Book of Abstracts (PDF) - International Mycological Association

IMC7 Thursday August 15th Lectures
331 - A zinc tolerant ectomycorrhizal fungus protects
zinc-stressed pine seedlings
K. Adriaensen * , J. Vangronsveld & J.V. Colpaert
Limburgs Universitair Centrum, Laboratory of
Environmental Biology, Universitaire campus, 3590
Diepenbeek, Belgium. - E-mail:
kristin.adriaensen@luc.ac.be
The effect of sublethal zinc concentrations on pines
mycorrhizal with either a Zn-adapted or a Zn-sensitive
Suillus bovinus isolate was studied. A dose response
experiment was performed. During the zinc treatments the
nutrient uptake capacity (NH4 + and P i) was measured in a
semi-hydroponic environment. The Zn sensitive plantfungus
combination already failed to sustain nutrient
acquisition of the pines at 38 µM Zn. While nutrient uptake
in plants inoculated with the Zn tolerant S. bovinus was not
affected when exposed to the same Zn levels. Subsequently
plants mycorrhizal with the tolerant isolate captured more
Pi and were less iron deficient as plants mycorrhizal with
the sensitive fungus. Plant biomass was not yet affected,
but excess Zn significantly reduced the biomass of the Zn
sensitive fungus. These results show that the genetic
adaptation for increased Zn tolerance in Suillus bovinus is
required for its own survival and to maintain nutrient
acquisition in pines exposed to high Zn concentrations.
332 - Arbuscular mycorrhizal fungi and stress by heavy
metals and salts
H. Bothe * , U. Hildebrandt & F. Ouziad
Botanical Institute, University of Cologne, D-50923 Koeln,
Germany. - E-mail: hermann.bothe@uni-koeln.de
Plants from heavy metal soils can be colonized by
arbuscular mycorrhizal fungi. A Glomus intraradices
isolate has been obtained from the roots of the zinc violet,
Viola calaminaria which confers heavy metal tolerances to
diverse plant in diverse heavy metal soils. The genes which
are differentially expressed in AMF colonized tomato roots
are currently studied in our laboratory. The genus Thlaspi
(pennycress) of the Brassicaceae contains heavy metal
hyperaccumulating species. Some of them have now been
found to be strongly colonized by AMF. The fungi
colonizing Thlaspi in Nature have now been identified.
Many plants of salt marshes are also good mycorrhizal
plants. Up to 80% of all spores isolated from diverse saline
habitats in Germany and Hungary belong to one single
species, Glomus geosporum, as shown by molecular
characterization. The role of this fungus in conferring salt
resistance to plants will be discussed.
333 - Gene order evolution and paleopolyploidy in
hemiascomycete yeasts
S. Wong 1 , G. Butler 2 & K.H. Wolfe 1*
1 University of Dublin - Trinity College, Dept. of Genetics,
Dublin 2, Ireland. - 2 University College Dublin, Dept. of
Biochemistry, Dublin 4, Ireland. - E-mail: khwolfe@tcd.ie
The wealth of comparative genomics data from yeast
species allows the molecular evolution of these eukaryotes
to be studied in great detail. We used 'proximity plots' to
visualize gene order information from 14
hemiascomycetes, including the recent Génolevures
survey, to Saccharomyces cerevisiae. Contrary to the
original reports we find that the Génolevures data strongly
support the hypothesis that S. cerevisiae is a degenerate
polyploid. Using gene order information alone 70% of the
S. cerevisiae genome can be mapped into 'sister' regions
that tile together with almost no overlap. This map
confirms and extends the map of sister regions that we
constructed previously using duplicated genes, an
independent source of information. Combining gene order
and gene duplication data assigns essentially the whole
genome into sister regions, the largest gap being only 36
genes long. The 16 centromere regions of S. cerevisiae
form eight pairs, indicating that an ancestor with eight
chromosomes underwent complete doubling; alternatives
such as segmental duplications can be ruled out. Gene
arrangements in Kluyveromyces lactis and four other
species agree quantitatively with what would be expected if
they diverged from S. cerevisiae before its
polyploidization. In contrast, S. exiguus, S. servazzii and
Candida glabrata show higher levels of gene adjacency
conservation, and more cases of imperfect conservation,
suggesting that they split from the S. cerevisiae lineage
after polyploidization.
334 - A major role for gene duplication and gene loss in
the evolution of synteny and redundancy in yeast
G. Fischer * , I. Lafontaine, E. Talla & B. Dujon
Institut Pasteur, Structure and Dynamics of Genomes Dpt,
Génétique Moléculaire des Levures, 25 rue du Dr Roux,
75724 Paris cedex, France.
Based on Génolevures, a recent large-scale sequencing
program of 13 yeast species (FEBS Letter, special issue,
487(1), 2000), a comparative sequence study showed that
90% of the synteny breakpoints characterized between S.
cerevisiae and S. uvarum corresponded to micro-synteny
rearrangements. So, as little as 10% of all the synteny
breakpoints are attributable to gross rearrangements such as
reciprocal translocations. Micro-synteny breakpoints
resulted from ancestral duplications of one (or few) gene(s)
onto two different chromosomes followed by the
differential loss of the two copies between the two
genomes. In few cases, traces of the ancient presence of
one duplicate in the corresponding S. cerevisiae intergenic
Book of Abstracts 105