Ferrochelatase is a conserved downstream target of the blue light-sensing White collar complex in fungi

Abstract

Light is a universal signal perceived by organisms, including fungi, in which light regulates common and unique biological processes depending on the species. Previous research has established that conserved proteins, originally called White collar 1 and 2 from the ascomyceteNeurospora crassa, regulate UV/blue light sensing. Homologous proteins function in distant relatives ofN. crassa, including the basidiomycetes and zygomycetes, which diverged as long as a billion years ago. Here we conducted microarray experiments on the basidiomycete fungusCryptococcus neoformansto identify light-regulated genes. Surprisingly, only a single gene was induced by light above the commonly used twofold threshold. This gene,HEM15, is predicted to encode a ferrochelatase that catalyses the final step in haem biosynthesis from highly photoreactive porphyrins. TheC. neoformansgene complements aSaccharomyces cerevisiae hem15Δ strain and is essential for viability, and the Hem15 protein localizes to mitochondria, three lines of evidence that the gene encodes ferrochelatase. Regulation ofHEM15by light suggests a mechanism by whichbwc1/bwc2mutants are photosensitive and exhibit reduced virulence. We show that ferrochelatase is also light-regulated in awhite collar-dependent fashion inN. crassaand the zygomycetePhycomyces blakesleeanus, indicating that ferrochelatase is an ancient target of photoregulation in the fungal kingdom.