Bioenergetics of the secondary metabolites production in photosynthetic glandular trichomes

Several commercially important secondary metabolites are produced and accumulated in high amounts by glandular trichomes (GTs), giving the prospect of exploiting trichomes as metabolic cell factories. Due to extremely high metabolic fluxes through GT particular attention was drawn to how they are achieved. The question regarding bioenergetics of these dedicated structures becomes more interesting when one realizes that some cells are photosynthetically active. Despite recent advances, how primary metabolism contributes to GTs high metabolic fluxes is still not fully elucidated. We provide the first reconstruction of specialised metabolism in photosynthetic glandular trichomes of Solanum lycopersicum . With increasing light intensities our model shows a shift of carbon partitioning from catabolic to anabolic reactions driven by the energy availability of the cell. Moreover, we show the benefit of using MEV or MEP pathways under different light conditions. Lastly, we can observe the refixation of the CO2 by RuBisCO in high light conditions. The outcomes of this research close an important gap in knowledge of the role of chloroplast in the synthesis of specialised metabolites in plants’ GTs. ### Competing Interest Statement The authors have declared no competing interest. * CBB : Calvin-Benson-Bassham cycle DMAPP : dimethylallyl diphosphate FBA : flux-balance analysis F6P : Fructose-6-Phosphate GEM : genome-scale metabolic models GT : glandular trichome IPP : isopentenyl diphosphate LP : linear programming MEP : methyl-erythritolphosphate pathwy MEV : mevalonate pathway PETC : photosynthetic electron transfer chain TCA : citric acid cycle.