Metabolomic analysis of the effects of Arginase-like inhibitors in the regulation of neutral lipids synthesis in microalgae

• Grant number: 24/02042-7
• Support Opportunities: Scholarships abroad - Research Internship - Scientific Initiation
• Start date: July 01, 2024
• End date: October 31, 2024
• Field of knowledge: Biological Sciences - Biochemistry - Metabolism and Bioenergetics
• Principal Investigator: Flavia Vischi Winck
• Grantee: Leandro Luis Lavandosque
• Supervisor: Junyoung Park
• Host Institution: Centro de Energia Nuclear na Agricultura (CENA). Universidade de São Paulo (USP). Piracicaba , SP, Brazil
• Institution abroad: University of California, Los Angeles (UCLA), United States
• Associated to the scholarship: 22/15431-6 - Proteomics analysis of Arginase-like function inhibition effects on the regulation of neutral lipids synthesis in microalgae, BP.IC

Abstract

Microalgal biomass has received attention as a possible feedstock of sustainable biomass for neutral lipids (Triacylglycerols/TAGs) production to attend the biofuel industry in the future. Among the many photosynthetic microalgae species already investigated, Chlamydomonas reinhardtii has been defined as a model organism for the investigation of cellular metabolism and photosynthesis-related mechanisms. The experiments in these fields revealed that the production of TAGs and their accumulation in Chlamydomonas happens in response to different abiotic stress conditions, such as nitrogen deprivation or salt stress. However, these conditions also lead to cell quiescence, which on some days commits the cells to die, configuring a biotechnological issue to ensure the production of these organisms, related to the complete loss of microorganisms in each process batch. Therefore, efforts in understanding the regulatory mechanisms associated with this phenotype can reveal metabolic and regulatory targets for metabolic engineering, which could enhance the production of neutral lipids in a feasible and sustainable approach, while revealing deep aspects of the natural regulatory control of lipids accumulation and cell growth in eukaryotic cells. Recent results from our research group obtained from integrative analysis of the proteome and metabolome of microalgae under nitrogen deprivation conditions pointed to a set of metabolites and proteins that may be associated with the regulation of the TAGs overaccumulation under abiotic stress conditions, especially nitrogen deprivation. Biological network analysis suggested that amino acids degradation cycles, especially Arginine catabolism, may be inhibited under nitrogen deprivation generating nitric oxide in consequence of the inhibition of a hypothetical Arginase-Like function, which may be a central hub of the metabolic regulation of cell growth and TAGs accumulation. However, an Arginase gene has not been annotated in the C. reinhardtii genome yet, while this gene has been reported in land plants as having a functional role related to the production of nitric oxide through arginine catabolism. This hypothesis was reinforced by our observations of increased production of nitric oxide (NO) in cells under nitrogen deprivation and enhanced accumulation of neutral lipids in Chlamydomonas treated with arginase inhibitors norvaline, ornithine, and valine. These results also suggest that the amino acids or amino acid transporters/permeases may be performing or participating in a signaling cascade linked to the induction of this phenotype. The inhibition of the function of Arginase has been associated with the higher production of NO via nitric oxide synthase (NOS) enzymes in animals, but it is still under debate in land plants and has recently been described in yeast. Considering the previous reports on arginase activity in Chlamydomonas, and the metabolic outcomes of our previous experimental results, the present proposal seeks to identify the molecules that originated from the arginine catabolism in control conditions and under arginase inhibitor supplementation. The identification of these metabolites can contribute to the elucidation of regulatory modules associated with the hypothetical Arginase function, and how they could be involved in the control of TAG accumulation in microalgae.