Program Book - 27th Fungal Genetics Conference

FULL POSTER SESSION ABSTRACTSE.elymi x E. amarillans).609. The Interaction of Mycoplasma-related Endobacteria with their Arbuscular Mycorrhizal Fungal Host. Mizue Naito 1 , Teresa Pawlowska 2 . 1) Dept. ofMicrobiology, Cornell University, Ithaca, NY; 2) Dept. of Plant Pathology & Plant-Microbe Biology, Cornell University, Ithaca, NY.Arbuscular mycorrhizal fungi (AMF), comprising the monophyletic phylum Glomeromycota, are obligate biotrophs, and form symbiotic associations with80% of terrestrial plants. AMF associate symbiotically with the roots of plants, and are specialized in the transfer of nutrients from the soil to the planthost. In return for increased nutrient uptake, the plants supply AMF with up to 20% of their photosynthetically derived carbohydrates. Thus, AMFsymbiosis contributes significantly to global nutrient cycling and terrestrial ecosystems. AMF have been known to harbour two types of bacteria in theircytoplasm: (i) the Burkholderia-related Candidatus Glomeribacter gigasporarum and (ii) a Mycoplasma-related bacteria, which we refer to as Mycoplasmarelatedendobacteria (MRE). MRE live freely in the AMF cytoplasm, and have been found associated with all lineages of AMF worldwide. Virtually nothingis known about the MRE, such as their evolution, biological capabilities, and whether they are mutualists or parasites of their AMF hosts. In order tounderstand the nature of this symbiosis, and determine the role that the MRE play in arbuscular mycorrhizae, next generation sequencing (Roche 454 andIllumina) was performed on MRE isolated from 3 distinct AMF hosts, Claroideoglomus etunicatum, Funneliformis mosseae, and Racocetra verrucosa.Phylogenetic reconstruction and divergence dating using 22 conserved genes have revealed that MRE form a novel monophyletic subclade of theMycoplasmas and have diverged from their Mycoplasma relatives at least 400 million years ago, which may indicate the establishment of the MRE-AMFassociation to be quite ancient. Analysis of annotated genes have revealed novel proteins that are likely to play a role in interacting directly with the fungalhost. Preliminary data suggest that MRE are important in enabling the completion of the life cycle of their AMF hosts.610. The Velvet gene is required for mutualism between Epichloë festucae and perennial ryegrass. Mostafa Rahnama 1,2 , Richard Gardner 1 , DamienFleetwood 2 . 1) School of Biological Sciences, University of Auckland, Auckland, New Zealand; 2) Forage Improvement Group, AgResearch, Auckland, NewZealand.The velvet gene (veA or velA) is a key factor in the regulation of fungal development, biosynthesis of secondary metabolites and hyphal growth. Thisstudy aimed to determine the role of velA regulation in Epichloë festucae and its mutualistic interaction with the agriculturally important forage perennialryegrass (Lolium perenne). Infection of perennial ryegrass with an E. festucae mutant deleted in velA caused rapid seedling death in two thirds of infectedplants while remaining plants displayed a normal interaction phenotype, although after several weeks these plants also become stunted and died in anunusual delayed plant-interaction phenotype. No hypersensitive response was observed by microscopy, suggesting the response is not driven bypathogen-like effector proteins. Microscopic analysis showed different accumulation of polysaccharides between mutant and wild type strains. Themutant strain could grow in higher concentrations of calcolfluor and also there was different colony hydrophobicity between wild type and mutant strains.These different cell wall properties suggest a possible microbe associated molecular pattern (MAMP)-triggered defense response may be occurring inDvelA mutant associations. We are currently analysing the transcriptomes of wild type and mutant E. festucae/Lolium perenne symbiota to determine thevelA regulon and elucidate the mechanism of host death.611. An examination of phosphate solubilization and hormone production by two Penicillium species growing in the rhizoplane. Tim Repas 1,2 , DavidGreenshields 2 , Susan Kaminskyj 1 . 1) Department of Biology, University of Saskatchewan, Saskatoon, Saskatchewan, Canada; 2) Novozymes BioAg Ltd. 3935Thatcher Ave, Saskatoon, SK S7R1A3, Canada.Some soil microorganisms, including fungi, can enhance plant growth in the natural environment, however the mechanism(s) by which they promoteplant growth (PGP) are only partly known, and at any rate these will likely vary between organisms. Possible mechanisms for PGP include enhancednutrient uptake, hormone production, pathogen biocontrol, and increased water use efficiency. We are evaluating the potential of two rhizosphere fungi,Penicillium bilaiae (Pbil) and a novel isolate (Skj340) that is most closely related to Penicillium atramentosum. Both fungi can solubilize in liquid cultureeach of Fe-, Al-, and Ca-phosphates, which are commonly found in soil. Both strains were able to solubilize phosphate minerals equally well. However, Pbilproduces abundant organic acids, whereas Skj340 does not produce organic acids, nor even change the pH of the spent medium. Pbil has been tagged withred fluorescent protein (RFP); Skj340 has been stained with lactofuschin; both were imaged with confocal fluorescence. Both fungi are found on the rootsurface, and neither could be isolated from surface sterilized plants, thus it appears that these strains are not endophytic. We are currently evaluatingproduction of gibberellins and auxins from Pbil and Skj340 by assessing their ability to complement the phenotype of Arabidopsis mutants deficient inthese hormones. We will also assess whether either strain enhanced root hairs counts, which is expected to be correlated with both nutrient uptake andhormone activity.612. The role of Epichloe festucae RacA interacting proteins, PakA, PakB and RhoGDI, on cell polarity in culture and synchronized growth in Loliumperenne. Yvonne Becker, Carla Eaton, Isabelle Jourdain, Barry Scott. Institute of Molecular BioSciences, Massey University, Palmerston North, NewZealand.The fungal endophyte Epichloe festucae and its host Lolium perenne are an interesting model system to study signals and mechanisms involved inmutualistic symbiosis maintenance. Mutants defective in components of the ROS producing Nox complex show loss of synchronized growth of the fungusin the grass resulting in stunted, multi-tillered plants (Tanaka et al. 2006, Takemoto et al., 2006). The small GTPase RacA is crucial to activate the Noxcomplex in E. festucae and plays a crucial role in establishment and maintenance of polarized hyphal growth (Tanaka et al., 2008). The objectives of thisstudy were to determine whether key regulators of RacA in mammalian systems, the guanine nucleotide dissociation inhibitor (RhoGDI) and p21-activatedkinases (Paks), also regulate fungal RacA in order to control polarised growth in culture and Nox activity for maintenance of the symbiosis with perennialryegrass. We showed by yeast two-hybrid analysis that PakA (Cla4 homolog), PakB (Ste20 homolog) and RhoGDI interact with RacA, whereas the RhoGDIinteraction is compromised in a mutant of RacA (R73E) required for RhoGDI binding. Only partial complementation is achieved when RacA (R73E) isexpressed in the RacA deletion strain, indicating RhoGDI is important for controlling RacA function. Deletion of pakB had a mild effect on polarized hyphalgrowth in culture and wild-type growth in planta. Deletion of pakA had a severe effect on polarized hyphal growth in culture, with a reduction of radialgrowth and hyper-branching, a phenotype similar to the racA mutant but surprisingly plants infected with the pakA mutant had a wild-type interactionphenotype. The in planta results may reflect the fact that E. festucae grows by intercalary rather than tip growth in the intercellular spaces of perennialryegrass leaves.613. A Host-Induced Gene Silencing Approach to Control Mycotoxin Contamination in Corn. J. E. Smith, Y. B. Ramegowda, B. H. Bluhm. University ofArkansas, Fayetteville, AR.The fungal ear rot pathogens Aspergillus flavus and Fusarium verticillioides contaminate corn with aflatoxins and fumonisins, which pose severe health27th Fungal Genetics Conference | 271