Genotypic changes in protein synthesis in tomato during low and high temperatures and the alleviation of chilling and heat injury by calcium

inconnu. In the present investigation, the differences in callus dry weight, seed germination, protein pattern and isozymes in response to low (10C) and high (40C) temperature were studied in tomato. In addition, the involvement of calcium in avoidance of stress injury was also studied. Callus dry weight and percentage of seed germination were affected by cold and heat stress, and enhanced by calcium treatment. Heat and cold stresses also reduced the synthesis of protein sets while, most of these proteins were recovered by the application of calcium treatment. This recovery of gene expression in conjunction with the enhancement of callus growth and seed germination under cold and heat stresses as a result of calcium treatment may reflect the important role of calcium in the alleviation of stress injury. The results suggested that the injury caused by chilling and heat stress could be alleviated to some extent by treating tomato with 5mM Ca. Low temperature induced the synthesis of 10 new protein bands (71.32-16.64 Kd.). On the other side, 11 newly synthesized heat-shock proteins (101.99 - 16.64 Kd.) were induced under heat stress. The heat-tolerant variety possessed HSP70, HSP60 and two types of sHSPs (26.53 and 18.27 Kd.), whereas the heat-sensitive variety exhibited HSP70 and one type of sHSPs (16.64). The cold-tolerant variety was marked by the expression of 4 newly synthesized protein bands (35.96, 22.53, 22.18 and 16.64 Kd.) under cold stress, as compared with cold-sensitive one. The analysis of isozymes revealed the induction of one malate dehydrogenase band and the reduction of one esterase band as a result of cold treatment. Heat stress was found to affect the expression of isozymes in tomato of which one peroxidase band, one band of malate dehydrogenase and 2 bands of esterase were suppressed. Meanwhile, only one esterase band was induced in the tolerant variety under heat stress. The results also demonstrated that tomato respond to cold and heat stresses with distinct changes in gene expression. These are superimposed on general reduction of callus growth and seed germination that is a consequence of temperature stress. Furthermore, cold and heat stresses lead to differential expression of the genetic information in tomato, resulting in changes in gene products, including protein and isozymes profiles. These stresses induced the synthesis of certain proteins and simultaneously decreased the expression of other protein sets.