Modeling metabolic fluxes underlying cassava storage root growth through E-Fmin analysis

Cassava (Manihot esculenta Crantz) is a staple crop that has a great impact on global food security. Cassava yield improvement has continuously been researched, resulting in various elite cultivars bred during last decades. To pursue a better yield, it requires deep insight into metabolic process underlying the assimilation and conversion of carbon substrates to storage root biomass. In this study, we employed E-Fmin analysis to model carbon metabolism in storage roots of cassava. The model was constructed based on primary metabolism of carbon assimilation pathway in non-photosynthetic cells and corresponding gene expression data. The model, namely rMeCBMx-EFmin, was able to mimic growth of storage roots measured from Kasetsart 50 (KU50). The rMeCBMx-EFmin highlighted the tentative metabolic flux distribution that carbon substrates were economically converted into cellular biomass of cassava storage roots. The small total flux (3.2749 mmol gDWSRs−1 day−1) with respect to the published model of cassava storage roots (4.4255 mmol gDWSRs−1 day−1) indicated metabolic frugality in the simulated root metabolism. The simulation also showed that alpha-D-glucose-6-phosphate (-D-Glc-6P) partitioned from respiration was a key carbon precursor imported to plastid for storage root biomass production. The knowledge gained would be beneficial for later experimental design of yield enhancement.