Proline Effect on Shoot Organogenesis and Protein Synthesis in Salinity-Stressed Tomato Cultures

Efficient de novo shoot organogenesis from hypocotyls and cotyledons of tomato (Lycopersicon esculentum Mill.) was affected by sodium chloride and proline. Sodium chloride at 100 and 150 mM inhibited the shoot regeneration. The fresh and dry weights were also reduced. Addition of proline (100 mg/L) to the medium containing NaCI counteracted the inhibitory effect of NaCI and enhanced shoot regeneration, especially at high NaCI levels.
SDS-PAGE analyses of extracted proteins, revealed that in cultures grown in medium with proline, extra polypeptides of Mr. (Molecular weight) 190, 58, 45 and 26 kDaa (Kilodaltons) accumulated. These polypeptides were not present in control cultures, but also accumulated at 25 mM NaCI. As NaCI was increased in the medium a new protein of Mr. 67 kDaa also accumulated. Proteins of Mr. 67, 52-45 and 62 kDaa were also accumulated when proline was added to the saline medium. Proline directly or indirectly play an important role in protein accumulation and in cell adaptation to salinity stress.