Botany 2004 "Alpine Diversity:
Adapted to the Peaks"
Snowbird Resort, Salt Lake City UT, July 31-Aug. 5, 2004
Symposium: After the book -
progress in parasitic plant research since Kuijt's Biology of
Parasitic Flowering Plants (1969)
The publication of Biology of Parasitic Flowering Plants by
Job Kuijt in 1969 marks the beginning of modern research on parasitic
plants. Since that time remarkable progress has been made in our
understanding of the physiology, phylogeny, and structure of these
plants. Some are major constraints to food production especially
in the semi-arid tropics and progress in meaningful control measures
has lagged.
ABSTRACTS:
Bennett, Jonathan [1],
Mathews, Sarah [1].
Phytochrome evolution in Orobanchaceae.
The evolution of complete or partial heterotrophy in plants may
involve the evolution of new morphological features such as haustoria.
There may also be reduced selective pressure for the maintenance
of features associated with photosynthesis. Some developmental
processes mediated by phytochrome photoreceptors are altered in
parasitic plants. These include leaf and chloroplast development,
the expansion of cotyledons and the expression of photosynthetic
genes. Orobanchaceae contains holoparasitic species, which produce
highly reduced leaves, and remain non-photosynthetic throughout
their life cycle, and hemiparasitic species, which produce leaves
and photosynthesize for some or all of their life cycle. The family
thus offers a system in which to investigate how the functions
of phytochromes might be altered in parasitic plants. We have
used DNA sequences of PHYA, the gene encoding one of the
four phytochromes that are widely distributed in angiosperms,
to infer a well-supported phylogeny for the family. Our sampling
includes for the first time representatives of Nesogenes
and Xylocalyx from Africa, which are nested within Orobanchaceae.
The robust gene phylogeny suggests that at least some hemiparasites
and holoparasites have two copies of PHYA and that some
PHYA genes harbor novel introns. We also have found evidence
that PHYA sequences are evolving under relaxed constraints
and we are investigating patterns of molecular evolution in more
detail to determine whether selective pressures change along branches
to major clades or whether they might be closely correlated with
shifts in habit.
------------------------------------------------------------------------
1 - Harvard University, Arnold Arboretum, 22 Divinity Avenue,
Cambridge, MA, 02138, USA
Keywords:
phytochrome, Orobanchaceae, molecular evolution.
Abstract ID:238
Blarer, Albert [1],
Bänziger, Hans [2], Endress, Peter K. [1], Anderson, Frank
[3], Nickrent, Daniel L. [4].
Rafflesiales problems and advances in research.
The group of holoparasites that include the spectacular Rafflesia
has been traditionally classified either as a single family (Rafflesiaceae
s. lat.) composed of two subfamilies and four tribes or as an
order (Rafflesiales) with four families (Rafflesiaceae s. str.,
Cytinaceae, Apodanthaceae, and Mitrastemonaceae). Moreover, Hydnoraceae
and Rafflesiales have been suggested, via most traditional classifications,
to be close relatives. In contrast, recent molecular phylogenetic
analyses, using nuclear, mitochondrial, and chloroplast genes
and thorough taxon sampling, show that Hydnoraceae are not related
to the remaining Rafflesiales but are a component of Piperales.
Analyses of nuclear SSU rDNA sequences placed a monophyletic Rafflesiales
among the eudicots, specifically within Malvales. This result
was compatible to previous work using mitochondrial genes wherein
Cytinaceae was shown to be related to Malvales. In addition, Apodanthaceae
shares a number of floral structural features with Malvales. In
contrast, an association with Malvales was not seen in a recent
molecular phylogenetic analysis using the mitochondrial gene matR
where Rafflesia and Rhizanthes were shown to be
a part of Malpighiales and Mitrastema was a component of
Ericales. We have conducted extensive molecular phylogenetic analyses
using nuclear and mitochondrial genes and, in contrast to previous
work, have attained complete generic sampling within Rafflesiales.
Our results indicate that mitochondrial gene trees are being influenced
by horizontal gene transfer events, thus compromising their utility
as phylogenetic markers.
------------------------------------------------------------------------
1 - University of Zurich, Institute of Systematic Botany, Zurich,
CH-8008, Switzerland
2 - Chiang Mai University, Department of Entomology, Faculty of
Agriculture, Chiang Mai, 50200, Thailand
3 - Southern Illinois University, Department of Zoology, Carbondale,
Illinois, 62901-6509, USA
4 - Southern Illinois University, Department of Plant Biology,
1125 Lincoln Drive, Carbondale, Illinois, 62901-6509, USA
Keywords:
parasitic plants, Rafflesiaceae, horizontal gene transfer, matR,
phylogeny, nuclear genes, mitochondrial genes, chloroplast genes.
Abstract ID:492
After the book - progress in parasitic plant research since Kuijt's
Holzapfel, Avi Sebastian [1].
Biology and Conservation of the New Zealand endemic
parasitic plant Dactylanthus taylorii Hook f. (Balanophoraceae).
Dactylanthus taylorii Hook f. (Balanophoraceae) is an endangered
holoparasitic plant endemic to New Zealand, parasitising roots
of native tree and shrub species. It is pollinated by an endemic
bat and introduced rodents. The morphology of the female flower
is described and shown to be similar to most other Balanophoraceae,
highlighting confusion in the literature about the female structures
in the family. Development of the endosperm and embryo, germination
and initial infection stages are shown for the first time. Contrary
to most literature oún holoparasitic plants, seeds of D.
taylorii can germinate in the absence of a host and it is
argued that this might also be true for other Balanophoraceae.
The species is furthermore able to reproduce vegetatively through
1-2 mm long infectious roots which are morphologically and functionally
similar to the radicle. Recent studies of genetic diversity point
to geographic and genetic isolation of populations as a natural
character of Dactylanthus rather than being caused by anthropogenic
factors. Conservation efforts are coordinated by a national recovery
group and their effect to date is summarized. The main threat
for the species is considered to be reproductive failure caused
by browsing of flowers and fruits through introduced mammals,
including rats and mice. The dual role of these rodents as pollinators
and browsers and the implications for conservation management
of D. taylorii are discussed. In a current seeding trial
flowering plants were first observed four years after sowing and
raise the prospect of establishing new populations as a conservation
management technique. The sex ratio of newly established plants
differs significantly from that of older populations. This finding
is discussed in regards to determination and stability of sex
in the seemingly dioecious species.
------------------------------------------------------------------------
Related Links:
Abstract of publication in Englera 22
1 - New Zealand Department of Conservation, Private Bag 3072,
Hamilton, 2001, New Zealand
Keywords:
Parasitic plant, conservation, Dactylanthus taylorii, Balanophoraceae,
germination, infection, rodent browse, reproductive failure, genetic
diversity
reproductive morphology.
Abstract ID:200
Abstract Detail
After the book - progress in parasitic plant research since Kuijt's
Kuijt, Job [1], Lye,
David [1].
The return of the isophasic filaments the early Arceuthobium
endophyte.
The isophasic (systemic) behaviour of some Arceuthobium species
involves a synchronized growth pattern which has a relatively
unknown endophyte component. We report the distribution of such
an endophyte of A. douglasii as present in the undifferentiated
part of the apical bud of Douglas fir (Pseudotsuga menziesii).
A method was developed to create a map of the parasite within
infected apical buds. Semi-thin serial sections of infected buds
were stained and photographed. The micrographs were analyzed,
the endophyte identified, and a simple animation created. This
animation revealed a highly organized relationship between parasite
and host, an important step in understanding this complex association.
------------------------------------------------------------------------
1 - University of Victoria, Department of Biology, PO BOX 3020
STN. CSC., VICTORIA, BC, V8W 3N5, CANADA
Keywords:
Arceuthobium douglasii, Douglas fir, apical buds, endophyte.
Abstract ID:246
After the book - progress in parasitic plant research since Kuijt's
Maass, Erika [2], Musselman,
Lytton John [1], Boles, Sandra [1].
Hydnora - The Ingenious Genus.
The Hydnoraceae is a family of holoparasitic root parasites, poorly
studied mainly because of their furtive nature. They spend most
of their life beneath the soil. The only parts of the plants that
develop above the soil surface are flowers. Hydnora triceps
is the only known dicot with hypogeous flowering. The successful
subterranean existence of Hydnora is made possible through
a variety of adaptations, most of which are not yet fully understood.
Three of the four currently recognized species occur in Namibia.
Various aspects of the biology of these three species, ( H.
africana, H. triceps and H.abyssinica) were studied
over a period of four years. Based on field observations and DNA
studies, a remarkable story about the natural history of Hydnora
is beginning to unfold. While little is known about pollination
strategies, studies on floral development strongly indicate that
the flowers are dichogamous, especially in the case of H. africana
and H. triceps. The opening in the center of the antheral
ring that allows entrance to the female part of the flower constricts
after pollen shedding, thereby preventing pollinators from reaching
the stigma. This seems to be less pronounced in H.abyssinica
where the antheral ring stays open. As is the case with other
holoparasitic root parasites, dormancy mechanisms prevent seed
germination in the absence of a host root. While no information
exists on seed dispersal, field observations indicate that small
mammals are involved. The way in which the parasitic seeds are
brought into close contact with the roots of the host remains
a mystery.
------------------------------------------------------------------------
Related Links:
Hydnora web site
The Parasitic Plant Connection
1 - Old Dominion University, Department of Biological Sciences,
Norfolk, Virginia, 23529-0266, USA
2 - University of Namibia, Department of Biology, Private Bag
13301, Windhoek, , Namibia
Keywords:
holoparasite , Euphorbia, Floral biology, hypogeous flowering,
seed germination.
Abstract ID:533
After the book - progress in parasitic plant research since Kuijt's
Malécot, Valéry
[1].
Biogeography of Olacaceae - paleobotanical and phylogenetic
congruence.
Olacaceae is commonly regarded as the most primitive family among
Santalales, the largest order of woody angiosperms. This family
was assumed to originate during late Cretaceous, as several tribes
show disjunct pantropical distributions, in agreement with an
early differentiation before the separation of the continents
in the Late Cretaceous. Morphological and molecular phylogenetic
studies, as well as a comprehensive survey of fossil material
(pollen fossil genus Anacolosidites) allows us to propose
an 80 million year long biogeographic history compatible with
tectonic and climatic changes. Current and fossil data show that
members of tribe Anacoloseae have always existed in regions with
tropical or paratropical climates. This hypothesis, also applicable
to other tribes, allows us to propose that the present pantropical
distribution is the result of splitting of climatic areas, a concept
similar to Wolfe's boreotropical hypothesis on the origin of tropical
floras. A preliminary survey suggest that this scheme may also
be applicable to some other Santalales and other tropical families.
------------------------------------------------------------------------
1 - Institut National d'Horticulture, UMR A 462 & Dept. Sciences
Biologiques, 2 rue le Notre, Angers, 49000, France
Keywords:
18S rDNA, 26S rDNA, matK, rbcL, biogeography, paleopalynology,
paleobotany, phylogeny reconstruction, Santalales, Olacaceae,
Anacolosidites, dispersal and vicariance
boreotropical hypothesis.
Abstract ID:802
McNeal, Joel R. [2],
Boore, Jeffrey L. [1], Kuehl, Jennifer [1], dePamphilis, Claude
W. [2].
Evidence for photosynthetic potential across the parasitic
plant genus Cuscuta using complete plastid genome sequences.
The genus Cuscuta (dodders) contains more than 150 species
of epiphytic vines that are obligate parasites on the stems of
a wide diversity of host plants, with a number of species commonly
becoming agricultural pests. Although all or most Cuscuta
species have long been considered to be nonphotosynthetic holoparasites,
there is a wide range of chlorophyll content and thylakoid structure
across the genus. Practically all species produce some chlorophyll
at certain life-stages or in certain specific tissues, although
leaves are reduced to minute scales in all species. For this study,
we sequenced the entire plastid genomes of two distantly related
species of Cuscuta that represent the opposite ends of
the spectrum for chlorophyll content and plastid structure in
the genus. Selected genes were also sequenced for various other
Cuscuta species representing systematically intermediate
lineages. In addition, the full plastid genome sequence of Ipomoea
purpurea (Morning Glory) was sequenced as an outgroup and
to determine which alterations to the plastid genome may have
predated the evolution of parasitism. Results indicate that most
species of Cuscuta probably are photosynthetic to a degree
despite the fact that many lack genes and promoters for plastid-encoded
polymerase. Patterns of selection, gene loss, and gene content,
as well as the implications of photosynthesizing with a streamlined
plastid genome, will be discussed in a phylogenetic context.
------------------------------------------------------------------------
1 - DOE Joint Genome Institute, 2800 Mitchell Drive, Walnut Creek,
California, 94598, USA
2 - Pennsylvania State University, Department of Biology, 208
Mueller Lab, University Park, PA, 16802-5301, USA
Keywords:
Cuscuta, parasitic plants, plastid genome evolution, photosynthesis
Convolvulaceae.
Abstract ID:494
After the book - progress in parasitic plant research since Kuijt's
Musselman, Lytton John
[1].
Parasitic Weeds in World AgricultureThe Best of Times,
the Worst of Times.
On a world wide basis, the most serious parasitic weeds impacting
food production are: witchweeds, species of the genus Striga,
especially S. hermonthica; broomrapes, species of the genus
Orobanche; and dodder, species of Cuscuta. Witchweeds
are probably the most serious because they affect subsistence
crops in the Sahel where few grains can grow. Meaningful figures
on the extent of crop damage are lacking but losses can be locally
devastating. During the past forty years extraordinary progress
has been made in understanding the biology of parasitic weeds
including elucidation of the germination process and haustorial
initiation. These findings have little impact on the farmers affected
by parasitic weedsamong the poorest people on the globe.
The most frequent method of control remains hand weeding, a labor
intensive effort. Development agencies have emphasized the production
of host varieties which can tolerate parasitism but still produce
an acceptable crop yield as a control method. Considerable funds
have been expended to investigate different strategies including
herbicides, genetically modified hosts, crop rotations, and biocontrol--
among others. Yet the severity of the problem, particularly with
Striga in Africa, does not seem to be ameliorated. New
measures are needed including research to understand the evolution
of virulence and the development of virulent strains from indigenous
species. For real progress to be made, a multi disciplinary approach
is essential and with significant funding. At the least, a farm
or series of farms committed to research on parasitic weeds is
needed.
------------------------------------------------------------------------
1 - Old Dominion University, Department of Biological Sciences,
Norfolk, Virginia, 23529-0266, USA
Keywords:
development, Sahel, Striga, Orobanche, Cuscuta, parasitic weeds,
witchweeds, broomrapes, dodders.
Abstract ID:724
Nickrent, Daniel [1],
Der, Joshua [1].
Santalaceae: phylogeny, taxonomy, and biogeography.
Santalaceae s. l. (sandalwoods plus Viscaceae) are a monophyletic
group in Santalales that includes 44 genera and over 1000 species
of herbaceous and woody perennial hemiparasites. Trophic modes
encompass both root parasites and stem parasites (mistletoes).
Molecular phylogenetic studies of Santalaceae s. l. have been
conducted using nuclear small-subunit rDNA and chloroplast rbcL
and matK. In combination, these sequences provide strong
support for the following monophyletic groups: the Pyrularia
clade (6 genera), the Thesium clade (6 genera), the Santalum
clade (12 genera), the Amphorogyne clade (9 genera), and
the Viscum clade (6 genera). Less support is obtained for
a clade including Comandra (5 genera). Three monophyletic
groups within the Santalum clade are resolved: the Osyris
clade, the Anthobolus clade and the Antidaphne clade;
the latter clade corresponds to the previously named family Eremolepidaceae.
A number of morphological synapomorphies exist supporting the
above clades. Alternate taxonomic classifications for Santalaceae
s. l. that do or do not incorporate rank will be discussed. The
molecular phylogenetic data can also be used to address biogeographic
patterns. For example, the distributions of genera within the
Pyrularia and Santalum clades show replicated track
patterns with similar ages for trans-Atlantic (or trans-Pacific)
divergences, thus suggesting similar responses to major global
tectonic and climatic changes during the Cretaceous and Tertiary
periods.
------------------------------------------------------------------------
Related Links:
The Parasitic Plant Connection
1 - Southern Illinois University, Department of Plant Biology,
1125 Lincoln Drive, Carbondale, Illinois, 62901-6509, USA
Keywords:
26S rDNA, 18S rDNA, matK, rbcL, biogeography, Classification,
mistletoe, parasitic plants.
Abstract ID:645
After the book - progress in parasitic plant research since Kuijt's
Press, Malcolm C. [1].
Physiological traits of root hemiparasitic Orobanchaceae
(ex-Scrophulariaceae): implications for community structure and
function.
Parasitic angiosperms exhibit a number of distinct physiological
traits. Using root hemiparasitic members of the Orobanchaceae
(ex-Scrophulariaceae) as model group, these traits will be examined
and related to the impact of the parasites on community structure
and function. Key traits include the following: high transpiration
rates; competition with the host from nutrients and haustorial
metabolism of host-derived solutes; uptake of host-derived secondary
metabolites; dual autotrophic and heterotrophic carbon nutrition;
distinct carbohydrate biochemistry storage of polyols; high
nutrient concentrations in green leaf tissue and leaf litter;
and small (often hairless and non-mycorrhizal) roots. The implications
of these traits for a number of interactions will be considered,
including: between host and parasite; competition between host
and non-host angiosperms (species hierarchies); interactions between
angiosperms and soil microorganisms (including decomposition);
and interactions with higher trophic levels (herbivores and pollinators).
------------------------------------------------------------------------
1 - University of Sheffield, Department of Animal and Plant Sciences,
Sheffield, S10 2TN, UK
Keywords:
none specified
Abstract ID:886
Westwood, James [1].
Molecular Biology of Parasitism in Orobanche.
Among the most intriguing aspects of parasitic plant development
is the integration of the haustorium into the host root. For the
past several years we have been studying molecular aspects of
this process, beginning with the expression of host genes in response
to parasitism, and subsequent use of parasite-inducible promoters
to engineer parasite-resistant hosts. Analysis of host gene expression
following parasitism indicates that Orobanche triggers
the host to activate some defense responses more than others.
Specifically, Orobanche induces defenses associated with
the localized production of phytoalexins much more than those
associated with salicylic acid (SA) signaling, pathogenesis-related
(PR) proteins, and systemic acquired resistance. One strategy
for resistance has been to try to artificially stimulate these
SA-mediated defenses that are not normally activated by the parasite.
This was done by engineering components of a parasite-triggered
hypersensitive response (HR) in tobacco, which resulted in decreased
parasitism in transgenic plants as compared to non-transformed
controls. We have also taken a very different approach to engineering
resistance by using sarcotoxin IA, an antibacterial peptide. The
gene encoding this peptide was fused to a parasite-inducible promoter
and transformed into tobacco. The resulting transgenic plants
exhibited greater biomass accumulation and reduced levels of parasitism
as compared to non-transgenic plants when grown in Orobanche-inoculated
soil. Investigations into the mechanism of sarcotoxin toxicity
to the parasite have documented the host-to-parasite movement
of protein and macromolecules that are larger than sarcotoxin
IA (4 kDa). Studies such as these are expanding our understanding
of parasitic plant biology as we work toward the ultimate goal
of protecting crops from these devastating weeds.
------------------------------------------------------------------------
1 - Virginia Tech, Plant Pathology, Physiology and Weed Science,
410 Price Hall, Blacksburg, VA, 24061-0331, USA
Keywords:
Orobanche, Genetic engineering, Parasitic plant.
Abstract ID:282
Wolfe, Andrea D. [2],
Randle, Christopher P. [2], Steiner, Kim E. [1].
Phylogeny and biogeography of Orobanchaceae.
Orobanchaceae, as it is currently defined, includes all levels
of parasitic ability ranging from nonparasitic (Lindenbergia)
to facultative and obligate hemiparasites to obligate holoparasites.
Several genera are of economic importance as crop weeds and have
been studied by scientists interested in developing methods of
control, but most genera have not been studied in a comparative
framework. In this study we have used ITS sequence data to build
a phylogenetic framework with which to examine previous systematic
hypotheses of relationships among genera, and biogeographic hypotheses
of either a Cretaceous, Gondwanan or mid-Tertiary, Laurasian origin
of the family. A single-most parsimonious ITS tree was produced
from a combined data set of nucleotides and gap characters. Our
results support the current classification of Orobanchaceae and
a hypothesis of a mid-Tertiary, Laurasian origin of the family.
------------------------------------------------------------------------
1 - California Academy of Sciences, Botany, Golden Gate Park,
San Francisco, California, 94118, USA
2 - The Ohio State University, Depatment of Evolution, Ecology
and Organismal Biology, 318 W. 12th Ave., Columbus, Ohio, 43210-4321,
United States
Keywords:
biogeography, ITS, Orobanchaceae, Parasitic plant, phylogeny,
Scrophulariaceae.
Abstract ID:300
SIUC / College of Science / Parasitic Plant Connection
URL: http://www.parasiticplants.siu.edu/meetings/BotSoc2004.html
Last updated: 26-Dec-04 / dln