A Gene That Encodes a Product with Similarity to Dioxygenases is Highly Expressed in Teliospores of Ustilago Maydis

The phytopathogenic basidiomycete Ustilago maydis produces sexual teliospores only after infection of its host plant, maize. To investigate the process of spore formation, we have isolated Ssp1, a protein that is abundantly expressed in mature teliospores. The corresponding gene, ssp1, is expressed at low levels in haploid sporidia; however, transcriptional levels are drastically induced in mature teliospores. Transcriptional regulation of ssp1 involves positive and negative promoter elements, and is subject to control by the cAMP signaling cascade and histone deacetylase-mediated repression. Ssp1 shows similarity to linoleate diol synthase, a fatty acid dioxygenase from the fungus Gaeumannomyces graminis. In agreement with this presumed function, Ssp1 is localized on lipid bodies in germinating teliospores, suggesting a role in the mobilization of storage lipids.