Flavone Synthases in Setaria viridis: tricin biosynthesis and lignification

• Grant number: 24/07176-1
• Support Opportunities: Scholarships in Brazil - Doctorate (Direct)
• Start date: August 01, 2024
• End date: July 31, 2028
• Field of knowledge: Biological Sciences - Botany - Pant Physiology
• Principal Investigator: Igor Cesarino
• Grantee: Lucas Xavier da Cunha
• 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

Lignin is a heterogeneous phenolic polymer that provides rigidity to the plant cell wall, being essential for the support and transport of water throughout the plant, in addition to acting in responses against herbivores and pathogens. However, lignin represents a bottleneck to the processing of plant biomass into bioproducts due to its recalcitrance, related to its physicochemical properties. The discovery of the flavone tricin as an authentic lignin monomer in grasses has opened new possibilities for the development of biotechnological tools targeting lignin. Currently, one of the aspects that remains uncertain regarding tricin biosynthesis in grasses refers to the activity of the flavone synthase enzymes FNSI and FNSII. While in corn both enzymes aree apparently responsible for the synthesis of flavones from flavanones, in rice this function appears to be performed exclusively by FNSII. This project aims to identify and characterize enzymes with FNS activity in the model grass Setaria viridis. Through heterologous expression, in vivo enzymatic assays and the characterization of transgenic lines silenced for FNS genes, we intend to determine (i) whether both FNSI and FNSII represent active pathways for the production of flavones and, specifically, tricin and ( ii) whether there is a preferential pathway in S. viridis. This project aims not only to understand key aspects of tricin biosynthesis in C4 grasses but also to generate possible genetic manipulation points for future biotechnological strategies for lignin bioengineering.