Differential metabolic and regulatory responses to exogenous glucose uptake across plant species revealed by isotopic metabolomics
Plants rely on photosynthesis to fix carbon and produce sugars required for growth, energy metabolism, and structural development. The roots can also absorb exogenous sugars from the surrounding soil environment. However, how acquired sugars are metabolized, regulated, and integrated into plant metabolic networks, and how this varies across species, remains poorly understood. Untargeted metabolomic profiling was applied to below-ground and aerial tissues of Arabidopsis thaliana, Solanum lycopersicum cv. Micro-Tom, and Gossypium hirsutum seedlings treated with ¹²C or ¹³C6-glucose (30 mM, 48 h) under continuous illumination to minimize remobilization of endogenous carbon reserves. The ¹²C-metabolomic profiles revealed species-specific responses among the three species examined with 40 significantly altered metabolites in A. thaliana roots (predominantly decreased), 6 in S. lycopersicum roots (predominantly increased), and none in G. hirsutum. All three species transported ¹³C-glucose to aerial tissues, with A. thaliana showing the highest ¹³C enrichment (0.85% dry weight), compared to S. lycopersicum cv. Micro-Tom (0.20%) and G. hirsutum (0.34%). ¹³C-metabolomic profiling across root, hypocotyl, and shoot tissues identified species-specific sets of labeled metabolites in A. thaliana, S. lycopersicum cv. Micro-Tom, and G. hirsutum. Isotopologue distributions and the degree of correlation between tissues likewise differed among the three species, indicating divergent patterns of glucose-derived carbon partitioning. These findings demonstrate that while glucose uptake is conserved among these species, its metabolic impact and utilization are different among different plant species examined.