF3-Moneymaker, and AtCBF3-Roma showed defensible response to various levels of chilling stress, while their isogenic wild type plants indicated hypersensitive response to chilling stress. Detailed photosynthetic studies revealed that AtCBF3 gene has harmonious influences on the expression of a large set of genes by virtue of improved stomatal conductance, transpiration rate, intercellular CO2 concentration, and photosynthetic rate compared to wild type plants. The AtCBF3 lines limited the water status-mediated hypersensitive response by lowering leaf osmotic potential due to overexpression of AtCBF3 under chilling stress. Biochemical analyses followed by phenotypic studies demonstrated that AtCBF3 plants exhibited membrane stability and lush green appearance by limiting membrane ions leakage and malondialdehyde contents and by accumulating more proline, soluble sugars, chlorophyll contents, carotenoid contents, and antioxidant enzymes relative to wild type plants. Hence, with a several lines of evidence, these findings support that tomato transgenic plants overexpressing Arabidopsis CBF3 show enhanced chilling tolerance.