Biofilms and extracellular vesicles of Fusarium verticillioides and their implications for virulence

Abstract

Extracellular vesicles (EVs) have substantial functional consequences in fungi because they internalize bioactive molecules (e.g., proteins, nucleic acids, and secondary metabolites) from their source cells. Internalized contents can be released into the extracellular environment, where they can either persist for long periods of time because they are protected by the vesicle membrane from potentially harmful agents (e.g., degradative enzymes), ensuring their potency, or they can be readily absorbed by recipient cells, causing a variety of physiological effects. In fungi such as Candida albicans, EVs enhance virulence factor production such as biofilms, a matrixed and architecturally complex microbial community typically attached to a surface and embedded in a gelatinous matrix composed of extracellular polymeric substances (EPS). As EVs are also produced by biofilms, which are a key virulence determinant in nearly all microbial pathogens, a thorough understanding of their role in biofilm formation is key. During this study, it was first thoroughly characterized biofilm formation in the important disease-causing agent in the maize crop, Fusarium verticillioides. Then, EVs were recovered and characterized from free-living (planktonic) cells and biofilms of Fusarium verticillioides, offering fresh information on how key signals (e.g., nutrients, enzymes, genes, RNA, DNA, metabolites, and so on) are exchanged to contribute to biofilm development and structural integrity. Given that both EV and biofilm biology in phytopathogens are poorly understood, these findings will greatly contribute to this knowledge gap and serve as a reference point for further research into biofilms as a poorly represented virulence determinant in fungal phytopathogens.