Book of Abstracts (PDF) - International Mycological Association

IMC7 Friday August 16th Lectures
substantial oxygen conductance averaging about 7 x 10-10
m3 s-1 was observed. We conclude that the air pores
conduct oxygen into the gas space below the pigmented
mycelium of the colony, where the rhizomorphs - which
can also conduct oxygen - originate.
440 - Control of motility in tubular vacuole systems in
fungi
A.E. Ashford 1* , L. Cole 2 , D. Davies 1 & G. Hyde 1
1 University of New South Wales, Sydney NSW 2052,
Australia. - 2 The University of Sydney, NSW 2006,
Australia. - E-mail: a.ashford@unsw.edu.au
Tubular vacuole systems occur in mycorrhizal,
saprotrophic and pathogenic fungi. In an Australian
Pisolithus they consist of two distinct components: less
mobile large compartments linked to the plasma membrane
variously interconnected with motile tubular elements.
These systems are implicated in endosomal processing,
intra- and inter-cellular transport, storage, and enhanced
interaction with the cytoplasm. In mycorrhizal associations
they may facilitate transport of elements between nutrient
absorbing hyphal tips and the interface with the plant
partner. Recent evidence for and against this hypothesis
will be evaluated. Tubule formation is a widespread
phenomenon in organelle systems of eukaryote cells and
offers an alternative to transport via vesicles. Vacuolar
tubule formation is a regulated process that is modulated by
both external and internal conditions and in Pisolithus is
dependent on microtubules but apparently not on
filamentous actin. Results with other inhibitors support a
role for GTP-binding proteins in regulation of vacuolar
tubule formation and the data are consistent with
involvement of a dynamin-like GTPase.
441 - The use of genomic repeated sequences to
characterize arbuscular mycorrhizal fungi
D. van Tuinen * , A. Gollotte, C. Arnould, O. Chatagnier, S.
Gianinazzi & V. Gianinazzi-Pearson
UMR 1088 BBCE-IPM INRA/Burgundy University, CMSE-
INRA, BP 86510 21065 Dijon Cedex, France. - E-mail:
tuinen@epoisses.inra.fr
Arbuscular mycorrhizal fungi (Glomales) form a root
symbiosis with more than 80% of land plant families,
improving plant mineral uptake and general plant health.
The different arbuscular mycorrhizal fungal species which
have been described do not generally show host-plant
specificity, suggesting a great plasticity of the fungal
genome. To date, knowledge concerning genome
organization and structure in these fungi is poor, so
limiting the understanding of their biology at a molecular
level. It is however known that arbuscular mycorrhizal
fungi have a large genome size, and evidence points to the
presence of a high proportion of repeated sequences.
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Book of Abstracts
Phylogeny analyses and identification of arbuscular
mycorrhizal fungi has been based on ribosomal or nonribosomal
repeated sequences, and the former have been
used to show genome variability between nuclei of a same
fungal isolate. In order to improve knowledge about
genome organization in arbuscular mycorrhizal fungi,
different types of repeated sequences have been
characterized and their distribution in the fungal genome
analyzed. Sequences containing elements found in
transposons have been isolated, and their role in the
evolution of the genome of these fungi will be discussed.
Part of this work is supported by the European Project
GENOMYCA (QLK5-CT-2000-01319;
http://www.dijon.inra.fr/bbceipm/genomyca/).
442 - Vegetative incompatibility and genetic diversity
among geographically different isolates of Glomus
mosseae
C. Sbrana 1* , L. Avio 1 , P. Strani 2 , V. Rinaudo 2 & M.
Giovannetti 2
1 Istituto di Biologia e Biotecnologia Agraria C.N.R.,
Sezione di Pisa, Via del Borghetto 80, 56124 PISA, Italy. -
2 Dipartimento di Chimica e Biotecnologie Agrarie, Via del
Borghetto 80, 56124 PISA, Italy. - E-mail:
sbranac@agr.unipi.it
Population studies based on vegetative compatibility tests
revealed the occurrence of genetically different isolates and
of vegetative compatibility groups within the same fungal
species in pathogenic, saprophytic and ectomycorrhizal
fungi. Successful anastomoses occur widely between
hyphae belonging to different individually germinated
spores of the same isolate of arbuscular mycorrhizal (AM)
fungi, though nothing is known about mycelial
compatibility between conspecific isolates. We studied
mycelial compatibility between geographically different
isolates of the worldwide distributed AM fungal species
Glomus mosseae. Vegetative compatibility tests performed
on germlings belonging to the same isolate showed that all
isolates were capable of self-anastomosing, whereas no
anastomoses were detected in pairings between germlings
of different isolates. Microscopic examinations detected
hyphal incompatibility responses, consisting in apical wall
thickening, followed by protoplasm withdrawal and septa
formation, in hyphal swellings produced by the
approaching hypha on the surface of the contacted one. The
intraspecific genetic diversity of G. mosseae revealed by
vegetative compatibility tests was confirmed by total
protein profiles and ITS-RFLP profiles. Since AM fungi
lack a tractable genetic system, vegetative compatibility
tests may represent a powerful tool for the detection of
genetically different mycelia and for investigating
population structure of these obligate symbionts.