GENOME-SCALE METABOLIC NETWORK OF CARBON ASSIMILATION IN A DEVELOPING STEM OF CASSAVA

Cassava is a promising staple crop to enable global food security in the 21st century. Cassava plants produce underground starchy roots, whose yield is depending upon the amount of carbons traded from the aboveground development. Plant stem is a major aboveground sink organ, and its development crucially affects growth of plants, especially during the early age. However, overwhelming carbons to stem growth limits carbon supply for storage root formation. While carbon portioning and utilization for stem development is vitally affecting root yield of cassava plants, the in-depth study of the related metabolism is almost none. Accordingly, this study aimed to investigate the carbon assimilation pathway towards stem biomass synthesis through the genome-scale metabolic network (GSMN) reconstruction. The GSMN pathway, namely stMeRecon (stem-Manihot esculenta Metabolic Pathway Reconstruction), was reconstructed from the integral knowledge of genome information and the formerly defined metabolic pathways of cassava. The resulting pathway was consisted of 924 enzymatic protein coding genes functioning in eight sub-metabolic pathways, involving in 576 metabolic reactions and 459 metabolites. The stMeRecon, finally, describes conversion of sucrose as carbon substrate to synthesize the major components of stem biomass, including carbohydrates (starch and sugars), fibers (cellulose, hemicellulose, and lignin), proteins, and lipids. This study provides the initiative metabolic network model of cassava stem development that would extend understanding of carbon metabolism in developing stem. Furthermore, stMeRecon offers the fundamental data for metabolic modeling of carbon assimilation and, ultimately, shoot-to-root carbon allocation, which is a key factor shaping cassava root yield.