Book of Abstracts (PDF) - International Mycological Association

IMC7 Main Congress Theme V: CELL BIOLOGY AND PHYSIOLOGY Posters
months growth in sandy loam pot culture in greenhouse
condition inoculated at the seedling stage with the fungi
Glomus mosseae (Nicol. & Gerd.) Gerd. and Trappe or
Glomus interaradices Schenck & Smith, or uninoculated.
During the drought period and after rewatering, leaf water
potential, CO2 assimilation rate, stomatal conductance and
transpiration of plants were measured. Leaf water potential,
CO2 assimilation rate and stomatal conductance in
mycorrhizal plants during the unwatered period were, in
most cases, significantly greater than in the nonmycorrhizal
plants, particularly in those infected by G.
interaradices. There was no significant mycorrhizal effect
on transpiration rate. Mycorrhizal plants were able to
postpone the onset of wilting. During recovery from
drought, there were significant differences in speed of
recovery of leaf water potential, transpiration rate and
stomatal conductance in mycorrhizal plants, but not in
assimilation rate. Leaf areas and dry weight of mycorrhizal
plants were generally greater than non-mycorrhizal plants
after drought and recovery from drought.
1070 - Lignocellulose degradation by Pleurotus ostreatus
in the presence of heavy metals
P. Baldrian * & J. Gabriel
Institute of Microbiology AS CR, Videnska 1083, CZ-
14220, Prague 4, Czech Republic. - E-mail:
baldrian@biomed.cas.cz
The ability of white-rot fungi to decompose lignin,
cellulose, hemicelluloses and a range of structurally related
compound including several xenobiotics has found several
technological applications. The contents of heavy metals is
among the most important factors that affect the
lignocellulose-decomposing system of these fungi. In
Pleurotus ostreatus, Cu and Cd increase laccase activity,
whereas other metals (Hg, Pb, Ag, Zn) have negative effect
on enzyme production. Mn-peroxidase is negatively
affected by the presence of Cd. Heavy metals also affect
the carbon and energy-supplying system of
polysaccharides-decomposing enzymes. Addition of Cd to
P. ostreatus cultures increased the activities of
endocellulase, exocellulase, and β-1,4-glucosidase,
whereas β-1,4-xylosidase and β-1,4-mannosidase activity
was negatively affected. During cultivation of wheat straw,
the presence of Cd also decreased the substrate utilisation
(weight loss). Furthermore, some heavy metals, e.g. Cd and
Hg negatively affect fungal colonisation of both
lignocellulose substrate and nonsterile soil at low
concentrations, that do not affect the activity of ligninolytic
enzymes. This has to be taken into account when
applications of white-rot fungi for degradation of
xenobiotic contaminants in soil are considered, since these
processes are dependent upon external substrate input and
effective spread of mycelia in the substrate. This work was
supported by the Grant Agency of the Czech Republic
(204/02/P100).
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Book of Abstracts
1071 - High rates of extracellular superoxide
production by lichens in the suborder Peltigerineae
R.P. Beckett 1* , F.V. Minibayeva 2 & T. Tolpysheva 3
1 School of Botany and Zoology, University of Natal, PBag
X01, Scottsville 3209, South Africa. - 2 Institute of
Biochemistry and Biophysics, Russian Academy of Science,
PO Box 30, Kazan 420503, Russia. - Department of
Mycology, Moscow State University, Vorobjevi Gory,
Moscow 119899, Russia. - E-mail: beckett@nu.ac.za
Rates of extracellular superoxide radical formation were
measured in 34 species of lichens from different taxonomic
groupings and contrasting habitats before and after
desiccation stress. All 20 species tested from the suborder
Peltigerineae produce superoxide extracellularly at high
rates, even when they are not stressed. In addition, some
species show a burst of superoxide production during
rehydration following desiccation. In general, production
of high levels of superoxide and the existence of an
inducible oxidative burst were best developed in species
growing in wet microhabitats. Extracellular production of
superoxide was almost absent from the 14 species from
other lichen groups. Preliminary studies on the identity of
the superoxide producing enzymes suggested that they do
not possess the classical characteristics of those suggested
to produce reactive oxygen species in higher plants.
Patterns of superoxide production are discussed in terms of
their possible role as a defence against pathogenic fungi
and bacteria.
1072 - Cross talk between cAMP and calcium signalling
in the filamentous fungus Aspergillus niger
M. Bencina 1 , O. Kozlova-Zwinderman 2 , M. Legisa 1 &
N.D. Read 2*
1 Laboratory for Biotechnology and Industrial Mycology,
National Insitute of Chemistry, Hajdrihova 19, SI-1000
Ljubljana, Slovenia. - 2 Fungal Cell Biology Group,
Institute of Cell and Molecular Biology, University of
Edinburgh, Rutherford Building, Edinburgh EH9 3JH,
U.K. - E-mail: Nick@fungalcell.org
Very little is known about cross-talk between cAMP and
calcium signalling in filamentous fungi. The aim of this
study was to analyse the influence of cAMP and protein
kinase A (PKA)-dependent phosphorylation on calcium
signalling in Aspergillus niger. For this purpose, cytosolic
free calcium was measured in living hyphae expressing
codon-optimised aequorin whilst applying pharmacological
agents which increased cAMP levels or inhibited
phosphorylation by cAMP-dependent PKA. Calcium was
also measured in mutant strains in which phosphorylation
by PKA was increased or lacking. Our results indicate that
cAMP-dependent phosphorylation regulates calcium
homeostasis in A. niger, probably by activating calcium
channels. Further evidence for cross-talk between cAMP
and calcium signalling came from the analysis of a mutant
in which the catalytic subunit of PKA was under the
control of an inducible promoter. The consequence of PKA
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