Combined transcript, proteome, and metabolite analysis of transgenic maize seeds engineered for enhanced carotenoid synthesis reveals pleotropic effects in core metabolism
Fruit-specific downregulation of the DE-ETIOLATED1 (DET1) gene product results in tomato fruits (Solanum lycopersicum) containing enhanced nutritional antioxidants, with no detrimental effects on yield. In an attempt to further our understanding of how modulation of this gene leads to improved quality traits, detailed targeted and multilevel omic characterization has been performed. Metabolite profiling revealed quantitative increases in carotenoid, tocopherol, phenylpropanoids, flavonoids, and anthocyanidins. Qualitative differences could also be identified within the phenolics, including unique formation in fruit pericarp tissues. These changes resulted in increased total antioxidant content both in the polar and nonpolar fractions. Increased transcription of key biosynthetic genes is a likely mechanism producing elevated phenolic-based metabolites. By contrast, high levels of isoprenoids do not appear to result from transcriptional regulation but are more likely related to plastid-based parameters, such as increased plastid volume per cell. Parallel metabolomic and transcriptomic analyses reveal the widespread effects of DET1 downregulation on diverse sectors of metabolism and sites of synthesis. Correlation analysis of transcripts and metabolites independently indicated strong coresponses within and between related pathways/processes. Interestingly, despite the fact that secondary metabolites were the most severely affected in ripe tomato fruit, our integrative analyses suggest that the coordinated activation of core metabolic processes in cell types amenable to plastid biogenesis is the main effect of DET1 loss of function.