Interaction between light, hormonal and nitric oxide signaling during plastidial biogenesis and differentiation and nutraceutical compounds accumulation in tomato fruits

Abstract

Increases in food nutritional quality has became an important goal of modern programs of genetic improvement of plants and, in this context, tomato is increasingly being adopted as a model species for studies focused on the biosynthesis and accumulation of nutritional/nutraceutical compounds in fresh fruits. Relatively recent evidences have indicated that the levels of carotenoids, flavonoids, phenylflavonoids and vitamins can be simultaneously improved in tomato by changes in light and hormonal perception and transduction, resulting in modifications in both biosynthesis and storage capacity of these compounds, which, in many cases, are associated with alterations in the abundance, size and ultrastructure of plastids (chloroplasts and chromoplasts). Besides light and phytohormones, recent studies have also suggested a possible role for the free radical nitric oxide (NO) in the regulation of these physiological responses. Considering the lack of knowledge on the mechanistic interactions between light, hormones and NO signaling during the control of these responses, the present project aims to analyze, in a integrative way, the influence of four hormonal classes (auxins, cytokinins, abscisic acid and ethylene), NO and light signaling on plastidial biogenesis and differentiation, as well as the accumulation of nutraceutical compounds in tomato fruits. Firstly, the temporal and spatial patterns of hormonal and NO signaling during chloroplast biogenesis and development in immature fruits of tomato photomorphogenic mutants will be characterized. Then, the influence of the hormonal and NO signaling on the chloroplast-to-chromoplast conversion in fruits of photomorphogenic mutants exposed to different light treatments will also be investigated. Finally, the effects of silencing phytochrome A, B1 and B2 genes, specifically in the fruit tissues, on the plastidial development and on the accumulation of nutraceutical compounds will also be analyzed. In all cases, the impacts of light signaling on the hormonal profile and on the NO metabolism will be analyzed in parallel to the characterization of the light influence on the plastidial abundance and ultrastructure, metabolic profile (organic acids, sugars, aminoacids), nutraceutical compound profile (carotenoids, flavonoids, vitamins C and E), as well as in terms of transcriptional profile of key enzymes in the biosynthesis of these high nutritional quality compounds. Taken together, the approaches selected for this project not only have the potential to increase the current knowledge about the involvement of light, phytohormones and NO on the control of plastidial biogenesis and nutritional/nutraceutical quality of tomato fruits, but also have the potential to increase the understanding about the complex crosstalk between plant hormones, NO and the signal transduction pathways triggered by light stimuli. In addition, these studies can also help to direct future plant breeding programs targeted to improve the levels of health-promoting substances in tomato and other fresh fruits. (AU)