Journal of Plant Process and Function

Low temperature stress are the most important environmental stresses that limit the growth and yield of tomato plants. In this study, two tomato varieties, Peto Meck and CaljN3 were exposed to cold stress (8 ^oC) after four weeks of growth and sampled at five times of 2, 5, 24, 72, 144 hours after treatments. The expression of transcription factors SlNAC1 and CBF1 with Real-Time qRT-PCR method as well as the Fv/Fm index, soluble and insoluble sugar content and electrolyte leakage index were measured. Soluble and insoluble sugar content increased and decreased respectively under cold stress in the CaljN3, while no significant change was recorded in the Peto Meck. Also the Fv/Fm index decreased in both cultivars. Real time PCR data analysis results showed that gene expression SlNAC1 was increased 7.5 and 3.5 times respectively in Peto Meck and CaljN3 varieties in five hours of cold treatment, while CBF1 gene expression increased only in the CaljN3. Also the increase and decrease trend of electrolyte leakage correlated with the rise and fall in transcription factors versions. These results suggest that change of genes expression including transcription factors SlNAC1 and CBF1 associated with cold tolerance and the results showed that CaljN3 variety of defense mechanisms better and more efficient than the Peto Meck variety and therefore are more tolerant to cold stress.