ABSTRACT: The infection process is characterized by the simultaneous production of metabolites by both the pathogen and the host. Recently, it has been discovered that molecules generated during sulfur metabolism, mainly hydrogen sulfide (H₂S), play a key role in regulating which organism will prevail during pathogenesis. This phenomenon has been described in bacterial and filamentous fungi infections. Ustilago maydis is a saprophytic fungus that infects maize plants and causes crop losses on a global scale. Although the role of various biomolecules produced by U. maydis during the infection process has been described (ustilagic acid, polyketides, and lipids among others), the function of sulfur-containing compounds, like cysteine and H₂S in this process remains uncharacterized. Here, U. maydis was incubated in a culture medium that promotes H₂S production. The cytoplasmic extract was then obtained, and proteins were extracted and enzymatically digested with trypsin. The resulting peptides were separated using a UPLC NanoAcquity M-Class system. The spectra of these peptides were acquired using MS with electrospray ionization (ESI), employing a data-independent acquisition (DIA) approach and multiplexed high-definition tandem mass spectrometry (HD-MS/MS). Thus, a total of 1,706 proteins were identified and quantified using an internal standard and the intensity of the most abundant peptides, analyzed with Progenesis QI software v4.2.1 and an Ustilago maydis FASTA database (downloaded from UniProt, UP000000561, containing 6,805 protein sequences). Among the identified proteins, 290 were upregulated, while 160 were downregulated. Upon incubation in the aforementioned medium, proteins related to mitochondrial respiration, proteasomal protein degradation, and fatty acid metabolism were upregulated, whereas proteins associated with oxidative stress response, the pentose phosphate pathway (PPP), and translation were downregulated. Additionally, an increase in proteins related to the infectious process, such as endoxylanases and proteinases, was also observed. Thus, this study describes for the first time the role of cysteine metabolism regulation in proteome dynamics in Ustilago maydis.
Emilio Espinoza-Simón 