n sep4 mutant strain. Whether this result is related to the above described presence of septins at basal locations is not known, although is an appealing possibility. Germination of teliospores is affected in septin mutant strains As we mentioned above, septins were dispensable for virulence in U. maydis and plants infected by septin mutants developed tumors that eventually were filled by 24195657 melanized diploid teliospores. In the field, germination of the air-borne diploid teliospores is the first step in the infection process and therefore germination of teliospores is required to fulfill the life cycle in this fungus. U. maydis teliospore germination is a complex process that includes a switch from dormancy to physiological activity, the rupture of the thick cell wall, extension of a tubular promycelium and the completion of meiosis to produce haploid cells. Emergence of the promycelium implies the establishment of a new polarity axis, and therefore a role of septins in this process could be predicted. In fact, a previous report 520-26-3 already described defects in germination of teliospores obtained from sep3 mutant strains. To extend these observations to the other septins, collected tumors from infected plants with wild-type or septin mutant cells were ground and teliospores isolated. Teliospores preparations were plated onto complete medium agar-coated slides and incubated for 24 hours at two different temperatures to observe and quantify teliospore germination. Wild-type teliospores germinated by extending a promycelium, with subsequent meiosis and the formation of haploid progeny as buds from the promycelium. However, although a substantial proportion of septin mutant teliospores were able to germinate at both temperatures, they showed abnormal morphology including swelling of promycelium and aberrant shape. Also it was noticeable that all septin mutants produced more than one germination tube per germinated teliospore at both temperatures. The proportion of this defect was 90% in average for the mutants at both temperatures and 6% and 11% in wild-type teliospores. September 2010 | Volume 5 | Issue 9 | e12933 Septins in Corn Smut Fungus 7 September 2010 | Volume 5 | Issue 9 | e12933 Septins in Corn Smut Fungus In spite of these defects during germination, mutant teliospores were able to produce haploid progeny. Discussion This paper investigates the role of septins in the life cycle of U. maydis and 
comes to three main conclusions. The first one concerns to the presence of three distinct septin structures coexisting in the same cell in U. maydis, which were observed using functional GFP-tagged alleles. Two of these structures, located at the bud neck and the bud tip, were similar to other structures already described in fungi, while the third one, fibers running from pole to pole, has been less described. The second finding relates to the role that septins may have in morphogenesis in U. maydis. We observed that although not essential for growth, mutant cells lacking septins display an aberrant morphology that cannot be explained simply invoking a defect in bud neck formation, arguing additional roles of septins during morphogenesis 16985061 in U. maydis. Finally, our third main conclusion refers to the ability of septin mutants to infect plants that contrasts with the impaired virulence of septin mutants described in other pathogenic fungi. Our discussion briefly reviews our evidence for these September 2010 | Volume 5 | Issue 9 | e12933 Septins in
