Transcriptional network controlling antioxidants in tomato fruit

Increased levels of antioxidants such as ascorbic acid (AsA) and phenols in tomato fruit provide health benefits to consumers through a higher intake in the diet. In fact, antioxidants are involved in the prevention of proliferative and degenerative diseases, such as cancer and cardiovascular ones. Although the metabolism of major antioxidants has been characterized in detail, knowledge on regulatory mechanisms of their content in tomatoes remains still elusive. The aim of the work was to identify genetic and molecular mechanisms controlling AsA and phenol accumulation in ripe tomatoes. In order to identify QTLs controlling antioxidant accumulation in tomato fruit we carried out a comparative analysis of Solanum pennellii x S. lycopersicum cv.M82introgression lines (ILs) over three year trials in greenhouse environment. Also, to dissect QTLs in candidate genes we performed a comparative transcriptomic analysis in tomato pericarp, total RNA from the IL12-4, IL7-3, IL10-1 and M82was hybridized on a combimatrix TomatArray 1.0 over two consecutive years. Among ILs, the IL12-4 showed higher AsA accumulation than M82, the IL 7-3 higher AsA and phenols accumulation and the IL 10-1 lower accumulation of AsA. The transcriptomic approach allowed to identify 253 differentially expressed transcripts in the IL12-4, 260 in the IL 7-3 and 239 in the IL 10-1. Based on functional annotation, gene ontology classification and hierarchical clustering, subsets of differentially expressed transcripts were used to develop model networks describing mechanisms controlling accumulation of antioxidant in tomato fruit. The models we identified explain variations in AsA and phenols levels in terms of metabolic flux and alternative pathways, precursor availability, demand for antioxidants, abundance of reactive oxygen species and ethylene signalling. Currently, efforts are focusing on the development of new molecular markers and innovative breeding approach designs are in progress aimed at pyramiding QTLs for nutritional quality in modern cultivars.