Objective: Cryptococcus neoformans is an opportunistic human fungal pathogen that primarily infects immunocompromised patients. The most distinctive feature of C. neoformans is that it contains a highly regulated major virulence factor, the polysaccharide capsule. We demonstrate in this paper that a copper-dependent transcription factor gene CUF1 has a negative role in capsule biosynthesis.
Methods: Colony morphology, Indian inking staining microscopy, volume of cell suspension observation, weight of capsule produced by the disruption mutant of CUF1 and the wild type control.
Results: The mutant produced a mucoid large colonies compared to that of the wild type. Capsule size was larger as shown by microscopy. The mutant had a larger volume with the same number of cells. And the mutant produced more capsule as determined by weight of dried extracellular polysaccharides. Iron repletion could suppress the capsule overproduction phenotype of the deltacuf1 mutant.
Conclusion: The copper responsive transcription factor 1 (Cuf1) negatively regulates capsule biosynthesis in C. neoformans. Cuf1 may act via modulating iron acquisition through the high-affinity iron uptake pathway.