Fungi generate a wide range of extracellular oxidative enzymes and reactive metabolites, collectively known as the secretome, that synergistically drive carbon (C) degradation in the environment. While secretome studies of model organisms have greatly expanded our knowledge of these oxidative enzymes, few have extended secretome characterization to environmental isolates or directly compared temporal patterns of enzyme utilization among phylogenetically diverse species. Thus, the mechanisms of C degradation by many ubiquitous soil fungi remain poorly understood.
Results/Conclusions
Here we use a combination of quantitative iTRAQ proteomics and custom bioinformatic analyses to compare the protein composition of the secretomes of four Mn(II)-oxidizing Ascomycete fungi over a three-week time course. We demonstrate that although the fungi produce a similar suite of extracellular enzymes, they exhibit striking differences in the regulation of these enzymes among species and over time, revealing species-specific and temporal shifts in C utilization strategies as they degrade the same substrate. Specifically, our findings suggest that Paraconiothyrium sporulosum AP3s5-JAC2a and Alternaria alternata SRC1lrK2f employ sequential enzyme secretion patterns concomitant with decreasing resource availability, Stagonospora sp. SRC1lsM3a preferentially degrades proteinaceous substrate before switching to carbohydrates, and Pyrenochaeta sp. DS3sAY3a utilizes primarily peptidases to aggressively attack C sources in a concentrated burst. This work highlights the diversity of operative metabolic strategies among cellulose-degrading Ascomycetes and enhances our understanding of their role in C turnover in the environment.