PTC&B Accumulation of Proline in NaCl-treated Callus of Six Tomato (Lycopersicon esculentum Mill.) Cultivars

The synthesis, accumulation and degradation of proline are highly regulated by environmental stresses such as salt, drought and metals. This phenomenon has been documented in many plants (Aspinall and Paleg 1981, Kavi-Kishor et al. 2005). In response to stress conditions plants increase osmotic potential within their cells by synthesizing and accumulating compatible osmolytes. Proline is considered one of the most common compatible osmolytes (Claussen 2005) which is directly involved with the osmotic adjustment of the plant cell to external salt stress (Rhodes et al. 1986, Rhodes and Handa 1989). The accumulation of free proline has been studied in a number of taxa subjected to hyperosmotic stress conditions for over 45 years. The accumulation of proline under environmental stress conditions depends on the plant species and the stress level (Kavi-Kishor et al. 2005). Proline seems to have diverse roles under osmotic stress, such as stabilization of protein structures against denaturation; it also stabilizes cell membranes by interacting with phospholipids, and subcellular structures thereby protecting cellular functions (Aspinall and Paleg 1981