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Biotechnological strategies for genetic improvement of grasses for biofuel production


Biomass conversion is currently the most economically viable strategy for the production of liquid biofuels, as is the case with cellulosic ethanol. The complex network of polymers present in the cell wall of plant biomass decreases the fermentation of free sugars by yeasts and is a major bottleneck for biofuel production. In this context, the genetic modification of the plant cell wall represents a powerful tool to reduce biomass recalcitrance, increasing the viability of the biofuel production process. Here, we intend to compare three different strategies for cell wall modification, with the aim of decreasing recalcitrance and consequently increasing biomass digestibility. For these studies, it will be used the grass model plant Setaria viridis, a species phylogenetically related to sugarcane, a crop that is broadly used for ethanol production. Using CRISPR/Cas9 technology, the COMT and BAHD genes, responsible for the incorporation of lignin and ferulate into the cell wall, respectively, will be edited. In addition, the gene XAT, responsible for the incorporation of arabinose residues in the side chains of the hemicellulosic fraction of the cell wall, will be overexpressed. After genetic modification, the cell wall and the biomass of the modified plants will be characterized in detail, to verify the mechanisms by which genetic modifications increase biomass digestibility. These results will help to further design a rational strategy for the development of genetically modified sugarcane with increased potential for bioethanol production. In this project, it is also intended to establish a protocol for the genetic editing of Setaria viridis through the production of CRISPR/Cas9 ribonucleoproteins, generating non-transgenic plants, in order to apply this technique in sugarcane in the future. (AU)