Application of 6-nitrocoumarin as a substrate for the fluorescent detection of nitroreductase activity in Sporothrix schenckii

Ste20 is crucial for dimorphic switching of sporothrix schenckii and affects its global transcriptome

Sporothrix schenckii induced sporotrichosis has gained importance in recent years because of its worldwide prevalence. The dimorphic switching process is required for the pathogenesis of S. schenckii. Previously, we found that STE20-like protein kinase (SsSte20) was overexpressed in the early yeast stage, but not in the mycelial stage of S. schenckii, which suggested its involvement in morphogenesis of this fungal pathogen. It remains unclear, however, whether SsSte20 is essential for dimorphic switching of S. schenckii and what are its related genes. In this study, the function of SsSte20 was investigated using double-stranded RNA interference (dsRNAi) mediated by Agrobacterium tumefaciens. We evaluated its effects on normal asexual development, yeast-phase cell formation, and cell wall composition and integrity. In addition, by transcriptome analysis of the SsSte20 knockdown (SsSte20-i) mutant and the standard S. schenckii strain, we further investigated the genes and pathways that were affected by SsSte20. Our results showed that inactivation of SsSte20 significantly affected the growth and internal components of S. schenckii conidia and impaired the dimorphic switching process. RNA transcriptome analysis of the standard S. schenckii strain and the SsSte20-i mutant revealed that SsSte20 inhibition affected the genes that were not only involved in the biological process, but also in the cellular component, and the molecular functions of S. schenckii. It mainly affected the expression of iron/ion-binding transporter genes, oxidation-reduction-related genes, 1, 3-beta-glucosidase, and methylsterol monooxygenase, which are highly associated with environmental information processing and the biosynthesis of cell wall components. Overall, our research supports the claim that SsSte20 plays an essential role in the dimorphism of S. schenckii and affects its global transcriptome.

Sporothrix schenckii complex biology: environment and fungal pathogenicity

Sporothrix schenckii is a complex of various species of fungus found in soils, plants, decaying vegetables and other outdoor environments. It is the aetiological agent of sporotrichosis in humans and several animals. Humans and animals can acquire the disease through traumatic inoculation of the fungus into subcutaneous tissue. Despite the importance of sporotrichosis, it being currently regarded as an emergent disease in several countries, the factors driving its increasing medical importance are still largely unknown. There have only been a few studies addressing the influence of the environment on the virulence of these pathogens. However, recent studies have demonstrated that adverse conditions in its natural habitats can trigger the expression of different virulence factors that confer survival advantages both in animal hosts and in the environment. In this review, we provide updates on the important advances in the understanding of the biology of Spor. schenckii and the modification of its virulence linked to demonstrated or putative environmental factors.