Program Book - 27th Fungal Genetics Conference

FULL POSTER SESSION ABSTRACTSHaNLP3 protein and mount an effective immune response. Our research is now focused on determining how Arabidopsis is able to respond to the HaNLPsand how the downy mildew pathogen can suppress the host immune response triggered by non-toxic NLPs.597. Genes important for in vivo survival of the human pathogen Penicillium marneffei. Harshini C. Weerasinghe, Michael J. Payne, Hayley E. Bugeja,Alex Andrianopoulos. Genetics, The University of Melbourne, Parkville, Victoria, Australia.Pathogenic fungi are having an increasing global impact in the areas of health, agriculture and the environment. As such it is essential to understand themechanisms that fungi employ to survive and grow within a host. The emergence of many new “opportunistic fungal pathogens” has to a great extentaltered the traditional view that pathogenicity was solely reliant on the inherent properties of the pathogen. In fact, the ability of a pathogen to causedisease in some hosts but not in others suggests that pathogenic determinants are complex and dynamic, and are largely dependent on specific pathogenhostrelationships. Despite this there are conserved aspects of the interactions between host and pathogen. For example., hosts employ innate immuneresponses as an almost immediate recognition and attack mechanism against invading pathogens. Penicillium marneffei is a temperature dependentdimorphic fungus, growing in a hyphal form producing conidia at 25°C and as a yeast form at 37°C. Despite its importance as an opportunistic pathogen,little is known about the biology and mechanism of infection of P. marneffei. The infectious agents (conidia) are believed to be inhaled, reaching thealveoli of the lungs, where they are phagocytosed by alveolar macrophages for elimination. At this point that P. marneffei switches growth to a pathogenicyeast cell form, and is able to withstand macrophage cytotoxic attacks to cause infection. In order to understand how P. marneffei responds to the host,RNA-seq analysis was used to create a transcriptomic profile of P. marneffei, when infected in murine macrophages. These results were compared to RNAseqdata from hyphal (25°C) and yeast (37°C) cells grown in vitro in order to identify genes that are specifically upregulated during infection. Based on thisanalysis a group of genes of varying functions were chosen for gene deletion studies and tested for defects in pathogenicity. Among these is a group ofPep1-like aspartic endopeptidases which are a uniquely expanded family in P. marneffei and that show reduced virulence in a macrophage model.598. Oxalate-minus mutants of Sclerotinia sclerotiorum via T-DNA insertion accumulate fumarate in culture and retain pathogenicity on plants.Liangsheng Xu 1 , Meichun Xiang 1 , David White 1 , Weidong Chen 1,2 . 1) Plant Pathology, Washington State University, Pullman, WA; 2) USDA-ARS, WashingtonState University, Pullman, WA 99164.Sclerotinia sclerotiorum is a ubiquitous necrotrophic pathogen capable of infecting over 400 plant species including many economically important crops.Oxalic acid production has been shown in numerous studies to be a pathogenicity factor for S. sclerotiorum through several mechanisms. During ourrandom mutagenesis study of S. sclerotiorum using Agrobacterium-mediated transformation, we identified three mutants that had lost oxalate production.Southern hybridization blots showed the mutation was due to a single T-DNA insertion, and plasmid rescue and DNA sequencing confirmed that the T-DNAinsertion site was located in the ORF of oxaloacetate acetylhydrolase (Ssoah, SS1G_08218) of S. sclerotiorum. The mutants did not change the color of apH-indicating medium (PDA amended with 50 mg/L bromophenol blue). The pH values of 6-day PDB culture filtrates were 1.8-2.0 for the wild type and 2.8-3.1 for the mutants. No oxalic acid was detected using HPLC in culture filtrates or in the mycelium of the mutants, but another acid compound wasaccumulated in culture filtrates of the mutants and detected by HPLC, and the compound was identified as fumaric acid using LC-MS. The mutants showedreduced vegetative growth on PDA and produced sclerotia that are beige in color and soft in texture. Artificial acidic conditions (pH 3.4 and 4.2) enhancedvegetative growth and promoted normal (black and hard) sclerotial formation of the mutants. Furthermore, the oxalate-minus mutants retainedpathogenicity on pea, green bean and faba bean in detached leaf assays and on intact plants of Arabidopsis thaliana, and their virulence levels were similarto that of the wild type strain on certain host plants, but varied depending on the plant species tested. The mutant had increased expression levels of cellwall-degrading enzymes such as polygalacturonases compared to the wild type strain during the process of infecting pea leaves. The results showed that alow pH condition is very important for growth and virulence of S. sclerotiorum on its wide range of host.599. Molecular characterization of fungi associated with superficial blemishes of potato tubers in Al-Qasim region, Saudi Arabia. Rukaia M Gashgari 1 ,Youssuf A. Gherbawy 2 . 1) Biology Dept, King Abdulaziz university, Jeddah, Saudi Arabia; 2) Biology Dept, Taif university, Taif , Saudi Arabia.Potato (Solanum tuberosum) becoming a more and more important foodstuff in the world. Also, the visual quality of fresh potatoes became a dominantcriterion and a significative economical issue in potato market. According the vegetative reproduction of this species, requirements for visual quality arealso needed for potato tubers. As an organ for reserve and propagation, the tuber grows underground and is in contact with soil-borne microorganisms,making it potentially exposed to blemishes. Some blemishes are due to known pathogens and others whose causes are unknown are called atypicalblemishes. Therefore, knowledge about the pathogens is needed to set up efficient control strategies and to help potato growers to better know thecauses of these blemishes and find technical solutions for improving the potato quality. Therefore, the objective of this proposed research study is thepossibility of using some modern methods of molecular diagnostics and rapid detection of the presence of fungal contaminants in potato blemishes in Al-Qasim (Saudi Arabia). Polygonal lesions was the most observed blemish type in the collected samples. One hundred and sixty isolates were collected fromdifferent types of blemishes recorded in this study. Fusarium , Penicillium, Ilyonectria, Alternaria and Rhizoctonia were the most common genera collectedfrom different blemish types. Using ITS region sequencing all collected fungi identified the species level. All Fusarium strains colled during this study wereuse to detect its pathogenicity against potato tubers. The inoculated fungi were re-isolated from the diseased potato tubers to prove the Koch’spostulates. This is the first comprehensive report on identity of major pathogenic fungi causing potato dry rot isolated from potato tuber blemishes inSaudi Arabia.600. Patterns of Distribution of Bacterial Endosymbionts in Lower Fungi. Olga Lastovetsky 1 , Xiaotian Qin 2 , Stephen Mondo 2 , Teresa Pawlowska 2 , AndriiGryganskyi 3 . 1) Microbiology Dept, Cornell University, Ithaca, NY; 2) Plant Pathology & Plant-Microbe Biology Dept, Cornell University, Ithaca, NY; 3)Biology Dept, Duke University, Durham, NC.Fungi are not typically known to have endosymbionts. However, some members of Glomeromycota and Mucoromycotina have recently been found toharbor bacteria in their hyphae and spores. The newly discovered association between Rhizopus microsporus (Mucoromycotina) and Burkholderia bacteria(betaproteobacteria) prompted us to search for endobacteria in other members of Mucoromycotina fungi. We screened a broad range of Mucoromycotinaisolates for the presence of bacterial endosymbionts using PCR with universal and Burkholderia-specific primers that targeted the 16S and 23S rRNAbacterial genes. Endobacteria were only found in certain strains of R. microsporus but in no other Rhizopus or Mucoromycotina isolates. A 28S rRNA genephylogeny of the screened fungal isolates revealed a clustering of bacteria(+) R. microsporus isolates away from bacteria(-) R. microsporus isolates. Toexplore this putative divergence within the R. microsporus lineage we are working on a multi-gene phylogeny of Rhizopus isolates, which is based onmultiple coding and non-coding regions.268