Antioxidant systems in seeds: Functions of 1-Cys Peroxiredoxin and Ascorbate during embryogenesis and germination.

• Grant number: 19/15924-0
• Support Opportunities: Scholarships in Brazil - Post-Doctoral
• Start date: September 01, 2019
• End date: October 31, 2024
• Field of knowledge: Biological Sciences - Biochemistry - Metabolism and Bioenergetics
• Principal Investigator: Luis Eduardo Soares Netto
• Grantee: Ana Luiza Dorigan de Matos Furlanetto
• Host Institution: Instituto de Biociências (IB). Universidade de São Paulo (USP). São Paulo , SP, Brazil
• Associated research grant: 13/07937-8 - Redoxome - Redox Processes in Biomedicine, AP.CEPID
• Associated scholarship(s): 21/14830-1 - Investigating the roles of peroxiredoxins and ascorbate on the development and germination of Arabdopsis thaliana seeds, BE.EP.PD

Abstract

Our research group investigates the mechanisms related to cysteine-based peroxidases, such as peroxiredoxin (Prx) enzymes. We have shown that sulfenic acids (R-Cys-SOH) in enzymes of the 1-Cys Prx class can be reduced by ascorbate (vitamin C) (Monteiro et al., 2007 Proc. Natl. Acad. Sci USA), challenging the paradigm that 1-Cys Prx are specifically reduced by thiols (RSH). Thus sulfenic acid / ascorbate represents a new redox pair, whose biological relevance still needs to be assessed.Our current challenge is to demonstrate that ascorbate can compete with other cellular reducing systems (i.e. Trx or Grx / GSH) for sulfenic acid reduction. The concentrations of these reductants in the different cellular compartments is one of the factors that can determine which system will prevail.Plants present very high concentrations of ascorbate (3-30 mM) in several cell compartments (Zechmann et al., 2011, Zechmann 2014). On the other hand, 1-Cys Prx of plants is preferentially expressed in embryonic tissues, mainly in nuclei of seed cells and in some cases diffused in the cytoplasm (Stacy et al., 1996, 1999). Other reductive systems in addition to ascorbate, such as Thioredoxin (Trx) and Trx Reductase (TrxR) are co-localized with PER1 during seed development, including in nuclei of germinating seeds under stress (Pulido et al., 2009).Therefore, understanding the biological significance of 1-Cys Prx reductants requires an integrated analysis, involving determination of kinetic parameters (such as kcat and Km); the distribution of the possible reductants during the life cycle of the seeds; in addition to phenotypes associated with genetic mutants. The antioxidant systems of seeds of two plants: Arabidopsis thaliana (a model organism) and Araucaria angustifolia (Brazilian pine) will be analyzed, with the collaboration of research groups led by professors Marie-Anne Van Sluys (PhD) and Eny I.S. Floh (PhD) from the Department of Botany of University of São Paulo's Institute of Biosciences (IB-USP).