Tomato production as well as its cultivation area has doubled in the last 20 years, and is the seventh most cultivated food in the world. From the nutritional point of view, tomatoes are highly appreciated because they are a low-calorie food, and have high minerals, vitamins and antioxidants contents. Among the compounds with beneficial health properties are vitamin C and carotenoids, especially esters of beta-carotene and lycopene. Currently, it is a great challenge to develop a commercial hybrid tomato plant whose fruits are rich in phytochemicals. A new strategy to increase fruit quality is to grow plants under controlled conditions of environmental stress. To date it is known that saline stress can increase the accumulation of carotenoids, vitamin C and phenolic compounds, however the results are still preliminary. The carbon level and the redox state of the plant are the main processes involved in the accumulation of secondary metabolites in fruits, and both are modified by stress conditions. Carotenoids are synthesized in the membranes of almost all types of plastids, mainly chloroplast and chromoplast. Previous researches indicate that tomatoes with more active chloroplasts produce, during the maturation, also more active chromoplasts with greater contents of carotenoids and sugars. The transition from chloroplast to chromoplast is the critical step where the largest synthesis of carotenoids occurs. However, the role of plastids in the carotenoids accumulation under salinity conditions is unknown. Recently, a mutant tomato plant res (restored cell estructure by salinity) has been identified to overexpresses the genes of synthesis and signaling of jasmonic acid. The mutant has higher levels of this hormone in the roots of plants grown under both normal and saline conditions. Surprisingly, the mutant plants when grown under control conditions present morphological changes and chlorotic leaves, whereas in salinity conditions they are able to reorganize the cellular structure and the chlorophyll synthesis. This work aims to determine how a saline stress condition can affect tomato quality and the accumulation of carotenoids, as well as to understand the role of the leaf and fruit plastids and of the jasmonate in this process. Tomatoes from plants submitted to normal conditions and saline stress will be used, using the mutant res and a control cultivar "Moneymaker" (MM), which presents a representative response mechanism to salinity. It is intended to evaluate how the saline stress can affect the chloroplast-chromoplast transition and therefore activate the biosynthesis of carotenoids, as well as the final chromoplast composition in the mature fruit and the role of jasmonate in this process. For this purpose, the accumulation of sugars and reactive oxygen species in tomato leaves and their relation to the accumulation of carotenoids in fruits will be evaluated, also it is proposed to study at the proteomic level which routes or key mechanisms in leaf and fruit plastids can determine the balance between stress and quality in conditions of saline stress.
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