Inoculum 63(3) - Mycological Society of America

In the famous last paragraph of the Origin, Darwin states, “There is
grandeur in this view of life...that...from so simple a beginning endless forms most
beautiful and most wonderful have been, and are being, evolved.” From this, in
part, comes the hard to shake idea that the progenitors of lineages were both primitive
and simple. By definition, the characters of the ancestor of a lineage are primitive.
However, many aspects of an ancestor, even a deep ancestor, were very
complex, not simple at all. The last common ancestor of living eukaryotes was a
sexual organism that had to have had a flagellate stage in its life cycle. These characters
had to have been true of the first opisthokont, and it was certainly more
complex than many members of the extant opisthokonts. Rather than worry about
whole organisms, perhaps it is better to compare sets of characters that we can hypothesize
result from share ancestry. For instance, multicellularity has arisen numerous
times in eukaryotes. In opisthokonts, multicellularity that includes cell migration
has arisen at least three times, at least once in Holozoa (Metazoa), and at
least twice in Nucletmycea (the sorocarpic Fonticula and the dikaryomycetes).
Do the seeds for using cell migration in multicellular development come from
characters of the last common ancestor of the extant opisthokonts? We do not yet
know, but if we learn to “think outside the box” as comparative biologists, it will
become easier to recognize those characters that need to be compared and to develop
a set of model organisms and that allow hypotheses to be tested.
Stajich, Jason E 1 , David A Hewitt 2 , and Gregory Jedd 3 . 1 Plant Pathology and
Microbiology, University of California, Riverside, CA USA, 2 Department of
Botany,
3
Academy of Natural Sciences of Philadelphia, Philadelphia, PA,
Temasek Life Sciences Laboratory and Department of Biological Sciences, The
National University of Singapore, Singapore. Insights into independent origins
of multicellularity in Neolecta from comparative genomics
The evolution of multicellular tissues in fungi, from the most fundamental
aspects of hyphal growth to development of complex fruiting bodies, required
a host of changes in cellular biology of fungi. Genome sequence comparisons provide
a means to study the molecular evolutionary changes across species through
the inventories of gene content and genome organization. Phylogenomic comparison
of genes in the filamentous Pezizomycotina fungi reveals a collection of lineage
specific genes including some known to be important for the filamentous
lifestyle such as the Hex proteins of Woronin body organelles, which are necessary
for septal pore plugging after hyphal wounding. Neolecta, a Taphrinamycotina
fungus, is phylogenetically distinct from the Pezizomycotina and may represent
an independent lineage where hyphal growth and complex fruiting bodies
evolved. By sequencing and comparing the genome of Neolecta irregularis to the
rest of the Ascomycete fungi we have found further evidence that filamentousspecific
genes in Pezizomycotina remain specific to the clade. Microscopy reveals
Wornin-body like structures in the hyphae of Neolecta, yet Woronin body genes
hex, wsc, leashin and spa9 are not found, suggesting independent origins for this
adaptation. The NADPH oxidases appear to be expressed in all multicellular fruiting
bodies, and one of these is encoded in the Neolecta genome, suggesting shared
traits that might have been present in a complex Dikarya ancestor. These and ongoing
analyses will reveal further patterns of genome evolution that link cell biology
changes to evolutionary transitions between unicellular and multicellular
forms in fungal history.
Sthultz, Christopher M 1 , Linda TA Van Diepen 2 , Serita D Frey 2 , and Anne
Pringle 1 . 1 Organismic & Evolutionary Biology Harvard University 16 Divinity
Avenue Cambridge, MA 02138, 2 Department of Natural Resources and the Environment
University of New Hampshire 56 College Road James Hall Durham,
NH 03801. Influences of nitrogen deposition and soil warming on saprophytic
fungal community structure, fungal growth, and litter decomposition
Impacts of global change on microbial communities remain poorly understood.
However, because microbes are important drivers of biogeochemical
cycles, anthropogenically mediated changes may have strong influences on
ecosystem function. Saprophytic fungi are primarily responsible for decomposition
in temperate forest systems, yet relatively little is known about whether global
changes, including nitrogen deposition and soil warming, will alter community
assembly processes. Here we focus on results from the first year of a multi-year
litterbag/decomposition experiment using long-term experimental N addition
(control, low and high N treatments) and soil warming plots (control and elevated
5 o C treatments) in a northeastern hardwood forest. We examined saprophytic
fungal community structure, fungal growth, and decomposition from 95 litter
bags harvested after 1 year in the field. Using metagenomics, culturing, and laboratory
microcosms we tested the influence of nitrogen deposition and soil warming
on fungal communities and ecosystem function. We document four major patterns:
1) Fungal communities in elevated nitrogen deposition and soil warming
plots were different from control plots. 2) Decomposition varied between treatment
and control plots in both experiments. 3) In the nitrogen experiment fungal
community composition and decomposition were influenced not only by treatment
but also by the source of the litter in the bags (from control, low, or high N
plots). There was a significant interaction effect on the community composition.
46 Inoculum 63(3), June 2012
4) There were differences in growth rates of the same fungal species cultured from
each of the three nitrogen treatments. Our results increase understanding of the
ecology and evolution of saprophytic fungi in a global change context, and add to
what is known about the biodiversity of decomposer fungi. In addition, our results
suggest global change may influence the fungi found in the environment, but also
the evolution of some fungal species.
Sweeney, Katarina, Michael Freitag, and Jeffrey Stone. Oregon State University,
Department of Botany and Plant Pathology, 2082 Cordley Hall, Corvallis, OR
97331-2902. Estimating genetic diversity of Cronartium ribicola populations
in Oregon by RAD marker genotyping
The pathogen, Cronartium ribicola, was introduced to North America in
1910 and found in SW British Columbia and NW Washington by 1922. Evidence
of evolutionary change in North American C. ribicola since its introduction is apparent
and spread of two virulent races pathogenic to WPBR-resistant genotypes
of Pinus monticola and P. lambertiana have been observed. The C. ribicola vcr1
race is virulent to P. lambertiana carrying a major gene (Cr1) that confers resistance
to “wild-type” C. ribicola and was first found in California in 1978. The vcr2
race is virulent to P. monticola carrying Cr2 that also confers resistance to “wildtype”
C. ribicola, and was found in Oregon in the early 1970s. Neither vcr1 or
vcr2 races are virulent to the resistant genotypes of the other species. Few studies
have been completed to estimate the genetic diversity of natural populations of C.
ribicola in western North America, but accurate characterization of host phenotypes
in resistance breeding programs requires more detailed understanding of the
diversity of C. ribicola populations. Resistance screening is carried out with wild
populations known to be predominantly vcr1, vcr2, or “wild-type” C. ribicola. In
order to gain a more precise understanding of the molecular basis of natural variation
in wild-type strains of C. ribicola in Oregon, we are employing restriction
site associated DNA (RAD) marker genotyping of C. ribicola aeciospores. RAD
sequencing generates short sequence reads adjacent to restriction enzyme sites
that serve to identify restriction polymorphisms between samples or can be used
to identify the presence of SNPs. We are using aeciospore samples from multiple
locations in Oregon. RAD mapping will allow us to relate the variation seen in
pine host reactions to infection by C. ribicola with informative SNPs in the
pathogen.
Sylvain, Iman A and Timothy Y James. University of Michigan, Department of
Ecology and Evolutionary Biology. 830 North University Ann Arbor, MI 48109.
Global population genetic structure of Aspergillus niger and Eurotium
rubrum in green coffee beans
Whether small species are ubiquitous and cosmopolitan remains a significant
question in mycological research. Whether “everything is everywhere,” and
how habitat properties or historical contingency influence the distribution of fungi
has yet to be fully understood. Determining species ranges for fungi can be challenged
by reliance on morphological characters for the identification of species,
and enlisting molecular techniques has shown that fungi may have varied ranges
that scale from largely global to narrowly endemic. Fungi associated with highly
mobile agricultural products may have global distributions that mirror the trade of
their plant hosts, or show patterns of biogeographic structure influenced by the
ecology of distinct agroecosystems. Trans-global gene flow in fungi may be facilitated
by the movement of agricultural commodities, resulting in panmictic
populations, and the observation that fungi show no correspondence between genetic
and geographic ranges. We are developing global coffee agriculture as a
model system to understand how the movement of food products influences the
dispersal of fungi. We have used a multi-locus sequencing technique to analyze
the population structure of two mycotoxigenic Aspergillus species, A. niger and
Eurotium rubrum, cultured from green coffee beans. Coffee beans were sourced
from eight countries: Kenya, Ethiopia, Mexico, Costa Rica, Guatemala, Papa
New Guinea, Bali, and Sumatra. The coffee was either produced as USDA-certified
organic, or by conventional agricultural methods, and either wet or dryprocessed.
Phylogenetic trees constructed from rRNA ITS sequences suggest that
multiple distinct, possibly cryptic species are present within the sampled A. niger
and E. rubrum clades. Beta-tubulin and calmodulin sequences show no geographic
structure in these species, suggesting that Aspergillus species associated
with coffee production may truly be everywhere.
Taerum, Stephen 1 , Z Wilhelm de Beer 2 , Tuan A Duong 1 , Min Lu 3 , Nancy
Gilette 4 , Jianghua Sun 3 , and Michael J Wingfield 1 . 1 Department of Genetics,
Forestry and Agricultural Biotechnology Institute (FABI), University of Pretoria,
Pretoria 002, South Africa, 2 Department of Microbiology and Plant Pathology,
Forestry and Agricultural Biotechnology Institute (FABI), University of Pretoria,
Pretoria 002, South Africa, 3 State Key Laboratory of Integrated Management of
Pest Insects and Rodents, Institute of Zoology, Chinese Academy of Sciences,
Beijing 100101, P. R. China, 4 Ecosystem Function and Health, PSW Research
Station, 800 Buchanan Street, Albany, CA 94710. Fungal symbionts suggest an
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