Book of Abstracts (PDF) - International Mycological Association

IMC7 Monday August 12th Lectures
of mycotoxins is essential for risk assessment and will be
used in determining whether there may be a relationship
between observed adverse effects in humans and exposure
to a particular mycotoxin. In order to apply the control on
mycotoxins and to set standards for trading purposes, it is
necessary to have collaborative tested and validated
methods of anaylsis and sampling. The coherent approach
of how EU-wide standards will be established will be
addressed.
75 - Ink cap sex and mushroom development
U. Kües 1* , R.C. Bertossa 2 , A.P.F. Bottoli 2 , D. Ciardo 2 , P.-
H. Clergeot 2 , Yi Liu 2 , S. Loos 2 , G. Rupricht-Robert 2 , P.J.
Walser 2 , M. Künzler 2 & M. Aebi 2
1
Molecular Wood Biotechnology, Institute for Forest
Botany, Georg-August University Goettingen, Buesgenweg
2
2, D-37077 Goettingen, Germany. - Institute for
Microbiology, ETH Zurich, Schmelzbergstr. 7, CH-8092,
Switzerland. - E-mail: ukuees@gwdg.de
Sexual development in C. cinereus occurs on the dikaryon
under control of the mating type loci. A mating type
proteins, homeodomain transcription factors, induce
fruiting body initiation under appropriate light, temperature
and nutritional conditions. Development starts with intense
localized branching leading to a small loose structure
(primary hyphal knot). Light and A genes are needed to
transform it into a compact round aggregate (secondary
hyphal knot) in which cap and stipe tissues differentiate.
Once a primordium is fully established, light and the B
mating type proteins (pheromone and their receptors)
induce karyogamy and fruiting body maturation. Next to
studying nutritional signalling, we identified some genes
acting at the first steps in fruiting. One uncharacterised
gene acts in primary hyphal knot formation, gene cfs1 for a
potential cyclopropane fatty acid synthase in the transition
to secondary hyphal knots. Work in B. Lu's lab presented
us two galectin genes, whose first expression correlates
with formation of primary (cgl2) and secondary hyphal
knots (cgl1). Structural analysis within the fruiting body
suggests these protein to function in hyphal aggregation.
Due to control by A mating type proteins, light, C and N
sources, their promoters provide us with an ideal system to
identify cis- and trans-acting elements in transcriptional
regulation. Supported by the ETH Zurich, the Swiss
National Science Foundation and the Deutsche
Bundesstiftung Umwelt.
76 - How mushrooms work
N.P. Money
Department of Botany, Miami University, Oxford, Ohio
45056, U.S.A. - E-mail: moneynp@muohio.edu
With characteristic eccentricity, A. H. R. Buller (1931)
determined the weight-lifting capacity of Coprinus fruiting
bodies. From the mass raised by developing basidiocarps,
he estimated that hyphae elongating within the stipe
generated a pressure of 0.07 MPa (or two-thirds of an
atmosphere). When all of the fruiting bodies emerging in a
cluster exert pressure of this magnitude, their combined
force is sufficient to crack compacted soil or decaying
wood (and to dislodge paving slabs positioned over their
mycelia in urban areas). For example, a pressure of 0.07
MPa applied over an area of 0.01 square meters (= 10 × 10
cm), produces a total force of 700 N. This is sufficient to
lift the combined mass of the author of this presentation
plus all seven volumes of Buller's Researches on Fungi (=
71 kg). Interest in these classical experiments has been
revived by biomechanical research involving precise
measurement of the forces exerted by single hyphae. The
instrumentation used in these investigations is also
effective for studying the mechanical behavior of
multicellular fungal organs, and valuable information on
the origin and control of force during fruiting-body
emergence has been obtained during preliminary
experimentation. Once the mushroom has surfaced, a
variety of developmental adaptations optimize the
discharge of spores from the gills and dispersal in air
currents flowing beneath the cap. Recent work on
basidiocarp form and function is also featured in this
presentation.
77 - Forceful invasion of corn leaves
H.B. Deising * , S. Werner, J.A. Sugui & M. Wernitz
Martin-Luther-Universität Halle-Wittenberg,
Landwirtschaftliche Fakultät, Phytopathologie und
Pflanzenschutz, Ludwig-Wucherer-Str. 2, D-06099 Halle
(Saale), Germany. - E-mail: deising@landw.uni-halle.de
The corn pathogen Colletotrichum graminicola causes the
anthracnose disease of several cereals and grasses. To
infect the leaf, conidia germinate and differentiate a
specialized infection cell called an appressorium (Deising
et al. 2000). When an appressorium matures it accumulates
osmotically active compounds to yield high concentrations.
The resulting turgor pressure of more than 5 MPa is
translated into forces of up to 17 µN by single appressoria
(Bechinger et al. 1999; Bastmeyer et al. 2002). These
figures indicate the importance of the rigidity of the fungal
cell wall. We performed targeted inactivation of three
chitin synthase genes of the corn anthracnose fungus and
found that only CgCHSC is essential for vegetative growth
and pathogenic development. To analyze the role of cell
wall-degrading enzymes in the infection process we
generated mutants defective in CgSNF1, a gene involved in
activation of catabolite-repressed genes (Tonukari et al.
2000). Reduced growth rates on complex corn cell walls
and reduced rates of infection suggest that cell walldegrading
enzymes assist forceful invasion by C.
graminicola. Bastmeyer, M., Deising, H.B., Bechinger, C.
2002. Annu. Rev. Biophys. Biomol. Struc. 31:167-175
Bechinger, C., Giebel, K.-F., Schnell, M., Leiderer, P.,
Deising, H.B., Bastmeyer, M. 1999. Science 285:1896-
1899 Deising, H.B., Werner, S., Wernitz, M. 2000.
Microbes Infect. 2:1631-1641 Tonukari, N.J., Scott-Craig,
J.S., Walton, J.D. 2000. Plant Cell 12:237-248.
Book of Abstracts 25