Redox and fructan metabolism. Implication for productivity and nutritional value of crops

Improvement of quality and productivity of four cereal crops, namely wheat, rice, maize and sorghum, could have remarkable impact on human nutrition since these crops currently occupy 83% of worldwide cereal production area and 56% of the entire arable lands. Wheat has been always considered a leading source of energy and fiber in human diet with higher protein content than almost all other cereals. Recently it has also received attention as source of other bio-active molecules with positive effects on human health. These molecules include fructans and antioxidants such as ascorbate, glutathione and polyphenols. Fructans are water-soluble sugars widely used as prebiotics. Recently a new propriety has been attributed to fructans, since they have been reported to have antioxidant properties. Wheat fructans are mainly "graminan type" containing both beta-(2,1) and beta;-(2,6) linkages. It is known that fructan level is high in the kernels during the first period of maturation (20-30% of kernel dry weigh before milky phase) while it decreases to 2% of kernel dry weight at the end of kernel dehydration. Here we report a study on fructan and antioxidant metabolism during the maturation of Triticum durum kernels. Kernels from durum wheat cv Neolatino were collected at different phases of maturation (from 7 to 52 DAA). Changes in activities of the enzymes involved in fructan metabolism, antioxidant metabolites as well as antioxidant total power were analyzed. Since fructan metabolism in wheat is not completely known a study aimed to deepen the knowledge on the enzymes involved in fructan biosynthesis and breakdown has also been performed. It is known that the productivity of plants and the nutritional value of their edible parts strongly depend on plant capability to avoid phytopathogen attack. Phytopathogenic fungi and bacteria affect plant growth and produce toxins that are accumulated in colonized tissues. In this thesis we investigated the biochemical alterations on plant metabolism induced by ophiobolins, secondary metabolites produced by some pathogenic fungi (Bipolaris and Aspergillus spp) that mainly attack rice, maize and sorghum. The knowledge of the process activated in plant by ophiobolins could help to highlight how to reinforce specific plant defense mechanisms in order to reduce the loss in crops caused by the infection induced in crop by ophiobolin producing fungi. Particular attention has been paid to characterize the ophiobolin A-mediated effects on cell proliferation versus death features in plant cells by using Tobacco Bright Yellow – 2 (TBY-2) cell suspension culture as model system.