Book of Abstracts (PDF) - International Mycological Association

IMC7 Monday August 12th Lectures
84 - Mycorrhization of endangered wetland plant
species
B. Fuchs 1 & K. Haselwandter 2*
1 University of Salzburg, Department of Botany,
Hellbrunnerstrasse 34, A-5020 Salzburg, Austria. -
2 University of Innsbruck, Department of Microbiology,
Technikersrasse 25, A-6020 Innsbruck, Austria. - E-mail:
Kurt.Haselwandter@uibk.ac.at
Arbuscular mycorrhizal (AM) fungal diversity in soil
seems to influence plant biodiversity. As information
concerning the mycorrhization of endangered plants is
lacking, we determined the mycorrhizal status of Serratula
tinctoria (Asteraceae), Betonica officinalis (Lamiaceae),
Drosera intermedia (Droseraceae) and Lycopodiella
inundata (Lycopodiaceae), occurring at two different sites
(bog and fen meadow) in the county of Salzburg, Austria.
In addition to AM fungi, infection by dark septate
endophytes (DSE) was quantified. The infection intensity
of AM fungi and DSE appeared to be higher in the fen
meadow than in the peat bog. The roots of S. tinctoria and
B. officinalis were heavily infected by AM fungi and both,
vesicles as well as arbuscules were observed over the
vegetation period. L. inundata showed AM fungal
infection, too; in spring vesicles were observed frequently,
in autumn they were less numerous. In D. intermedia roots
AM fungal infection intensity was lower than in the species
mentioned before; however, fungal structures typical for
AM fungal infection were observed, especially in spring. S.
tinctoria and B. officinalis were heavily infected by DSE,
while L. inundata was just slightly infected and D.
intermedia did not seem to be infected by DSE at all.
85 - Molecular genetics of gibberellin biosynthesis in
Gibberella fujikuroi
B. Tudzynski * & M. Mihlan
Universität Münster, Institut für Botanik, Schlossgarten 3,
48149 Münster, Germany. - E-mail:
bettina.tudzynski@uni-muenster.de
As well as being phytohormones, gibberellins (GAs) are
present in some fungi and bacteria. GAs were first
discovered in the fungus Gibberella fujikuroi, from which
gibberellic acid (GA3) and other GAs are produced
commercially. Although higher plants and the fungus
produce identical GAs, important differences in the
pathways and enzymes used have become apparent with
the identification of the genes for GA-biosynthesis in
Arabidopsis thaliana and G. fujikuroi. These profound
differences indicate that higher plants and fungi have
evolved the complex biosynthetic pathways to GAs
separately and not by horizontal gene transfer. In G.
fujikuroi, the 7 genes of the gibberellin (GA)-biosynthetic
path-way including four cytochrome P450 monooxygenases,
are located in a gene cluster. To study the function
of several genes of this cluster, we used a gene replacement
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Book of Abstracts
approach followed by GC-MS and HPLC analysis. Most of
the genes encode multifunctional enzymes. The availability
of the genes allows the study of molecular mechanisms of
gene regulation. Because the GA biosynthesis is regulated
by nitrogen metabolite repression, we cloned several genes
which are involved in nitrogen regulation, such as the
general nitrogen regulators, areA and nmr. Gene
replacement of areA led to a significant reduction of
gibberellin formation by repressing the expression of the
GA-pathway genes. In contrast, NMR does not play the
role as a general counterpart of AREA as expected.
86 - Involvement of ethylene in a plant - Botrytis cinerea
interaction
Y. Elad * , Z. Lapsker, I. Kolesnik, N. Korolev & B.
Kirshner
Dept. of Plant Pathology, The Volcani Center, P. O. B. 6,
Bet Dagan 50250, Israel. - E-mail:
elady@volcani.agri.gov.il
The role of ethylene was studied in the interaction of B.
cinerea with the host plants tomato, French bean and
Arabidopsis thaliana. Infected resistant Arabidopsis
produce less ethylene as compared with infected sensitive
plants. Ethylene promotes the disease development
whereas inhibition of plant ethylene production resulted in
disease suppression. Increased plant tissue reactive oxygen
species (ROS) levels resulted in elevated ethylene and
severe disease. The actual contact with pathogen cells (e.g.
dead conidia) induced ethylene and ROS in plants. This
effect was also obtained by leaf injury, H2O 2, pH reduction,
oxalic acid and botrydial; the compounds and effects are
produced by the pathogen. Antioxidants reduced ethylene
production and disease severity. Interestingly, ethylene
promoted conidia germination and subsequent penetration
to the host. Ethylene signaling mutants of Arabidopsis
showed extremely high susceptibility to B. cinerea; it is
possible that the pathway that leads to susceptibility is
independent of other ethylene signal transduction pathway.
B. cinerea has the potential to produce ethylene, thus it is
possible that the ethylene originates not only from the
plant. In conclusion, in B. cinerea - plants interaction
ethylene induces auto-catalytic production of the same
hormone in exposed tissues thus promoting the
deterioration of the infected tissue and the ROS
development and vice versa.
87 - Abscisic acid biosynthesis genes in Botrytis cinerea
V. Siewers * & P. Tudzynski
Institut fuer Botanik, Westf.Wilhelms Universitaet, D-
48149 Muenster, Germany.
Botrytis cinerea causes the grey mould disease in more
than 200 plant species. Like several other phytopathogenic
fungi, B. cinerea has been shown to produce different kinds