AUTHOR=Wu Ting , Fan Cheng-Li , Han Lian-Tao , Guo Yuan-Bing , Liu Tong-Bao 

TITLE=Role of F-box Protein Cdc4 in Fungal Virulence and Sexual Reproduction of Cryptococcus neoformans

JOURNAL=Frontiers in Cellular and Infection Microbiology

VOLUME=11

YEAR=2022

URL=https://www.frontiersin.org/journals/cellular-and-infection-microbiology/articles/10.3389/fcimb.2021.806465

DOI=10.3389/fcimb.2021.806465

ISSN=2235-2988

ABSTRACT=<p><italic>Cryptococcus neoformans</italic> is an opportunistic yeast-like pathogen that mainly infects immunocompromised individuals and causes fatal meningitis. Sexual reproduction can promote the exchange of genetic material between different strains of <italic>C. neoformans</italic>, which is one of the reasons leading to the emergence of highly pathogenic and drug-resistant strains of <italic>C. neoformans</italic>. Although much research has been done on the regulation mechanism of <italic>Cryptococcus</italic> sexual reproduction, there are few studies on the sexual reproduction regulation of <italic>Cryptococcus</italic> by the ubiquitin-proteasome system. This study identified an F-box protein, Cdc4, which contains a putative F-box domain and eight WD40 domains. The expression pattern analysis showed that the <italic>CDC4</italic> gene was expressed in various developmental stages of <italic>C. neoformans</italic>, and the Cdc4 protein was localized in the nucleus of cryptococcal cells. <italic>In vitro</italic> stress responses assays showed that the <italic>CDC4</italic> overexpression strains are sensitive to SDS and MMS but not Congo red, implying that Cdc4 may regulate the cell membrane integrity and repair of DNA damage of <italic>C. neoformans</italic>. Fungal virulence assay showed that although the <italic>cdc4</italic>Δ mutant grows normally and can produce typical virulence factors such as capsule and melanin, the <italic>cdc4</italic>Δ mutant completely loses its pathogenicity in a mouse systemic-infection model. Fungal mating assays showed that Cdc4 is also essential for fungal sexual reproduction in <italic>C. neoformans</italic>. Although normal mating hyphae were observed during mating, the basidiospores’ production was blocked in bilateral mating between <italic>cdc4</italic>Δ mutants. Fungal nuclei development assay showed that the nuclei failed to undergo meiosis after fusion inside the basidia during the bilateral mating of <italic>cdc4</italic>Δ mutants, indicating that Cdc4 is critical to regulating meiosis during cryptococcal mating. In summary, our study revealed that the F-box protein Cdc4 is critical for fungal virulence and sexual reproduction in <italic>C. neoformans</italic>.</p>