Non GMO fruit factories: Strategies for modulating metabolic pathways in the tomato fruit

Abstract Multiple structural and regulatory genes modulate biosynthetic pathways, such as those leading to the accumulation and profile of sugars and carotenoids in the mature tomato fruit. Natural genetic variation among wild relatives of the cultivated tomato provides an important, non-genetically modified organisms (non-GMO), resource for improving both horticultural and fruit quality traits of elite tomato varieties. Unfortunately, this natural resource is under-exploited in plant breeding. In this presentation, we uncover yet another level in the potential of utilizing such strategy, focusing primarily on gene interactions. With the advances made in recent years in the high throughput molecular characterization and analysis technologies, it is now possible to detect simultaneous effects of multiple genes. Among the technologies available for such comprehensive analysis is the constantly evolving gene databases and analytical technologies referred to as genomics, proteomics, and metabolomics. A comprehensive functional linkage-map of structural genes known to encode enzymes of the carbohydrate metabolic pathway in the tomato fruit was constructed. This functional map aided the discovery of two interacting chromosomal regions, introgressed from the wild L. hirsutum , leading to almost three-fold epistatic increase in fructose to glucose ratio (FGR) in the mature tomato fruit. Such a substantial interaction effect could not have been otherwise discovered, because one of these loci presents a small, inconsistent additive effect on the fruit sugar profile. A similar strategy was applied to uncover regulatory genes leading to a major increase in lycopene concentration, and to the modulation of carotenoid profile in the ripe tomato fruit. A functional linkage-map of light regulated genes has been constructed. The analysis of interaction effects between these genes and high pigment mutations resulted in up to three-fold increase in lycopene concentration and a shift towards the production of valuable colorless carotenoids. Our studies demonstrate that a substantial modulation of fruit biosynthetic pathways can be obtained by non-GMO technologies. Such modulation can either increase metabolite levels or alter fruit metabolic architecture, significantly beyond the currently known standards. The strategy presented can also be exploited to engineer metabolic pathways in species other than the tomato.