Functional characterization of the ALDEHYDE DEHYDROGENASE2B (ALDH2B) subfamily in the model grass Setaria viridis (L.) P.Beauv.: implications for the phenolic metabolism

• Grant number: 24/10125-0
• Support Opportunities: Scholarships in Brazil - Doctorate
• Start date: December 01, 2024
• End date: October 31, 2027
• Field of knowledge: Biological Sciences - Botany - Pant Physiology
• Principal Investigator: Igor Cesarino
• Grantee: Gabriel Garon Carvalho
• 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 phenolic metabolism is an important source of specialized metabolites with essential functions for plants. Among its main products, two of the most important are lignin, a biopolymer deposited in the secondary walls that provides mechanical rigidity to supportive tissues and waterproofs the xylem vessels, and benzenoids, aromatic carboxylic acids with functions in plant development and in plant responses to the environment. In the scope of the bioeconomy, lignin is the major bottleneck in the conversion of plant biomass into biofuels and other biomaterials. Therefore, a better understanding of the phenolic and lignin metabolisms is essential for the development of crops optimized for the bioeconomy. The Aldehyde Dehydrogenase (ALDH) superfamily is formed by enzymes involved in the metabolism of aldehydes, converting them into their respective carboxylic acids. Some members of the ALDH2 subfamily are capable of metabolizing phenolic aldehydes recognized as intermediates in lignin biosynthesis, while others are involved in benzenoid metabolism. However, the importance of the ALDH2 subfamily in the phenolic metabolism remains poorly explored. Very few genes encoding ALDH2s have been properly characterized, and most of them without evidence using reverse genetics. Furthermore, benzenoid biosynthesis remains poorly understood, especially in grasses. The objective of this project is to identify and characterize the genes of the ALDH2B subfamily involved in the metabolism of phenolic aldehydes in the model grass Setaria viridis, especially those involved in the metabolism of benzenoids. Firstly, their gene expression pattern in different tissues and cell types of S. viridis will be determined using RT-qPCR and in situ hybridization assays. Recombinant enzymes will be produced in Escherichia coli and purified to perform in vitro enzymatic assays, in order to determine their ability to metabolize phenolic aldehydes. Finally, the function of the ALDH2B genes in planta will be evaluated through their overexpression in S. viridis. The transgenic lines will be characterized in terms of biomass parameters, secondary wall and lignin deposition, and changes in metabolomic profiles. The data generated in this project will be important not only to contribute to a better understanding of the phenolic metabolism in grasses, but also to the development of biotechnological strategies for the bioeconomy.