Inoculum 56(4) - Mycological Society of America

MSA ABSTRACTS
nal array to participate in telomere function and/or maintenance, possibly by regulating
expression of the RecQ helicase gene. Internal to the RecQ-associated repeat
region, each of the eleven ends possesses its own unique sequences which
tend to be gene-rich, with many of the genes being predicted to have roles in pathogenicity.
One chromosome end consists of the ~1.6 Mb ribosomal repeat array,
which is interrupted by an insertion of a LTR retrotransposon approximately 11
kb from the telomere. Finally, sequence analysis of de novo telomeres that arose
in culture have allowed us to explore mechanisms of telomere hypervariability,
much of which appears to be promoted by the numerous transposable elements
that frequent subtelomeric regions. These results suggest that localization of genes
to chromosome ends may provide a source of genetic variation in this fungus, and
thus contribute to pathogenic adaptation. contributed presentation
Richardson, Bryce A. 1,2 *, McDonald, Geral I. 1 , Zambino, Paul J. 1 , Klopfenstein,
Ned B. 1 and Kim, Mee-Sook 1 . 1 USDA Forest Service, Rocky Mtn. Research Station,
Moscow ID, USA, 2 Washington State University, Department of Plant
Pathology, Pullman WA, USA. brichardson02@fs.fed.us. First report of naturally
occurring Cronartium ribicola infections on Scrophulariaceous hosts in
North America.
Cronartium infections were discovered on Pedicularis racemosa, P.
bracteosa, Castilleja miniata, and Ca. rhexifolia in a mixed stand of whitebark
and western white pine in northern Idaho. Most pines in this stand have white pine
blister rust cankers caused by Cronartium ribicola. Cronartium coleosporioides
(stalactiform rust) also occurs in the region. DNA sequencing of the rDNA internal
transcribed spacer (ITS) was used to identify rust species from single telial
columns. Based on 27 informative ITS sites that differentiate the two rust species,
all five collections of P. racemosa infections were C. ribicola. For Ca. miniata,
each rust species had infected a different single collection. One collection of Ca.
rhexifola and two collections of P. bracteosa were infected by C. coleosporioides.
Subsequent artificial inoculations using aeciospores from whitebark pine cankers
produced uredinia and telia on potted Ca. miniata and P. racemosa, and on leaf
cuttings of Ribes nigrum. Telia of Pedicularis-infecting isolates grown on R. nigrum
generated infections on western white pine seedlings, confirming the isolates’
capacity to complete their lifecycle. Ongoing research aims to determine the
distribution C. ribicola infections on Scrophulariaceous hosts, their role in the epidemiology
of white pine blister rust, and genetic mechanisms involved in possible
host switching. poster
Riquelme, Meritxell* and Bartnicki-García, Salomón. Department of Microbiology,
Center for Scientific Research of Ensenada (CICESE), Km. 107 Ctra. Tijuana-Ensenada,
Baja California, México. e@cicese.mx. The role of the
Spitzenkörper in hyphal growth and branching: the restless Spitzenkörper.
Growing fungal hyphae exhibit at their apex a structure named the
“Spitzenkörper” (Spk), whose composition and function has intrigued fungal biologists
for decades. A dark phase structure by light microscopy, the Spk is a
highly dynamic body composed of at least two parts: a conspicuous cluster of secretory
vesicles and an inner core containing cytoskeletal components, ribosomes,
and uncharacterized amorphous material. Our phase-contrast video-microscopy
studies have confirmed qualitative and quantitatively earlier observations suggesting
that the presence, position, and behavior of the Spk determine growth rate,
growth direction, and morphology. Mutations and inhibitors affecting both the
microtubular and the actin cytoskeleton destabilize the Spk with a major impact
on hyphal growth and morphology. The hyphoid model for fungal morphogenesis
attributes to the Spk the function of a vesicle supply center, and as such, the
model can duplicate diverse hyphal morphogenetic processes. This model accounts
for the fate of vesicles migrating from the Spk to the plasma membrane; it
does not consider how vesicles arrive to the Spk. We are using molecular tools
and high-resolution live imaging (fluorescence and phase contrast microscopy) to
discern the actual paths of vesicle traffic from their synthesis sites to the plasma
membrane in growing hyphae of Neurospora crassa. To fully understand Spk
function we need to understand the mechanics and regulation of vesicle dynamics
along the various steps in the secretory pathway: 1) vesicle formation at Golgilike
cisternae, 2) incoming vesicle migration via microtubules, 3) vesicle collection
by the Spk, 4) outgoing vesicle migration from the Spk to the plasma
membrane via actin microfilaments, and 5) exocytosis. symposium presentation
Rogers, Jack D. 1 * and Ju, Yu-Ming 2 . 1 Department of Plant Pathology, Washington
State University, Pullman, WA 99164, USA, 2 Institute of Botany, Academia
Sinica, Nankang, Taipei, 11529 Taiwan. rogers@wsu.edu. The Xylariaceae
of the Hawaiian Islands.
Collections of xylariaceous fungi have been made on the major Hawaiian
Islands, except Lanai. The holdings of the Bishop Museum have been studied.
Many habitats and substrates have been examined at least once. In terms of
species numbers collected (not frequency of collection) the following genera are
noteworthy: Hypoxylon with 36 species (8 new to science and 5 probably endemic);
Xylaria with 45 species (6 new to science and 3 probably endemic);
Biscogniauxia with 5 species (1 new to science and 1 probably endemic); Nemania
with 5 species (1 new to science and 1 probably endemic); and Anthostomella
with ca. 9 species (1 new to science and 1 probably endemic), in part according
to Lu & Hyde. Other genera frequently collected include Daldinia and
50 Inoculum 56(4), August 2005
Kretzschmaria. Genus Ascovirgaria is new to science; its anamorph Virgaria
nigra has a cosmopolitan distribution. Examples of problems being pursued include:
does Pisonia sandwicensis, an endemic species, host the same leaf-inhabiting
Xylaria pisoniae as the endemic Pisonia brunoniana (?); does Acacia koa
host the same species as the introduced species, A. mearnsii (?). The origins of
some of the xylariaceous fungi that have colonized the Islands will be discussed.
A book dealing with the Xylariaceae of the Hawaiian Islands is contemplated.
symposium presentation
Rogers, Jack D. 1 and *Ju, Yu-Ming 2 . 1 Department of Plant Pathology, Washington
State University, Pullman, Washington 99164-6430, USA, 2 Institute of
Botany, Academia Sinica, Nankang, Taipei 115, Taiwan. yumingju@gate.sinica.edu.tw
Xylaria species on termite nests.
Xylaria arenicola, X. brasiliensis, X. escharoidea, X. furcata, X. nigripes, X.
piperiformis, and X. rhizomorpha represent ancient names of fungi known to inhabit
abandoned termite nests. We attempt to redescribe them and to reduce the
confusion among them. Xylaria tanganyikaensis and X. readeri, species that
might be associated with termite nests, are described. We describe a new variety,
X. furcata var. hirsuta, and discuss an unnamed fungus that probably represents a
new species. Photographs and a key are presented to facilitate the identification of
these taxa. poster
Romaine, C. Peter. Department of Plant Pathology, The Pennsylvania State University,
University Park, PA 16802, USA. cpr2@psu.edu. Pharming in Mushrooms.
The advent of a facile gene transfer method for the preeminent edible mushroom,
Agaricus bisporus, has created new vistas for the genetic enhancement of
this important crop, and now enables the exploration of this species as a biofactory
for the production of high-value biopharmaceuticals (antibodies, enzymes, vaccines,
etc.). While social concerns overshadowing the safety of genetically modified
organisms are certain to impede the introduction of transgenic mushrooms
grown for food, the use of transgenic strains in manufacturing biopharmaceuticals
will likely find immediate public acceptance, for the end product (i.e., cheaper and
safer drugs) would improve the quality of human life. Relative to other crops, the
mushroom represents an intriguingly unique platform for the production of biopharmaceuticals,
as an extraordinarily high biomass can be produced in a comparatively
short time under high confinement and containment. Moreover, unlike
therapeutic proteins derived from animal-based systems nowadays, mushroommade
protein drugs would not carry the risk of contamination by human
pathogens, such as viruses and prions. symposium presentation
Romberg, Megan K.* and Davis, R. Michael. Dept. of Plant Pathology, UC
Davis, Davis CA 95616, USA. mkromberg@ucdavis.edu. Characterization of
Fusarium solani f. sp. eumartii on potato and tomato in California.
The causal agent of a wilt and stem-end rot recently seen in fields of seed
potatoes in California was subsequently identified as Fusarium solani f. sp. eumartii.
Four conserved DNA sequences (the ribosomal DNA intergenic transcribed
spacer region, and the elongation factor 1-alpha, beta tubulin and alkaline
phosphatase genes) of six isolates of this F. solani were compared to five isolates
of F. solani from tomato fields with Foot Rot and found to be identical. Lycopersicon
has apparently not previously been reported as a host for F. solani f. sp. eumartii.
Comparison of the DNA sequences to other Fusarium spp. segregate this
group of isolates into a separate monophyletic group. However, nit mutant pairings
revealed that most of the tomato and potato isolates comprise separate
VCG’s, although one potato isolate paired with most of the tomato isolates. Cross
inoculation experiments were used to determine the infectivity of isolates from
different hosts on various solanaceous species. poster
Romberg, Megan K.* and Davis, R. Michael. Dept. of Plant Pathology, University
of California, Davis, Davis CA 95616, USA. mkromberg@ucdavis.edu.
Characterization of California isolates of Fusarium solani f. sp. eumartii.
The causal agent of a wilt and stem-end rot recently seen in fields of seed
potatoes in California was subsequently identified as Fusarium solani f. sp. eumartii.
Four conserved sequences (the ribosomal DNA intergenic transcribed
spacer region, and the elongation factor 1-alpha, beta-tubulin, and phosphate permase
genes) of six isolates of this Fusarium solani f. sp. eumartii were compared
to five isolates of F. solani from tomato fields with Foot Rot and found to be identical.
Lycopersicon sp. has apparently not previously been reported as a host for
F. solani f. sp. eumartii. Comparison of the gene sequences to other Fusarium
solani isolates segregate this group of isolates into a separate monophyletic group.
However, pairings of nitrate-non utilizing mutants revealed that most of the tomato
and potato isolates fall into separate VCG’s, although one potato isolate paired
with most of the tomato isolates. Cross inoculation experiments were used to determine
the infectivity of isolates from different hosts on various solanaceous
species. poster
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