Graduate Student University of Florida Gainesville, Florida
Body of Abstract: Aldoximes are amino acid derivatives and precursors of various specialized metabolites, such as auxins and defense compound cyanogenic glycosides. Moreover, aldoxime accumulation limits the phenylpropanoid biosynthesis pathway in Brassicales. For example, the accumulation of tryptophan-derived aldoxime indole-3-acetaldoxime (IAOx) or its derivatives represses phenylpropanoid production in Arabidopsis and Camelina sativa. Similarly, overproduction of phenylalanine-derived aldoxime phenylacetaldoxime (PAOx) decreases phenylpropanoids. Phenylpropanoids are specialized metabolites mainly derived from phenylalanine through the phenylpropanoid pathway, which generates a wide range of metabolites, including flavonoids and lignin monomers. One mechanism underlying this repression is the accelerated degradation of phenylalanine ammonia-lyase (PAL). As PAL functions at the entry point of the phenylpropanoid pathway, the impact of aldoxime metabolism on phenylpropanoid production is detrimental. It is thought that this metabolic link may contribute to defense-growth tradeoff. Despite the significance of aldoxime metabolism on phenylpropanoid production, the aldoxime-mediated phenylpropanoid repression beyond Brassicales remains unknown. This study aimed to determine the impact of aldoximes on the phenylpropanoid pathway in tomato. Tomato (Solanum lycopersicum) is commonly used as a model system for fruit development and chemistry research in Solanaceae, which includes numerous economically and nutritionally significant cultivated plant species. We generated tomato transgenic lines producing IAOx upon application of a steroid inducer, dexamethasone, to test whether the aldoxime-mediated phenylpropanoid repression is conserved in tomato. Tomato plants with increased IAOx substantially decreased the majority of phenylpropanoids. The transverse section of tomato hypocotyls revealed reduced lignin under the high IAOx condition, suggesting that the accumulation of IAOx represses phenylpropanoids in tomato. Our RNA-seq analysis and untargeted metabolite profiling identified dynamic metabolic and transcriptional changes upon IAOx production.