Rechanneling Carbon Flow with Potential to Increase Valuable Biomass Feedstocks

Different aspects of plant biomass make it an important feedstock for fuel production, providing a promising solution to the sustainable energy challenge in the 21^st century. We hypothesize that manipulation of carbon flow could positively impact plant biomass and therefore used the artificial microRNA (amiR) strategy to silence the NADP-malic enzyme family in Arabidopsis thaliana. Compared with wild-type plants, the amiR plants showed 16.4% (SE±2.1) increase in daily net CO₂ fixation rate with concomitant increase in dry biomass (22.1%, SE±4.4) while maintaining comparable rates of instantaneous water-use efficiency (WUE) under similar photosynthetically active radiation (PAR, 150 μmol m^-2 s^-1). Diel metabolomics and proteomics analyses revealed significant changes in at least 27 metabolites and 830 proteins between amiRs and wild-type lines, allowing us to assess the carbon movement from accumulated malic acid into sugars, carbohydrates, lipids, etc. Furthermore, the dry biomass recalcitrance of the amiR plants was reduced when compared with wild-type plants, resulting in 24% (SE±3.3) more sugar release from transgenic cell wall after mild pretreatment. Taken together, this research demonstrated that managing carbon flow within plant metabolism could improve different aspects of biomass feedstocks advancing the current capabilities of plants for fiber and fuels production.