Impact of successive short starvations of nitrogen nutrition on plant fitness and polyphenol metabolism of tomato

Polyphenols are plant secondary metabolites widely distributed in the plant kingdom. They display a large variety of activities and are notably involved in plant defense against pathogens. These molecules are also implicated in fruits and vegetables quali ty, by contributing to colour and taste and by showing in vitro antioxidant and anticarcinogenic effects assumed to participate to the health value of food. A strong international interest relies in an optimization of polyphenols contents in marketable pl ants in order to (i) increase food quality (aspect, taste and nutritional value) and to (ii) enhance natural plant defense that lower the use of chemicals for crop protection. The fact that polyphenols are strongly influenced by the plant environment impl ies that modulating plant growth conditions could be an "easy way" to enhance their content in plant. Previous research conducted by the Norwegian and the French partners indicate that low nitrogen availability increases polyphenol content in tomato leave s and fruits. As nitrogen is essential for plant growth, new crop methods regarding nitrogen fertilization should be developed to enable high polyphenolic content and sustain growth of the plant. The objective of the project is to determine the impact of short but successive nitrogen starvations on plant growth and polyphenols accumulation in leaves and fruits of tomato. The complementary skills developed by the two partners (from ecopysiology to molecular biology) will enable a very integrative study enc ompassing plant growth analyses and polyphenols biosynthetic pathway activity (enzymatic activities, gene expression of key genes). This project truly addresses questions of general interest for basic research regarding plant growth regulation and regula tion of metabolic pathway by environmental factors, and also short-term applied research by addressing important issues for greenhouse crop producers such as plant defense, product quality and yield optimization.