RESUMO
White-rot fungus Phanerochaete chrysosporium, a ligninolytic basidiomycete, was studied to identify iron-responsive genes. Using the differential display reverse transcription PCR technique (DDRT-PCR), a total of 97 differentially expressed cDNA fragments were identified by comparing band intensities among fingerprints obtained from mycelia cultivated in iron-deficient and iron-replete media. Transcripts induced under iron-starvation exhibited homologies to: a modular polyketide synthase, a TonB protein, a probable transmembrane protein, a putative ABC transporter permease and a HSP70-related heat-shock protein. Modular polyketide synthase and TonB proteins are normally expressed under iron-starvation and are known to be involved in biosynthesis and transport of siderophores respectively. Also, a deduced protein with 96% similarity to a precursor of the well-known P. chrysosporium lignin peroxidase was identified under iron-deficiency. Two DDRT-PCR products confirmed their iron-induced expression. One was homologue to the CNOT3, which is a global regulator of RNA polymerase II transcription and has been implicated in multiple roles in the control of mRNA metabolism. The other was similar to the Schizosaccharomyces pombe putative proteasome maturation factor upm1. In conclusion, the majority of iron-responsive P. chrysosporium transcripts isolated in the DDRT-PCR encode proteins involved in iron acquisition, especially members of biosynthesis and transport of iron chelators.
