1985 - Mycological Society of America

40
relationship of these results to the life cycle and
the phylogeny of D. iridis will be discussed.
J.C. SILVER and D. PEKKALA. University of Toronto,
Scarborough Campus, 1265 Military Trail, West Hill,
Canada M1C 1A4. Environmentally induced alterations
in chromatin and protein synthesis in Achlya.
Cell stress such as heat shock, results in several
changes at both the cellular and the molecular levels
in both the oomycete Achlya ambisexualis and in the
zygmocyte Entomophthora aulicae. In both organisms a
characteristic set of "stress proteins" is induced
which can be found associated with specific cytoplasmic
and/or nuclear fractions. Interestingly, two of
the characteristic Achlya heat-shock proteins i.e.
the 74kD and the 86kD proteins appear similar to two
Achlya developmentally regulated nuclear proteins induced
by the steroid hormone antheridiol. In Achlya
heat-shock results in changes in chromatin structure
and in the sensitivity of Achlya chromatin to the
enzyme DNase I. The changes in chromatin structure
appear related to the increased histone phosphorylation
which accompanies heat-shock. Heat shock also
appears to alter the deposition of actin in Achlya.
For example, nuclei in heat-shocked cells contain
large bundles of parallel-oriented filaments and,
studies with NBD-phallocidin, an actin specific
stain, indicate that these intranuclear filaments
contain actin. With heat-shock, the dephosphorylation
of a major group of 30kD Achlya phosphoproteins was
noted. These proteins could be isolated from Achlya
ribosomes and appear analogous to mammalian ribosomal
protein S6. Changes in the phosphorylation of these
and other ribosome-associated proteins may be involved
in the changes observed in the rate of protein
synthesis during heat shock.
(Supported by grants from NSERC Canada to J.C.S.)
Silver, J. C., see Rrunt, S. A.
Silver, J. C., see Pekkala, D.
Simmons, C. A., see Kerwin, J. L., et. al.
Smol ich, B. D., see Taylor, J. W., et. a1 .
F. W. SPIEGEL, Department of Botany and Microbiology,
University of Arkansas, Fayetteville, AR 72701. The
obligately amoeboid cells of Eumycetozoa - evidence
for several unique evolutionary origins.
Several of the flagellate protostelids and the
myxomycetes have an obligately amoeboid state in the
life cycle which will not become flagellate when
placed in liquid. A well known example of such a
state is the plasmoddiun of myxomycetes. Among the
protostelids obligate amoebae may be plasmodia,
plurinucleate amoebae, or uninucleate amoebae. In
order to determine the phy1ogeneti.c significance of
this state of the life cycle, it Is necessary to
determine whether it is homologous for all members
of the group or if it has evolved independently
several times. Evidence for common origin would only
support data gathered on the flagellar apparatus and
mitosis of amoebo-flagellate cells; evidence for
separate origins would help to define some of the
major clades of Eumycetozoa. Ultrastructure of the
cytoskeleton and, in some cases, mitosis in the
obligate amebae of Cavostelium apophysatum,
Protosporangium articulatum, and Ceratiomyxella
tahitiensis suggests that the obligately amoeboid
state has evolved independently in each of these
species. The characters of these states of the life
cycle may now be used to identify relationships
between flagellate and non-flagellate Eumvcetozoa.
Supported by NSF grant BSR 83-07376
L. J. SPIELMAN and M. HUBBES. Faculty of Forestry,
University of Toronto, Toronto, Ont., Canada MSS 1Al.
Variation in virulence and isozyme patterns of
Septoria musiva, agent of Septoria canker of hybrid
poplar.
Septoria musiva Pk. causes a serious canker disease
in hybrid poplar plantations and nurseries in the
United States, but is insignificant in Ontario plantations
and nurseries planted with the same clones.
The objective of this study was to determine whether
genetic differences between the fungal populations
in Ontario and the U.S. could be responsible for the
low level of disease in Ontario. Isozyme patterns
and virulence on hybrid poplars were compared among
isolates of 5. musiva from 4 states in the U.S. and
5 locations in Ontario. Patterns of acid phosphatase,
alkaline phosphatase, hexokinase, peroxidase,
peptidase, and other enzymes, revealed a high level
of genetic variation but showed little regional
differentiation among isolates. IVhen inoculated
into hybrid poplar clones by placement of a mycelial
plug over a small wound in the stem, some isolates
varied in virulence depending on the clone, but
other isolates consistently showed either high or
low virulence. Isolates with high virulence originated
from both the U.S. and Ontario, and there was
no difference in the distribution of high and low
virulence among isolates from the two countries.
There was no correlation between isozyme patterns
and virulence. Based on these results, we conclude
that 2. musiva exhibits low regional variation in
genotypes, and that populations in Ontario are genetically
similar to populations in other poplargrowing
regions of North America.
Sriskantha, 4., see Wach, M. P., et. al.
Steiner, S., see Hu, F.-S, et. al.
Stempen, H., see Evans, R. C.
Strickland, R., see Pommerville, J., et. al.
Suryanarayana, K., see Thomas, D. des S.
Sussman, D. A., see Hammill, T. M., et. al.
J. B. SUTHE~ND. BioSource Institute and the Institute
of Wood Research, Michigan Technological University,
Houghton, MI 49931. Cellulase and B-glucosidase
regulation in Ischnoderma resinosum.
The white-rot fungus Ischnoderma resinosum, a member
of the Poly-ooraceae, was grown with various carbohydrates
in stationary liquid media. Extracellular
filter paper activity, carboxymethyl cellulase, and
8-glucosidase were determined by the 2,4-dinitrosalicylic
acid method. Filter paper activity and carboxymethyl
cellulase were higher in cultures grown on
carboxymethyl cellulose than on either xylan or D-
glucose. In succinate-grown cultures, the addition
of either D-cellobiose or carboxymethyl cellulose resulted
in the induction of carboxymethyl cellulase.
Cultures grown with carboxymethyl cellulose plus a
second carbohydrate were tested for catabolite repression
of cellulase activity. Both filter paper
activity and carboxymethyl cellulase were repressed
by D-xylose, L-arabinose, L-fucose, and D-glucuronic
acid. Carboxymethyl cellulase was also repressed by