Book of Abstracts (PDF) - International Mycological Association

IMC7 Thursday August 15th Lectures
expression polymorphism in E. festucae. Responses of two
aphid species (Rhopalosiphum padi and Schizaphis
graminum) to meadow fescue symbiota containing E.
festucae progeny segregating for LOL (Lol+ vs Lol-)
clearly implicate lolines as agents of protection against
insects. Successful map-based cloning has resulted in
identification of a >40kb gene cluster unique to the Lol+
parent. Subsequent sequencing of this region in E. festucae
(and related gene clusters in Neotyphodium uncinatum; see
poster by Spiering et al.) reveals relationships of the likely
loline alkaloid synthesis genes with fungal genes known
for synthesis of amino acids, polyamines and other
secondary metabolites.
312 - Inherent fitness advantage associated with
progression along the AF/ST polyketide biosynthesis
pathway in Aspergillus
H.H. Wilkinson 1* , A. Ramaswamy 1 , S.C. Sim 1 & N.P.
Keller 2
1 Texas A&M University, Department of Plant Pathology
and Microbiology 2132 TAMU College Station, Texas
77845-2132, U.S.A. - 2 University of Wisconsin, Department
of Plant Pathology, Madison, Wisconsin 53706, U.S.A. - Email:
heatherw@ppserver.tamu.edu
Sterigmatocytin (ST) is a polyketide-derived Aspergillus
mycotoxin and penultimate precursor of aflatoxin (AF).
Although the specific functions of many ST cluster genes
have been elucidated with regard to their role in the ST/AF
biosynthesis, the specific function of ST/AF for the fungi
that produce them is not known. We are attempting to
identify the fitness costs and/or benefits of ST expression.
Isogenic and prototrophic, A. nidulans mutants interrupted
at different genes in the ST biosynthesis cluster (delta-aflR,
delta-stcJ, delta-stcE, delta-stcU) and the wild type (ST)
were generated. These genotypes were grown on petri
plates containing glucose minimal media or on live.
Relative fitness was determined as a difference in the
number of conidia harvested after incubation for seven
days at 37°C.Two light conditions were used in these
fitness tests. In both experiments completing the ST
pathway was beneficial to fungal fitness. Rather than being
attributable to the impact of a knockout mutation, the tight
relationship between fitness ranking and position of each
gene product in the biochemical pathway support a direct
effect of these mutations on conidiation. These data suggest
that ST (and presumably AF) production contributes to the
fitness of Aspergillus under the environmental conditions
tested.
313 - Biology of secondary metabolites
J.D. Miller
Chemistry, Carleton University, Ottawa, Ontario K1S 5B6,
Canada. - E-mail: david_miller@carleton.ca
There are many perspectives on secondary metabolites of
the marine fungi, conifer endophytes and agricultural fungi
I have studied. The genes that code for secondary
metabolites seem largely to be clustered together implying
that their acquisition was not incremental but chaotic. Their
role in determining population structure focuses on the
benefit to species. Necrotrophic plant pathogens produce
virulence factors that also discourage the consumption of
the affected plant tissues by animals. Fungi that produce
toxins that affect animal competitors typically produce
several families of toxins. Some toxin families many be
more or less active against different potential herbivores.
Others result in additive toxicity with the important
consequence that acquisition of resistance to the toxin is
improbable. Despite this high degree of evolution, the
production of secondary metabolites by filamentous fungi
must first be thought of in terms of the biochemistry of the
terminal few cells of the mycelium. It has been known
since the invention of the microscope that it is only these
cells that are active, with of course the most active being
the hyphal tip. Control of the pathways of secondary
metabolism reflects the regulatory processes of glycolysis,
the citric acid cycle and electron transport. As nutrients
become unavailable to the active cells, accumulation of
acetate, citric acid cycle products and some amino acids
become available for the production of secondary
metabolites.
314 - Liard Hotsprings hypsothermal relict
commmunity: thermal impacts on fungi and plants in a
boreal forest ecosystem
R.S. Winder 1* , A. Ceska 2 & O. Ceska 2
1 Natural Resources Canada / Canadian Forest Service,
Pacific Forestry Centre, 506 W. Burnside Rd., Victoria,
B.C. V8Z 1M5, Canada. - 2 Botanical consultant, 1809
Penhurst Rd. Victoria, B.C. V8N 2N6, Canada. - E-mail:
rwinder@pfc.forestry.ca
The response of plants and fungi to temperature gradients
was studied in Liard Hot Springs Provincial Park in the
boreal forest of British Columbia. Within 50 m of the hot
springs, the forest was characterized by the proliferation of
understory shrubs such as bitter cherry (Prunus
emarginata) and bunchberry (Cornus canadensis), and
hardwood tree species such as balsam poplar (Populus
balsamifera) and paper birch (Betula papyrifera). By
contrast, the forest 150 m from the springs was occupied
primarily by white spruce (Picea glauca). Basal area of
tree stems declined with proximity to the springs and
increasing proportion of hardwoods; basal area 50 m from
the springs was half of the basal area 150 m from the
springs. Diversity of macrofungal fruiting bodies also
declined from an average of 33 species 150 m from the
springs, to an average of 13 species 50 m from the springs.
Fungi found in the warmer zones included species such as
Humaria hemispherica and Mycena delicatula.
Hygrophorus spp., Marasmius spp., and others were found
in the colder zones, while Cortinarius spp., Inocybe spp.,
and others were found throughout the gradients. Plant
diversity and the proportion of mycorrhizal species were
unchanged with respect to distance from the springs. While
Book of Abstracts 99