Abstract
Recently, we published a set of tobacco lines expressing the Daucus carota (carrot) DcLCYB1 gene with accelerated development, increased carotenoid content, photosynthetic efficiency, and yield. Because of this development, DcLCYB1 expression might be of general interest in crop species as a strategy to accelerate development and increase biomass production under field conditions. However, to follow this path, a better understanding of the molecular basis of this phenotype is essential. Here, we combine OMICs (RNAseq, proteomics, and metabolomics) approaches to advance our understanding of the broader effect of LCYB expression on the tobacco transcriptome and metabolism. Upon DcLCYB1 expression, the tobacco transcriptome (~2,000 genes), proteome (~700 proteins), and metabolome (26 metabolites) showed a high number of changes in the genes involved in metabolic processes related to cell wall, lipids, glycolysis, and secondary metabolism. Gene and protein networks revealed clusters of interacting genes and proteins mainly involved in ribosome and RNA metabolism and translation. In addition, abiotic stress-related genes and proteins were mainly upregulated in the transgenic lines. This was well in line with an enhanced stress (high light, salt, and H2O2) tolerance response in all the transgenic lines compared with the wild type. Altogether, our results show an extended and coordinated response beyond the chloroplast (nucleus and cytosol) at the transcriptome, proteome, and metabolome levels, supporting enhanced plant growth under normal and stress conditions. This final evidence completes the set of benefits conferred by the expression of the DcLCYB1 gene, making it a very promising bioengineering tool to generate super crops.
Highlights
Carotenoids are C40 isoprenoid compounds synthesized in the plastids of photosynthetic and some nonphotosynthetic organisms (Ruiz-Sola and Rodriguez-Concepcion, 2012)
In tobacco, carrot, and sweet potato LCYB-expressing lines, a carotenoid increase was accompanied by an induction in carotenoid genes such as phytoene synthase (PSY), phytoene desaturase (PDS), ζ-carotene desaturase (ZDS), zeaxanthin epoxidase (ZEP), violaxanthin deepoxidase (VDE), and neoxanthin synthase (NXS) (Moreno et al, 2013; Shi et al, 2015; Kang et al, 2018); this suggests the possibility that an additional signal coordinates the expression of carotenoid genes
Tobacco (Nicotiana tabacum cultivar Xanthi NN) wild type and transgenic lines were raised from seeds germinated in Petri dishes containing an MS medium supplemented with 30 g/L sucrose (Murashige and Skoog, 1962) and kanamycin (100 mg/mL)
Summary
Carotenoids are C40 isoprenoid compounds synthesized in the plastids of photosynthetic and some nonphotosynthetic organisms (e.g., plants, algae, fungi, and bacteria) (Ruiz-Sola and Rodriguez-Concepcion, 2012). Carotenoids (e.g., βcarotene) have been shown to have antioxidant-promoting activities in humans (Fraser and Bramley, 2004; Rao and Rao, 2007). These properties make β-carotene a very valuable molecule for plant functioning, and for improving food quality content in crops. (over)expression of the LCYB gene in Arabidopsis, tomato, and sweet potato leads to increased tolerance to abiotic stresses, such as salt and drought (D’Ambrosio et al, 2004; Chen et al, 2011; Kang et al, 2018). Tomato ripening inhibitor (RIN) regulates carotenoid accumulation via binding to the promoter region of the PSY gene (Martel et al, 2011). A kiwi R2R3 MYB (AdMYB7) that binds to and activates the expression of LCYB (and chlorophyll biosynthetic genes) is responsible for chlorophyll and carotenoid accumulation in kiwi (Ampomah-Dwamena et al, 2019)
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