Analysis of the diurnal variation of carbohydrates and metabolites of energy-cane and sugarcane

Energy-cane is a commercial hybrid originated from the crossing of commercial sugarcane (high sugar content) and Saccharum spontaneum (high fiber content) plants. The result of this cross resulted in plants with high fiber content, low sucrose content and higher productivity (2,5 times more) compared to commercial sugarcane hybrids, which made energy-cane an ideal plant to produce ethanol from second generation and bioelectricity. In Brazil, some companies have developed commercial varieties of energy-cane, such as GranBio S/A. Although sugarcane is widely studied from a genomic point of view and through molecular biology, very little is known about energy-cane. Here, we analyze carbohydrates and use metabolomics approaches to understand how the profile of carbohydrates and metabolites of the leaves (source organ) and stalk (sink organ) of energy-cane and sugarcane behave during diurnal cycle and how these organs interact metabolically with each other to adapt to the environment and sustain their growth. For this, we carried out an experiment in which the leaf and internodes of sugarcane and energy-cane were collected during a 24-hour diurnal cycle. Then, carbohydrates were extracted and analyzed by HPAEC-PAD. To explore metabolic differences, samples were subjected to LC-MS and GC-MS approaches. The spectra obtained were quantified by MZMine2 and the compounds identified through the GNPS database (Global Natural Product Social Molecular Networking) and as complementary identification we used CANOPUS (SIRIUS v. 4.9.3). As a result, we identified that sugars (sucrose, glucose, fructose) and some metabolites underwent a phase shift during the diurnal variation in leaves and internodes organs and many biological pathways were more active in energy-cane than in sugarcane, such as the phenylpropanoid pathway. Although energy-cane has less sucrose than sugarcane, a higher concentration of starch was observed in the internodes of the energy-cane, suggesting that energy-cane uses this polymer to supply its bioenergetic metabolism. Most of the metabolites identified by CANOPUS during the diurnal cycle were classified as organoheterocyclic compounds, oxygenated organic compounds, organic acids and derivatives, benzeneides, lipids and related molecules and phenylpropanoids. We also show that the greatest metabolic differences between sugarcane and energy-cane occur during the night period. As next steps, we will integrate transcriptomics and metabolomics data through co-expression network analysis. Thus, the knowledge generated about the metabolism of energy-cane compared to sugarcane will enable the development of more productive varieties to supply the bioenergy sector.