Functional characterization of transgenic lines of the grass Setaria viridis silenced for laccases potentially involved in lignification

• Grant number: 24/22301-7
• Support Opportunities: Scholarships in Brazil - Master
• Start date: June 01, 2025
• End date: December 31, 2026
• Field of knowledge: Biological Sciences - Botany - Pant Physiology
• Principal Investigator: Igor Cesarino
• Grantee: Arthur Netto Escudeiro
• Host Institution: Instituto de Biociências (IB). Universidade de São Paulo (USP). São Paulo , SP, Brazil
• Associated research grant: 21/06142-8 - Steering the shikimate/phenylpropanoid pathway: from gene function discovery to green factories, AP.BIOEN.JP2

Abstract

The structure and composition of the plant cell wall are major factors that hinder the production of biofuels and biomaterials from plant biomass. Therefore, it is essential to understand the mechanisms that control cell wall structure and how these aspects affect the release of monosaccharides during the enzymatic hydrolysis of wall polysaccharides, a fact known as biomass recalcitrance. Lignin is a cell wall polymer that limits the access of hydrolytic enzymes to their substrates in the wall, and is considered the main factor responsible for biomass recalcitrance. Therefore, it is essential to understand lignin metabolism, especially in C4 grasses, which have a great capacity to accumulate biomass. Laccases are a group of enzymes that participate in the lignification process by oxidizing monolignols, generating radicals that cross-couple to form the lignin polymer. However, the study of laccases is still limited, with little genetic evidence of their involvement in lignin polymerization in grasses. In previous studies, our laboratory identified laccases potentially involved in lignin metabolism in the model grass Setaria viridis, leading to the generation of transgenic lines silenced for the target genes, co-orthologs of the AtLAC4 and AtLAC17 genes of Arabidopsis thaliana, whose involvement in lignin polymerization was validated by reverse genetics. Thus, this project proposes the phenotypic characterization of these lines through i) analysis of biomass accumulation; ii) histochemical assays for the localization of lignin and tricin in situ; iii) determination of lignin content and composition and profiling of structural polysaccharides; and iv) analysis of saccharification potential. The characterization of these laccases will not only fill a knowledge gap in lignin deposition in C4 grasses, but will also validate potential biotechnological strategies for the bioeconomy. (AU)