Program Book - 27th Fungal Genetics Conference

CONCURRENT SESSION ABSTRACTSSynergistic interactions between leaf-cutting ants and their fungal symbiont facilitate degradation of plant substrate. Morten Schiøtt 1 , Henrik H. de FineLicht 2 , Adelina Rogowska-Wrzesinska 3 , Pepijn Kooij 1 , Peter Roepstorff 3 , Jacobus J. Boomsma 1 . 1) Department of Biology, University of Copenhagen,Copenhagen, Denmark; 2) Department of Mycology, Lund University, Lund, Sweden; 3) Department of Biochemistry and Molecular Biology, University ofSouthern Denmark, Odense, Denmark.About 50 million years ago a single ancestor of today’s more than 230 species of fungus-growing ants committed herself irreversibly to farming fungi forfood instead of being a hunter-gatherer as most other ants. However, the white-rot litter decomposing Leucocoprini (Agaricales) that were domesticatedremained mostly uncommitted to the symbiosis until a single lineage became an obligate symbiont of a derived clade of these ants - the so called higherattines. Coevolution of ants and fungi has subsequently produced specific adaptations in both partners, including the development of special hyphal tips(gongylidia) of the fungus on which the ants feed. Recent work has shown that many fungal enzymes pass through the ant digestive system unharmed tobe mixed (as fecal fluid) with the fresh leaf pulp that the ants deposit on top of their gardens. To understand the function of this form of fungal enzymetransfer, we have used state of the art proteomics and high-throughput genome sequencing to identify the proteins found in the ant fecal fluid. Fecalproteins of Acromyrmex leafcutter ants were separated with SDS-PAGE followed by tandem mass spectrometry, and the resulting peptide tags were usedas queries to Blast-search a low coverage genome sequence of the fungal symbiont. Using this strategy we identified 34 protein sequences encoded by thefungal genome. Enzyme assays for selected fecal proteins showed that they functionally disappeared from the fecal droplets when the ants were deprivedof their fungal symbiont. We further used qPCR to establish that many of these proteins are more highly expressed in gongylidia than in mycelium,suggesting that they have been actively selected to be ingested by the ants. A substantial fraction of the fecal proteins are enzymes that are widely used byplant-pathogens to break down cell walls to access the easily degradable nutrients inside living cells. Of special interest is the finding of a polyphenoloxidizinglaccase enzyme that shows signs of positive selection in the higher attine ant symbionts, and may be an important prerequisite for the ability tocope with the polyphenols present in plant tissues. The results indicate that the leafcutter ants and their fungal symbionts have evolved traits-syndromesthat are partially convergent with those found in plant-pathogenic fungi.Unraveling the metabolome: how zombie ant fungi heterogeneously control ant brains. Charissa de Bekker, David Hughes. Biology and Entomology,Center for Infectious Disease Dynamics,Pennsylvania State University, State College, PA.Fungal entomopathogens rely on cellular heterogeneity during the different stages of insect host infection. Their pathogenicity is exhibited through thesecretion of secondary metabolites. Infection strategies of this group of environmentally important fungi can thus be studied by analyzing theirmetabolome. Next to generalists such as Beauveria bassiana and Metarhizium anisopliae, specialist species exist that are able to control host behavior.One of the most dramatic examples is the death grip of ants infected by Ophiocordyceps unilateralis, where ants are being used as a vehicle and finally biteinto vegetation before dying, aiding fungal spore dispersal after death. To establish this the fungus must not only overcome the immune system of thehost, but also manipulate the brain and atrophy the muscles. To date, most work on manipulation of host behavior has described the ant’s behavior,leaving the molecular processes from the fungal point of view unresolved. To start unraveling the mechanisms underlying this phenomenon we arecombining metabolite profiling with an ex vivo insect tissue culturing system that allows us to study fungal metabolites secreted in different parts withinthe host. Using this technique we established that B. bassiana and M. anisopliae, and O. unilateralis heterogeneously react to brain and muscle tissue bysecreting a significantly different array of metabolites. The combination of these approaches with a concrete understanding of the host-parasiteinteraction in nature is allowing us to understand both the diversity of secondary metabolites as well as make discoveries regarding the temporal dynamicsthese fungi employ when releasing metabolites that affect the host. This project is financed by the Marie Curie International Outgoing Fellowships andPenn State University .Trichoderma rhizosphere’s competency, endophytism and plant communication: A molecular approach. Artemio Mendoza 1 , Johanna Steyaert 1 , NataliaGuazzone 1 , Maria Fernanda Nieto-Jacobo 1 , Mark Braithwaite 1 , Robert Lawry 1 , Damian Bienkowski 1 , Christopher Brown 2 , Kirstin MacLean 1 , Robert Hill 1 ,Alison Stewart 1 . 1) Bio-Protection Research Centre, Lincoln University, Lincoln, New Zealand; 2) Biochemistry Department and Genetics Otago, Universityof Otago, New Zealand.Establishment of root symbiosis is one the key drivers of biocontrol success for members of the fungal genus Trichoderma. This root symbiosis isdescribed as a two-step process, whereby Trichoderma species colonise the soil surrounding the root (rhizosphere) and then penetrate the root tissue andestablish an endophytic relationship. The ability to colonise and then proliferate over time within the rhizosphere is termed rhizosphere competence (RC).There have been numerous reports of Trichoderma biocontrol strains which persist within the rhizosphere for the growing season of the crop plant. Ourresults strongly suggest that RC is widespread among members of the genus Trichoderma and that RC interactions are strain and host plant specific. Forendophytes and their host plants to maintain a mutualistic relationship requires a constant molecular dialogue between the organisms involved. Forexample, the fungal-derived phytohormone, indole acetic acid (IAA), plays an important role in signalling between Trichoderma and the model plantArabidopsis thaliana. There are however, additional, currently unknown, chemical signals which may be even more important for a positive interactionbetween Trichoderma and plants. By using a soil-maize-Trichoderma as a model system in in situ sterile conditions we are currently analysing the RC andendophytism transcriptomes of two Trichoderma species: T. virens and T. atroviride. Using a combination of bioinformatics, quantitative RT-PCR (for stagespecific genetic markers from Trichoderma) and fluoro-labelled Trichoderma strains we are currently identifying and analysing promising Trichodermacandidates involved in endophytism and RC. A comprehensive panorama of the Trichoderma-soil-plant interaction will be discussed in this conference.27th Fungal Genetics Conference | 33