Examining Arbuscular Mycorrhizal Fungi in Saltmarsh
Hay (Spartina patens) and Smooth Cordgrass (Spartina
alterniflora) in the Minas Basin, Nova Scotia
Tyler W. d’Entremont, Juan C. López-Gutiérrez, and Allison K. Walker. 2018. Northeastern Naturalist 25(1):72-86. saltmarsh AMF
ABSTRACT Saltmarshes are highly productive ecosystems that provide nursery and refuge habitat for animals, buffer storm-wave effects, and stabilize coastlines. Unfortunately, saltmarshes are in decline due to several cumulative stressors. Beneficial root-associated fungi are known to colonize >80% of land plants, but are understudied in intertidal zones. We examined arbuscular mycorrhizal fungi (AMF) in the roots of 2 dominant saltmarsh cordgrasses, Spartina patens (Saltmarsh Hay) and Spartina alterniflora (Smooth Cordgrass) (Poaceae), in the Minas Basin, NS, Canada. We collected 9 sediment cores at the beginning, middle, and end of the 2016 growing season (May–September) for each plant species (n = 54). We examined AMF root colonization using microscopy and fungal-DNA barcoding. Smooth Cordgrass had an AMF root colonization rate of 9%, while Saltmarsh Hay exhibited a higher AMF root colonization rate of 68%. We identified 1 AMF species, Funneliformis geosporum (Glomeraceae), in both host-plant species. We present the first Spartina spp. (cordgrasses) AMF root-colonization data for northeastern North America north of Connecticut, which may aid saltmarsh restoration efforts in Nova Scotia.
The homothallic mating-type locus of the conifer needle endophyte Phialocephala scopiformis DAOMC 229536 (order Helotiales)
Brent M. Robicheau, Adèle L. Bunbury-Blanchette, Kurt LaButti, Igor V. Grigoriev, Allison K. Walker. 2017. Fungal Biology. https://doi.org/10.1016/j.funbio.2017.08.007
ABSTRACT We describe the complete mating-type (MAT) locus for Phialocephala scopiformis Canadian Collection of Fungal Cultures (DAOMC) 229536 – a basal lineage within Vibrisseaceae. This strain is of interest due to its ability to produce the important antiinsectan rugulosin. We also provide some of the first insights into the genome structure and gene inventory of nonclavicipitalean endophytes. Sequence was obtained through shotgun sequencing of the entire P. scopiformis genome, and the MAT locus was then determined by comparing this genomic sequence to known MAT loci within the Phialocephala fortinii s.l.–Acephala applanata species complex. We also tested the relative levels of sequence conservation for MAT genes within Vibrisseaceae (n = 10), as well as within the Helotiales (n = 27). Our results: (1) show a homothallic gene arrangement for P. scopiformis [MAT1-1-1, MAT1-2-1, and MAT1-1-3 genes are present], (2) increase the genomic survey of homothallism within Vibrisseaceae, (3) confirm that P. scopiformis contains a unique S-adenosyl-l-methionine-dependent methyltransferase (SAM-Mtase) gene proximal to its MAT locus, while also lacking a cytoskeleton assembly control protein (sla2) gene, and (4) indicate that MAT1-1-1 is the more useful molecular marker amongst the MAT genes for phylogenetic reconstructions aimed at tracking evolutionary shifts in reproductive strategy and/or MAT loci gene composition within the Helotiales.
The complete mitochondrial genome of the conifer needle endophyte, Phialocephala scopiformis DAOMC 229536 confirms evolutionary division within the fungal Phialocephala fortinii s.l. – Acephala appalanata species complex
Full Genome of Phialocephala scopiformis DAOMC 229536, a Fungal Endophyte of Spruce Producing the Potent Anti-Insectan Compound Rugulosin
Antimicrobial dihydrobenzofurans and xanthenes from a foliar endophyte of Pinus strobus
Susan N Richardson, Tienabe K Nsiama, Allison K Walker, David R McMullin, J David Miller. 2015. Phytochemistry 117: 436-443.
ABSTRACT Foliar fungal endophytes of Pinus strobus (eastern white pine) were collected from different sites across south-eastern New Brunswick, Canada and screened for the production of bioactive metabolites. From one site, two fungal isolates representing a formerly unknown genus and species within the family Massarinaceae (Pleosporales, Dothideomycetes, Ascomycota) were resolved by phylogenetic analysis. These isolates produced crude organic extracts that were active against Microbotryum violaceum and Saccharomyces cerevisiae. From these strains, DAOM 242779 and 242780, four dihydrobenzofurans (1–4) and two xanthenes (5–6) were characterized. Structures were elucidated by HRMS, interpretation of NMR spectra and other spectroscopic techniques. All isolated metabolites displayed antimicrobial activity against the biotrophic fungal pathogen M. violaceum and Bacillus subtilis. Phytochem 2015
Distribution of the foliar fungal endophyte Phialocephala scopiformis and its toxin in the crown of a mature white spruce tree as revealed by chemical and qPCR analyses.
ABSTRACT Phialocephala scopiformis is a foliar fungal endophyte of white spruce that produces the anti-insect compound rugulosin and other compounds in lower amounts. Seedlings inoculated with this and other toxigenic endophytes have increased tolerance to the spruce budworm, Choristoneura fumiferana. The presence of rugulosin in the diet and in needles infected by P. scopiformis reduces the growth rate of the insect. One of 300 white spruce trees inoculated as a seedling in 2001 was chosen to investigate the distribution of P. scopiformis and its principal toxin rugulosin throughout the crown. To facilitate the detection of the fungus in small samples, a qPCR assay was developed based on the ITS region of fungal ribosomal DNA targeting a genetic polymorphism unique to P. scopiformis. The assay was specific, with a method limit of detection 100 ng mycelium/g needle sample with high reproducibility and accuracy. We found that 11 years after inoculation, P. scopiformis DAOM 229536 and its toxin were detectable in needle samples distributed throughout the crown. Of the 109 samples tested, 100% of the rugulosin-positive samples also tested positive for P. scopiformis DAOM 229536 DNA in the qPCR assay. The mean and median needle rugulosin concentrations were > 2 times that required to reduce the growth of spruce budworm.
Griseofulvin-producing Xylaria endophytes of Pinus strobus and Vaccinium angustifolium: evidence for a conifer-understory species endophyte ecology.
Susan N Richardson, Allison K Walker, Tienabe K Nsiama, Jordan McFarlane, Mark W Sumarah, Ashraf Ibrahim, J David Miller. 2014. Fungal Ecology 11:107-113. http://authors.elsevier.com/a/1PcwR_dv8-dfa2
ABSTRACT During three decades of research on conifer endophytes of the Acadian forest, numerous insights have been gained in conifer-fungal ecology and secondary metabolite production. Recently, we have explored endophyte assemblages of understory plants commonly occurring with pine. Here we report for the first time the production of the potent antifungal compound griseofulvin by a fungal endophyte isolated from eastern white pine (Pinus strobus) needles and lowbush blueberry (Vaccinium angustifolium) stems from the Acadian forest of New Brunswick and Nova Scotia, Canada. Maximum likelihood phylogenetic analysis has placed the endophyte strains as an undescribed Xylaria sp. Our study highlights the complexity of endophyte-host lifecycles and points to the existence of a pine-blueberry ecotype. Aside from griseofulvin, piliformic acid was isolated from one of the pine endophytes. This compound has been reported from Xylaria and related species but not from Penicillium species known to produce griseofulvin.
Ophiognomonia acadiensis. Fungal Planet 274.
Allison K. Walker, Yuuri Hirooka, Donald M. Walker. 2014. Persoonia – Molecular Phylogeny and Evolution of Fungi 32:290-291. Ophiognomonia acadiensis, species novo
Marine fungal diversity: a comparison of natural and created salt marshes of the north-central Gulf of Mexico.
Allison K Walker, Jinx Campbell. 2010. Mycologia 102(3):513-21. Marine fungi_GOM_saltmarshes
ABSTRACT Marine fungal communities of created salt marshes of differing ages were compared with those of two reference natural salt marshes. Marine fungi occurring on the lower 30 cm of salt marsh plants Spartina alterniflora and Juncus roemerianus were inventoried with morphological and molecular methods (ITS T-RFLP analysis) to determine fungal species richness, relative frequency of occurrence and ascomata density. The resulting profiles revealed similar fungal communities in natural salt marshes and created salt marshes 3 y old and older with a 1.5 y old created marsh showing less fungal colonization. A 26 y old created salt marsh consistently exhibited the highest fungal species richness. Ascomata density of the dominant fungal species on each host was significantly higher in natural marshes than in created marshes at all three sampling dates. This study indicates marine fungal saprotroph communities are present in these manmade coastal salt marshes as early as 1 y after marsh creation. The lower regions of both plant hosts were dominated by a small number of marine ascomycete species consistent with those species previously reported from salt marshes of the East Coast of the USA.
First records of the seagrass parasite Plasmodiophora diplantherae from the northcentral Gulf of Mexico
Allison K Walker, Jinx Campbell. 2009. Gulf and Caribbean Research 21:63-65. seagrass parasite
New Clavulina species from the Pakaraima Mountains of Guyana