Book of Abstracts (PDF) - International Mycological Association

IMC7 Main Congress Theme III: PATHOGENS AND NUISANCES, FOOD AND MEDICINE Posters
eryngii, Flammulina velutipes in Korea. The disease
always accompanied the presence of isometric virus
particles. Using purification procedures involving Tris-
EDTA buffer extraction, PEG-NaCl precipitation,
differential centrifugation, and equilibrium centrifugation
in CsCl gradient (1.585 g/cm3), we have obtained three
isometric viral particles, one of 27 and two of 34 nm in
diameter, with different densities from P. ostreatus and P.
eryngii. The 27 nm particle, denser than 34 nm particle,
encapsidated ssRNAs as its genome. There were two kinds
of lighter particles with the same size of 34 nm which
encapsidated dsRNA. Coomassie Brilliant Blue stained
polyacrylamide gel (12%) electrophoresis showed different
polypeptides of coat proteins of Mr 29, 71, and 62 kD in
viral coat proteins, respectively. These results
demonstrated that there are at least 3 different kinds of
isometrc viruses whose genomes were ssRNA or dsRNA in
P. ostreatus and P. eryngii. The Flammulina velutipes
harbored different spherical ssRNA viruses. In an attempt
to prove that the viral complex is the causative agent for
the disease symptoms we cured the viruses from diseased
spawn. The virus-cured spown formed normal mushroom
and recovered from the epidemic. Therefore, the
phenonena of mushroom malformation and reduced harvest
in the mushroom farms could be of viral nature.
923 - Comparison of the aflR gene sequences of strains
in Aspergillus section Flavi
G.-F. Yuan * , C.-Z. Lee & G.-Y. Liou
Food Industry Research and Development Institute, P. O.
Box 246, Hsinchu, Taiwan, R.O.C., Taiwan. - E-mail:
gfy@firdi.org.tw
Aflatoxins are polyketide-derived secondary metabolites
produced by Aspergillus parasiticus, A. flavus and A.
nomius. Human health and economic benefit are most
affected by the toxic effects of aflatoxins. The aflR gene is
a regulatory gene of aflatoxin biosynthesis and encodes a
protein containing a zinc cluster DNA binding motif.
Although A. oryzae and A. sojae, used in fermented food
and ingredient manufacture, never have a record of
producing aflatoxin, they have shown the presence of aflR
gene. In this study, 34 strains belong to the Aspergillus
section Flavi were examined and the aflR gene of 23
strains of these strains were successfully amplified and
sequenced. No PCR products of aflR were found in five
strains of A. sojae and six strains of A. oryzae, these results
suggest that the aflR gene might not exist or significantly
different in some strains of A. sojae and A. oryzae. The
sequenced aflR genes of the 23 strains have 96% similarity,
especially the zinc finger DNA-binding domain are highly
conserved. The aflR gene of A. sojae has conspicuous
character, an extra CTCATG fragment inserted and a C to
T transition change cause earlier termination of the
encoded AFLR protein. The differences between A.
parasiticus/A. sojae and A. flavus/A. oryzae were also
found in some bases of aflR gene. Although the aflR genes
have no obvious difference between A. flavus and A.
oryzae, some differences may exist in aflatoxin producing
and no producing strains.
278
Book of Abstracts
924 - Sixty-one alleles of the ALS7 open reading frame
in sixty-six Candida albicans strains: ALS7 is a
hypermutable contingency locus
N. Zhang 1 , A.L. Harrex 2 , B. Holland 3 , R.D. Cannon 2 & J.
Schmid 1*
1 IMBS,Massey University, Palmerston North, New
Zealand. - 2 Dept. of Oral Sciences and Orthodontics,
University of Otago, Dunedin, New Zealand. - 3 IFS,
Massey University, Palmerston North, New Zealand. - Email:
J.Schmid@massey.ac.nz
The Candida albicans ALS (agglutinin-like sequences)
family of genes encodes agglutinin-like proteins believed
to play a role in adherence of the yeast to endothelial and
epithelial cells and is discussed as a virulence factor of this
important fungal pathogen of humans. Using 66 C.
albicans isolates, representing the major phylogenetic
lineages in a worldwide collection of 266 infection-causing
isolates, we discovered >= sixty-one different alleles of the
ALS7 open reading frame. Differences between alleles were
largely caused by polymorphisms in two nonadjacent
repeats, the so-called tandem repeat domain (21 different
types occurred) and the so-called VASES domain (21
different types). C. albicans is diploid, and combinations of
ALS7 alleles generated >=50 different genotypes. All
alleles tested were expressed in human patients; parts of
some open reading frames were transcribed in both
directions. Isolates representing a more pathogenic generalpurpose
genotype cluster (Schmid et al., 1999,
Microbiology 145: 2405-2414) had a higher number of
tandem repeats than other strains; of the 21 types of
VASES region found, two were largely exclusive to these
strains, the remaining almost exclusive to non-cluster
strains. Our results suggest that ALS7 is a hypermutable
contingency locus, important for the success of C. albicans
as an opportunistic pathogen of humans.