Autophagy Regulates Fungal Virulence and Sexual Reproduction in Cryptococcus neoformans

Abstract

Autophagy (macroautophagy) is an evolutionarily conserved degradation pathway involved in bulk degradation of cytoplasmic organelles, old protein, and other macromolecules and nutrient recycling during starvation. Extensive studies on functions of autophagy-related genes have revealed that autophagy plays a role in cell differentiation and pathogenesis of pathogenic fungi. In this study, we identified and characterized 14 core autophagy machinery genes (ATGs) in C. neoformans. To understand the function of autophagy in virulence and fungal development in C. neoformans, we knocked out the 14 ATGs in both α and a mating type strain backgrounds in C. neoformans, respectively, by using biolistic transformation and in vivo homologous recombination. Fungal virulence assay showed that virulence of each atg mutants was attenuated in a murine inhalation systemic-infection model, although virulence factor production was not dramatically impaired in vitro. Fungal mating assays showed that all the 14 ATGs are essential for fungal sexual reproduction as basidiospore production was blocked in bilateral mating between each atg mutants. Fungal nuclei development assay showed that nuclei in the bilateral mating of each atg mutants failed to undergo meiosis after fusion, indicating autophagy is essential for regulating meiosis during mating. Overall, our study showed that autophagy is essential for fungal virulence and sexual reproduction in C. neoformans, which likely represents a conserved novel virulence and sexual reproduction control mechanism that involves the autophagy-mediated proteolysis pathway.

The Cryptococcus neoformans Flc1 Homologue Controls Calcium Homeostasis and Confers Fungal Pathogenicity in the Infected Hosts

“…Our data suggest that Flc1 regulates vacuolar fusion under stress conditions. Autophagy is a catabolic process induced by diminishment of nutrient availability that requires vacuolar fusion mediated by the TOR pathway ( 39 ). We hypothesized that C. neoformans Flc1 plays a role in the starvation response by regulating TOR-mediated vacuolar fusion and autophagy.…”

Nutrition-Associated Processes Govern Fungal Pathogenicity

“…Studies have shown that it is crucial to C. neoformans infection (Figure 1). A recent study surveyed an in vivo virulent phenotype seen in 14 C. neoformans autophagy gene knockout strains, and the results showed that autophagy is essential for fungal survival in the host 33 . These mutants also showed impaired basidiospore production and the inability to undergo meiosis 33 .…”

“…A recent study surveyed an in vivo virulent phenotype seen in 14 C. neoformans autophagy gene knockout strains, and the results showed that autophagy is essential for fungal survival in the host 33 . These mutants also showed impaired basidiospore production and the inability to undergo meiosis 33 . The VPS34 gene in C. neoformans is involved in the autophagy of ascomycete yeast, regulating the formation of autophagy-related 8-labeled (ATG8-labeled) vesicles 34 .…”

“…33 These mutants also showed impaired basidiospore production and the inability to undergo meiosis. 33 The VPS34 gene in C. neoformans is involved in the autophagy of ascomycete yeast, regulating the formation of autophagy-related 8-labeled (ATG8labeled) vesicles. 34 The disruption of this gene led to a significant reduction in C. neoformans toxicity.…”

Dynamic Regulation of Peroxisomes and Mitochondria during Fungal Development

“…Autophagy also plays major roles during sexual development in fungi [ 179 , 188 , 189 , 190 , 191 , 192 ]. During sexual reproduction, a developmental specific removal of peroxisomes takes place during ascospore development in P. anserina .…”