Program Book - 27th Fungal Genetics Conference

FULL POSTER SESSION ABSTRACTSfresh water environments.515. The Plant-Microbe Interfaces project: defining and understanding relationships between Populus and the rhizosphere microbiome. ChristopherSchadt 1 , Dale Pelletier 1 , Timothy Tschaplinski 1 , Edward Uberbacher 1 , Hurst Gregory 2 , E. Peter Greenberg 3 , Caroline Harwood 3 , Amy Schaefer 3 , RytasVilgalys 4 , Francis Martin 5 , Mitchel Doktycz 1 , Gerald Tuskan 1 , and other PMI researchers (http://pmi.ornl.gov). 1) Bioscience Division, Oak Ridge NationalLaboratory, Oak Ridge, TN, USA; 2) Chemical Sciences Division, Oak Ridge National Laboratory, Oak Ridge, TN, USA; 3) Department of Microbiology,University of Washington, Seattle, WA, USA; 4) Department of Biology, Duke University, Durham, NC, USA; 5) Institut National de la RechercheAgronomique, Nancy, FRANCE.Microbial interactions benefit plant health by affecting nutrient uptake, hormone signaling, water and element cycling in the rhizosphere and/orconferring resistance to pathogens. The model tree species Populus provides an opportunity for microbiome research relevant to bioenergy, carbon-cycleresearch, and other ecosystem processes. In an effort to define Populus’ microbiome, root and rhizosphere samples from P. deltoides in the eastern USand P. trichocarpa in western US were subjected rRNA pyrosequencing and an isolate collection of over 5000 bacteria and 500 fungi obtained. We showthat the rhizo- and endo-sphere environments feature highly developed, diverse and to a large degree often exclusive communities of bacteria and fungi.Endophytic bacterial diversity was found to be highly variable, but on average tenfold lower than the rhizosphere, suggesting root tissues provide a distinctenvironment supporting relatively few species. Fungal endophytic species were more numerous, but also less than rhizosphere spp. Both fungal andbacterial rhizosphere samples showed distinct phylogenetic composition patterns compared to the more variable endophyte samples. Contrary to initialexpectations, both Populus spp. have low natural levels of colonization by ectomycorrhizal (ECM) and arbuscular mycorrhizal fungi, but high levels ofpresumed fungal endophytic taxa such as Nectria, Mortierrella, and members of the Atractiellales. Select isolates are being studied at a whole-genomelevel to enable comparative work on on the basis for observed symbioses. Thus far ~43 bacterial and 5 fungal isolates have been sequenced. Initialcomparative genomics of these isolates suggest highly divergent physiological and molecular mechanisms of the interactions, even within rather closelyrelated species. Efforts to understand ECM interactions have shown that host defense networks and the ability to bypass such networks through smallprotein and phytohormone signals has a large effect on the ability of Populus to form ECM relationships. Laccaria bicolor is able to modulate host defenseresponse in P. trichocarpa, yet unable to do so in P. deltoides. Mycorrhizal Helper Bacteria from the genus Pseudomonas partially alleviate this colonizationweakness through yet unknown molecular mechanisms, illustrating the value of integrated microbiome wide studies.516. Do the fungal homologs of Verticillium dahliae effector Ave1 act as virulence factors? Jordi C. Boshoven 1 , Melvin D. Bolton 2 , Bart P.H.J. Thomma 1 . 1)Laboratory of Phytopathology, Wageningen University, 6708 PB Wageningen, Netherlands; 2) Agricultural Research Service, Northern Crop ScienceLaboratory, US Department of Agriculture, Fargo, ND 58102.Verticillium species cause vascular wilt disease in over 200 plant hosts, including economically important crops. In tomato, the Ve1 immune receptorconfers resistance to race 1 strains of V. dahliae, but not to race 2. By population genome sequencing of race 1 and race 2 strains, the effector that isrecognized by Ve1 was recently identified as Ave1 (Avirulence on Ve1 tomato). Ave1 has homology to plant natriuretic peptides that are regulators ofhomeostasis, and acts as a virulence factor on tomato plants that lack Ve1 as well as on Arabidopsis. In addition to plants, Ave1 homologs were also foundin a few fungal pathogens, including Fusarium oxysporum, Cercospora beticola and Colletotrichum higginsianum, as well as in the bacterial plant pathogenXanthomonas axonopodis. Co-expression of V. dahliae Ave1 and tomato Ve1 in Nicotiana tabacum resulted in the activation of a hypersensitive response.Remarkably, also co-expression of some of the Ave1 homologs with Ve1 activated a hypersensitive response. Here, we evaluate whether the variouspathogen-derived Ave1 homologs are virulence factors. Expression of the Ave1 homologs of Fusarium, Cercospora and Colletotrichum during infection ontomato, sugarbeet, and Arabidopsis, respectively, was analysed. To investigate the potential role of the Ave1 homologs in virulence, a V. dahliae Ave1deletion mutant was complemented with the Ave1 homologs of Fusarium, Cercospora and Colletotrichum, and tested for full aggressiveness on tomato.Finally, targeted gene deletion was pursued in Fusarium, Cercospora and Colletotrichum and the corresponding deletion strains were inoculated ontomato, sugarbeet, and Arabidopsis, respectively.517. The candidate effector repertoire of closely related Venturia pathogens of the Maloideae revealed by whole genome sequence and RNAsequencing analyses. Cecilia Deng 1 , Daniel Jones 2 , Bruno Le Cam 3 , Kim Plummer 2 , Carl Mesarich 4 , Matthew Templeton 1 , Joanna Bowen 1 . 1) Plant & FoodResearch, Auckland, New Zealand; 2) La Trobe University, Melbourne, Australia; 3) IRHS, INRA Angers, France; 4) Wageningen University, The Netherlands.The genus Venturia includes pathogens that infect members of the Rosaceae. The most widely researched of these is V. inaequalis that causes thedisease apple scab. Related species cause disease of other woody hosts closely related to Malus; eg V. pirina infects European pear. Certain isolates thatare classified as V. inaequalis are unable to infect Malus but instead infect different hosts belonging to the subfamily Maloideae, such as loquat. Hostcultivarspecificity is also demonstrated by isolates of V. inaequalis that infect Malus; 17 gene-for-gene pairings between effectors (pathogen proteins thatenhance disease) and resistance gene products have been identified to date. Thus the effector repertoire of isolates of V. inaequalis determines theircultivar specificity and most probably host specificity. Effectors have yet to be cloned from V. inaequalis. Draft whole genome sequences (WGS) of three V.inaequalis isolates (two from apple, one from loquat) and an isolate of V. pirina have been assembled and candidates that share the characteristics offungal effectors (small, secreted proteins) have been identified. Of the 13333 predicted genes in the WGS of V. inaequalis isolated from apple, 1088encode putatively secreted proteins identified utilising algorithms to detect secretion signals and putative cellular location. The expression (measured bytranscriptome analysis) of 119 of these is up-regulated, with a false discovery rate less than 0.05 and a log-fold change greater than 2, in planta comparedwith in vitro at both 2 and 7 days post inoculation (dpi), 73 at 2 dpi, and 54 at 7 dpi. Of these 246, only 43 have similarities (