Nuclear Magnetic Resonance Characterizes Metabolic Differences in Cymbopogon Schoenanthus Subsp. Proximus Embryogenic and Organogenic Calli and their Regenerated Shoots

NMR-based metabolic profiling of polar extracts of somatic embryogenic and organogenic cultures of the medicinal plant Cymbopogon schoenanthus subsp. proximus were studied. Regeneration through somatic embryogenesis was done on media containing 2,4-D and BAP while organogenesis was achieved on media containing NAA and BAP. Fifty-two metabolites were identified in embryogenic calli (EC), organogenic calli (OC), regenerated embryogenic shoots (ES), and organogenic shoots (OS). Chemometrics and cluster analysis were used to depict the correlation between the groups investigated. Metabolic profiles revealed unique metabolites in ES (serine and lactate) and in OS (2-hydroxyisobutyrate, tyrosine, histamine and homoserine). Quantitative differences as manifested by relative concentrations through heat map and fold change analyses were significant in the following comparisons: calli type, embryogenic tissues, organogenic tissues, and shoot type. In a comparison of calli types, proline, asparagine and arginine were upregulated in EC and sucrose was upregulated in OC. When comparing embryogenic tissues, monosaccharides were upregulated in EC, while proline, pyroglutamate and 4-aminobutyrate were upregulated in ES. Upon comparison of organogenic tissues, trigonelline increased by 17-fold in OS; however, monosaccharides were upregulated in OC. Finally, when comparing shoot types, 4-aminobutyrate, betaine and proline were upregulated in ES, while mono- and disaccharides were upregulated in OS. The embryogenic system was characterized by accumulation of stress related metabolites (proline); however, glycolate was identified only in the organogenesis system. The present work contributes to the understanding of the metabolic characteristics and differences between the two regeneration systems as manifested by profiles of EC, OC, and their regenerated shoots. Metabolic characteristics of two regeneration systems (somatic embryogenesis and organogenesis) of Cymbopogon schoenanthus were examined using NMR-based profiles of calli and their regenerated shoots, revealing clear qualitative and quantitative differences between the two systems at the studied developmental stages.