The polysaccharide capsule of Cryptococcus neoformans—an opportunistic basidiomycete pathogen and the major etiological agent of fungal meningoencephalitis—is a key virulence factor that prevents its phagocytosis by host innate immune cells. However, the complex signaling networks for their synthesis and attachment remain elusive. In this study, we systematically analyzed capsule biosynthesis and signaling networks using C. neoformans transcription factor (TF) and kinase mutant libraries under diverse capsule-inducing conditions. We found that deletion of GAT201, YAP1, BZP4, and ADA2 consistently caused capsule production defects in all tested media, indicating that they are capsule-regulating core TFs. Epistatic and expression analyses showed that Yap1 and Ada2 control Gat201 upstream, whereas Bzp4 and Gat201 independently regulate capsule production. Next, we searched for potential upstream kinases and found that mutants lacking PKA1, BUD32, POS5, IRE1, or CDC2801 showed reduced capsule production under all three capsule induction conditions, whereas mutants lacking HOG1 and IRK5 displayed enhanced capsule production. Pka1 and Irk5 controlled the induction of GAT201 and BZP4, respectively, under capsule induction conditions. Finally, we monitored the transcriptome profiles governed by Bzp4, Gat201, and Ada2 under capsule-inducing conditions and demonstrated that these TFs regulate redundant and unique sets of downstream target genes. Bzp4, Ada2, and Gat201 govern capsule formation in C. neoformans by regulating the expression of various capsule biosynthesis genes and chitin/chitosan synthesis genes in a positive and negative manner, respectively. In conclusion, this study provides further insights into the complex regulatory mechanisms of capsule production-related signaling pathways in C. neoformans.
Bibliographical noteFunding Information:
This work was supported by the Bio & Medical Technology Development Program of the National Research Foundation (NRF) funded by the Korean government (MSIT) (no. 2021R1A2B5B03086596 and 2021M3A9I4021434), Republic of Korea, and by the Yonsei Signature Research Cluster Program of 2021-22-0014. This work was partly supported by the Strategic Initiative for Microbiomes in Agriculture and Food funded by the Ministry of Agriculture, Food, and Rural Affairs (no. 918012-4).
© 2022 Jang et al.
All Science Journal Classification (ASJC) codes
- Immunology and Microbiology(all)
- Microbiology (medical)
- Cell Biology
- Infectious Diseases