Deletion of ptn1 , a PTEN / TEP1 Orthologue, in Ustilago maydis Reduces Pathogenicity and Teliospore Development

The PTEN/PI3K/mTOR signal transduction pathway is involved in the regulation of biological processes such as metabolism, cell growth, cell proliferation, and apoptosis. This pathway has been extensively studied in mammals, leading to the conclusion that is a major tumor suppressor gene. orthologues have been characterized in a variety of organisms, both vertebrates and non-vertebrates, and studies of the associated PTEN/PI3K/mTOR pathway indicate that it is widely conserved. Studies in fungal systems indicated a role of in fungal defense mechanisms in , and in the developmental process of sporulation in . The present study was aimed at investigating the role of the ortholog, , in , the pathogen of maize. mutant strains where gene is deleted or overexpressed were examined for phenotypes associate with mating, virulence and spore formation. While the overexpression of had no substantial effects on virulence, deletion strains showed slight reductions in mating efficiency and significant reductions in virulence; tumor formation on stem and/or leaves were severely reduced. Moreover, tumors, when present, had significantly lower levels of mature teliospores, and the percent germination of such spores was similarly reduced. Thus, is required for these important aspects of virulence in this fungus.