Program Book - 27th Fungal Genetics Conference

CONCURRENT SESSION ABSTRACTSThursday, March 14 3:00 PM–6:00 PMNautilusFungal Volatiles and Organic Compounds as Signaling AgentsCo-chairs: Joan Bennett and Richard SplivalloFungi reacting to rhizobacterial volatiles. Birgit Piechulla, Piyali Das, Uta Effmert. University of Rostock, Rostock, Germany.Microorganisms, similar as other organisms are able to synthesize and release volatile organic compounds (VOCs), which are responsible forcharacteristic blends or aromas of for example foodstuff such as wine and cheese as well as spoiled meat. The capability of microorganisms to emitcomplex volatile mixtures is tremendous. More than 800 volatiles are presently known that are emitted by microorganisms (database of volatiles ofmicroorganisms DOVE-MO). Beside the wealth of volatile emissions, to date not much is known about the biological functions of these compounds. Tostudy volatile-mediated interactions of plant associated bacteria and fungi, various rhizobacteria and phytopathogenic fungi were co-cultivated in bipartitePetri dishes, which allow only volatiles to traverse from one to the other compartment. The volatiles of Serratia, Stenotrophomonas, Pseudomonas,Burkholderia and Staphylococcus inhibited the growth of Aspergillus, Fusarium, Microdochium, Neurospora, Rhizoctonia, Phaecilomyces, Penicillium,Phoma, Sclerotinia, Trichoderma and Verticillium in species specific manner. The reactions of Sclerotinia scleotiorum to Serratia sp. 4Rx13 volatiles werestudied in more detail, e.g. radial growth, biomass formation, catalase activity and lipid peroxidation. Furthermore, the volatile mixture of Serratia sp.4Rx13 was studied using headspace collection systems and GCMS analysis. Ca. 100 volatiles were separated, some of them were identified, most of themremain unknowns or structures have to be elucidated. References: Kai et al. (2007) Arch. Microbiol. 187:351-360 Vespermann et al. (2007) Appl. Environ.Microbiol. 73:5639-5641 Kai et al. (2010) Appl. Microbiol. Biotechnol. 88:965-976 Effmert et al. (2012) Chem. Ecol. 38:665-703.Enhancement of plant growth and stress resistance by Fusarium volatile organic compounds: A novel mechanism mediating plant-fungal interactions.Seogchan Kang 1,3 , Vasileios Bitas 1,3 , Nate McCartney 2,3 , Jim Tumlinson 2,3 . 1) Plant Pathology & Environmental Microbiology, Pennsylvania State Univ,University Park, PA; 2) Entomology, Pennsylvania State Univ, University Park, PA; 3) Center for Chemical Ecology, Pennsylvania State Univ, University Park,PA.Every organism employs an elaborate network of signaling pathways for sensing stimuli from surrounding environments and neighboring organisms andtranslating them into specific molecular and cellular responses. Production and perception of a vast array of secreted proteins and metabolites plays keyroles in this mechanism. A group of secreted molecules that are ubiquitous but often overlooked is volatile organic compounds (VOCs). VOCs can travel farfrom their point of production through the atmosphere as well as porous soils, making them ideal signaling molecules for mediating organismalinteractions without physical contact. Roles of animal- and plant-derived VOCs in directing animal behaviors and roles of plant VOCs in chatters of “talkingtrees” are well known and serve critical roles in diverse ecological processes. In contrast, the available knowledge of microbial VOCs as semiochemicals islimited and mostly circumstantial. Multiple isolates of Fusarium oxysporum, a soil-borne, cosmopolitan fungus that often resides in the rhizosphere ofmany plants, produce unknown VOCs that drastically enhance the growth and stress resistance of Arabidopsis thaliana. Other Fusarium species alsopromoted Arabidopsis growth. Molecular and cellular changes underpinning the Fusarium VOC-mediated signaling will be discussed. Given the vastdiversity of fungi in nature and the critical importance of fungal communities for the ecology and fitness of plants, VOC-mediated signaling is a mostlyuncharted frontier, waiting for systematic exploration.The Role of Quorum-sensing Molecules in Interactions between Candida albicans and its Host. Jessica C. Hargarten 1 , Thomas M. Petro 2 , Kenneth W.Nickerson 1 , Audrey L. Atkin 1 . 1) School of Biological Sciences, University of Nebraska, Lincoln, Lincoln, NE; 2) Department of Oral Biology, University ofNebraska Medical Center, Lincoln, NE.Candida albicans is a polymorphic fungus that is capable of causing the life threatening disease Candidiasis once it reaches the bloodstream of asusceptible host. The capability to switch between morphologies, and its ability to synthesize and secrete the quorum sensing molecule (QSM) farnesol areknown virulence factor. Previously, we showed that C. albicans mutants that produced less farnesol are less pathogenic to mice than their parental strainin a tail vein assay. Also, oral administration of farnesol to the mice prior to infection increased mortality. In contrast, farnesol blocks the yeast to myceliatransition in vitro, which should have a protective effect. These observations pose the dilemma of finding a mechanism whereby a molecule which blocksthe yeast to mycelia transition can also act as a virulence factor. We hypothesize that farnesol functions as a virulence factor by modulating the hostinnate immune response. Distinct Candida morphologies elicit different host immune responses. Both white and opaque cells stimulate leukocytemovement, but only white cells secrete a small molecular weight chemoattractant that draws the leukocyte directly towards the white cell and stimulatesengulfment by mouse macrophages. The white cells are also less susceptible to killing by human macrophages and neutrophils than opaque cells, possiblydue to their increased capabilities of escape once phagocytosed. The chemical identity of this chemoattractant is currently unknown, but the reasonbehind its continued secretion by white cells is intriguing. One likely candidate is farnesol because opaque cells, unlike white cells, do not accumulatedetectable levels of farnesol. Macrophages are capable of detecting and responding to exogenous farnesol. Earlier our group reported that farnesolstimulates the expression of both pro-inflammatory and regulatory cytokines by mouse macrophage. The production of these warning signals is animportant indicator of how the body ultimately hopes to clear the infection. Others have shown that farnesol suppresses the anti-Candida activity ofmacrophages through its cytotoxic effects, thus making it all the more difficult to eliminate the fungus early in infection. Here we report the in vitro role offarnesol and other known QSM in macrophage chemotaxis and relative phagocytosis of C. albicans.58