Cryptococcus neoformans is an opportunistic fungal pathogen that has several well-described virulence determinants. A
polysaccharide capsule and the ability to produce
melanin are among the most important. Melanization occurs both in vitro, in the presence of
catecholamine and
indole compounds, and in vivo during the
infection. Despite the importance of
melanin production for cryptococcal virulence, the component and mechanisms involved in its synthesis have not been fully elucidated. In this work, we describe the role of a G1/S
cyclin (Cln1) in the melanization process. Cln1 has evolved specifically with
proteins present only in other basidiomycetes. We found that Cln1 is required for the cell wall stability and production of
melanin in C. neoformans. Absence of melanization correlated with a defect in the expression of the LAC1 gene. The relation between cell cycle elements and melanization was confirmed by the effect of drugs that cause cell cycle arrest at a specific phase, such as
rapamycin. The cln1 mutant was consistently more susceptible to oxidative damage in a medium that induces melanization. Our results strongly suggest a novel and hitherto unrecognized role for C. neoformans Cln1 in the expression of virulence traits.