Understanding the interaction between the phytopathogen Austropuccinia psidii and the Syzygium jambos host through untargeted metabolomics

Stephanie Nemesio da Silva1, Carolina Alessandra de Almeida Hayashibara2, Júlio César Jeromino Barbosa1, Maria Carolina Quecine2, Taicia Pacheco Fill1

1. Institute of Chemistry, UNICAMP ; Campinas - SP, Brazil
2. Department of Genetics , ESALQ-USP; Piracicaba - SP, Brazil

Keywords: Austropuccinia psidii, Syzygium jambos, Metabolomics, Specialized metabolites.

Myrtle rust, a disease caused by the biotrophic fungus Austropuccinia psidii, is recognized as the major threat to the Myrtaceae family. Infections caused by A. psidii have been reported in 539 susceptible species worldwide, including crops with economic importance and native forest species. Nowadays, control methods are based on selecting resistant cultivars or applying fungicides, but these approaches are not feasible for natural ecosystems. Thus, understanding the plant-pathogen interaction can contribute to developing novel, efficient, and environmentally friendly biocontrol strategies.

Therefore, we applied a metabolomics workflow (Figure 1) to investigate the chemical mechanisms involved in the interaction pathogen-host at 24, 144, and 336 h post-inoculation. Extracted metabolites from fresh leaf samples were analyzed by UHPLC-ESI(+)-MS/MS and GC-EI-MS, and the data processed using mzmine software. Statistical analyses were conducted on the MetaboAnalyst platform (https://www.metaboanalyst.ca), and the molecular networks were obtained through the FBMN tool on the GNPS2 platform (https://gnps2.org).

Figure 1. Metabolomics workflow applied to analyze infected S. jambos leaves with A. psidii.

According to the PCA of Figure 1, host specialized metabolism is altered by fungal infection at all times evaluated. Statistical and molecular networking analysis detected changes in the biosynthesis of polyphenols, fatty acids, and terpenes (including the sesquiterpenes with m/z 204 and m/z 220). Specifically, a decrease in the content of myricetin-3-galactoside (m/z 481.0975) and analogues was observed during the establishment of fungal infection. This class of metabolites exhibits antioxidant biological activity and is commonly involved in plant defense mechanisms. The results indicate that in susceptible cultivars, such as S. jambos, the pathogen could alter flavonoid biosynthesis and evade this plant\'s primary defense system. This is the first step toward understanding the mechanisms of action for myrtle rust.   

Agradecimentos: EECF Itatinga - ESALQ/USP, FAPESP, CAPES, and CNPQ.