has role has_role has role gene as virulence factor in pathogen has role has_role has role Cryptococcus neoformans var. grubii H99 gene MUTATION: The MET6 gene showed a substantial induction in response to methionine and a dramatic transcriptional induction in response to homocysteine [PMID:15347759]. 5331 5321 MUTATION: The Cryptococcus neoformans ILV2 gene, encoding acetolactate synthase. The ilv2 mutants were auxotrophic for isoleucine and valine and the auxotrophy was satisfied by these amino acids only when proline, and not ammonium, was the nitrogen source, indicating nitrogen regulation of amino acid transport [PMID:15133116]. virulence factor gene role