Abstracts Dealing with Parasitic Angiosperms and Mycoheterotrophs
Botany 2011
St. Louis, Missouri USA

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Wolfe, Andrea [1]

Assessing the host range of Hyobanche (Orobanchaceae) using DNA forensics.

Hyobanche L. is a small genus of holoparasitic plants distributed across southern Africa. It is found in a variety of ecosystems ranging from coastal sand dunes to fynbos biomes, the Little and Great Karoos, and into the highlands Lesotho. Hyobanche is a root parasite with an unique system of secondary haustoria formed on the leaf bracts of the rhizomes, which can be quite an extensive system underground. Proximity to other plants is not a good indicator of the actual host plant being parasitized. To determine the host range for species of Hyobanche ca. 400 host roots attached to haustoria were collected and their DNA extracted. Accessions with amplifiable DNA were sequenced and matched to sequences deposited into Genbank or to sequences obtained from potential host plants collected in proximity to parasitic plants collected in the field. Hyobanche parasitizes a wide range of plant genera from Asteraceae, Goodeniaceae, Poaceae, and Thymelaeaceae, and multiple plant genera may be parasitized at the same time.
1 - Ohio State University, Department of Evolution, Ecology, and Organismal Biology, 318 W. 12th Avenue, Columbus, OH, 43210-1293, USA

Rodrigues, Anuar [1],
Colwell, Alison [2], Stefanovic, Sasa [3].

Phylogeny of the parasitic genus Conopholis (Orobanchaceae): Evidence from plastid and nuclear DNA sequences.

Little is known of the evolutionary relationships among populations and species of Conopholis, a small holoparasitic genus with reduced vegetative morphology. In the most recent taxonomic classification of this genus, Conopholis is described as having two species, C. americana and C. alpina. This classification is based on a combination of presence/absence of characters along with a number of quantitative traits. We conducted the first phylogenetic study of Conopholis designed to develop a resolved and well-supported multi-locus phylogenetic hypothesis for this genus. We analyzed plastid (trnfM-E intergenic spacer and clpP gene/introns) and nuclear (phyA intron 1) nucleotide sequence data using the neighbor-net, Bayesian, and parsimony approaches in addition to conducting tests of alternative hypotheses. Our data set contained populations from a wide taxonomic sampling covering its entire geographical range in North America. The results indicate that regardless of the data set used or phylogenetic methodology employed, none of our analyses lend support for the strict subdivision of the genus into the two currently recognized species. Instead, three distinct genetic clusters were recovered and indicates that reciprocal monophyly between the two currently accepted species has not yet been achieved. Conopholis alpina is paraphyletic and shows evidence of belonging to at least two separate lineages. The monophyly of C. americana was also not recovered; however, this possibility could not be rejected with confidence. These analyses recovered three distinct lineages indicating that there could be a minimum of three species within the genus. We anticipate that a fine-scale morphometric analysis of morphological features within Conopholis may reveal shared features that could further corroborate our molecular results.

1 - Univeristy of Toronto Mississauga, Biology, 3359 Mississauga Road North, Mississauga, ON, L5L 1C6, Canada
2 - Division of Biological Resources, Yosemite National Park, El Portal, CA, 95318, USA

Morawetz, Jeffery [1].

Haustorial structural diversity across parasitic Orobanchaceae.

Orobanchaceae present an ideal system for studying evolution of the parasitic habit in flowering plants: with a single origin of parasitism, the full range of trophic modes is represented, from non-parasites to facultative and obligate hemiparasites and holoparasites. This parasitic ability is conferred through an organ unique to parasitic plants: the haustorium. The Orobanchaceae are parasitic on the roots of their host plants through terminal and/or lateral haustoria that develop along the parasite's root system. Haustoria have a generalized internal structure, being composed of a vascular core, hyaline body, and endophyte, often with a bridge of xylem cells connecting the vasculature of host and parasite. Reports of phloem connections between host and parasite in Orobanchaceae are rare, and detailed comparative studies of haustorial structure within and across the main parasitic lineages of the family are lacking. Haustoria, representing four of five parasitic lineages within the family, were collected from plants excavated in the field, and were subsequently embedded in paraffin and plastic for structural examination. Xylem bridges were observed in all taxa examined. The proximity of parasite and host phloem, and the presence of parenchyma including transfer cells at the host-parasite interface were variable, and characteristics of these elements will be further discussed. What are the structural modifications involved in phloem-to-phloem transfer between the host and parasite in Orobanchaceae and does this include direct sieve element connections?
1 - Rancho Santa Ana Botanic Garden, 1500 North College Ave., Claremont, CA, 91711, USA

Wickett, Norman J [1], Honass, Loren [1], Wafula, Eric [2], Timko, Michael [3], Westwood, James [4], Yoder, John [5], de Pamphilis, Claude W [6].

Using stage specific cDNA sequencing to uncover the origin and evolution of parasitism in Orobanchaceae.

The Parasitic Plant Genome Project is a collaborative effort to use stage specific cDNA sequences to understand the genomic changes that led to, and resulted from, the acquisition of a parasitic life history in Orobanchaceae. Transcriptomes of three Orobanchaceae species that vary in their nutritional strategies were sequenced using both 454 and Illumina technologies: the facultative hemiparasite Triphysaria versicolor, the obligate hemiparasite Striga hermonthica, and the holoparasite Orobanche (Phelipanche) aegyptiaca. Within each species, transcriptomes were sequenced from multiple developmental stages from germinating seeds, to early attachment to host, to above-ground reproductive and vegetative tissues. Using this comparative framework, we are developing a set of genes that may play an important role in haustorium formation (a parasitic plant specific organ that is used to invade the host plant), host invasion, and nutrient acquisition. Additionally, these data are being used to test hypotheses of molecular evolution and to explore the history of polyploidy in this lineage.
1 - Penn State University, Biology, 403 Life Sciences Building, University Park, PA, 16802, USA
2 - Penn State University, Biology, 403 Life Science Building, University Park, PA, 16802, USA
3 - University of Virginia, Biology, Gilmer Hall 044, PO Box 400328 , Charlottesville, VA, 22904-4328, USA
4 - Virginia Tech, Plant Pathology, Physiology, and Weed Science, 401 Latham Hall (0390), Blacksburg, 24061, VA, USA
5 - University of California, Davis, Plant Sciences , Mail Drop 3 , 137 Asmundson Hall, Davis, CA, 95616, USA
6 - Pennsylvania State University, Department Of Biology, 101 LIFE SCIENCES BUILDING, UNIVERSITY PARK, PA, 16802, USA

Santalales - Viscaceae

Cannon, Brandi [1], Garrison, Jessica [1], Sopas, James [1], Verastegui, Timothy [1], Randle, Christopher [1].

Presentation, aroma, and flavor: Investigation of host cues in the orientation and establishment of Phoradendron serotinum (Viscaceae).

Obligate parasitic plants cannot survive without the influx of water and/or nutrients from host plants. Therefore, successful establishment of haustoria (vascular organs of penetration and transport) is necessary for the survival of an emerging seedling. Extensive studies have been performed on the effect of host cues on germination, orientation, and development of haustoria in root parasites. For root parasites, host cues must be transmitted through the rhizosphere and are largely chemical. Plants that are parasitic on the aboveground stems of host plants must be able to detect hosts in a much different milieu. Phoradendron serotinum (leafy mistletoe) is a water parasite of broadleaf trees. While P. serotinum parasitizes many different hosts across its range, populations are most often locally host specific, preferring a single host even when other hosts are available. The underlying cause of this pattern of host preference is unknown, and will remain so until host cues responsible for successful establishment of haustoria have been identified. In this study, we examined the effects of light cues, physiochemical cues associated with the host surface, and gaseous chemical cues on the viability, orientation, and successful establishment of emerging haustoria on host plants. Light and physiochemical cues associated with the host substrate had a significant effect on haustorial establishment. Gaseous cues had a significant positive effect on viability and orientation. This latter result was foreshadowed by a similar finding in the stem parasite Cuscuta, which responds to gaseous cues emitted by host plants.

Caraballo-Ortiz, Marcos [1], Carlo, Tomas [1].

Coevolution of American mistletoes with tree families. Poster

Mistletoes are obligate parasitic plants that depend on host trees for their establishment, growth, and mineral nutrition. Although mistletoes play an important ecological role in plant communities, little is known about the coevolution between mistletoes and their hosts. To determine if mistletoes are host specific (a measure of coevolution), we selected the two largest mistletoe families in America (Loranthaceae and Viscaceae) and assembled a database using thousands of parasitism records from herbarium specimens and the literature. Next, we compared the frequency of host parasitism among the most common tree families and genera present in the Americas. We found that mistletoe parasitism is not random across plant families, and although parasitism has been recorded in more than 100 tree families, mistletoes were significantly more frequent in families such as Leguminosae, Fagaceae, Malvaceae, Rutaceae, and Pinaceae. To gain insight in the level of host specificity, we performed a reciprocal transplant experiment in the field using mistletoes in the genus Dendropemon (Loranthaceae). We carried out the experiment in Northeastern Puerto Rico where two very similar Dendropemon species coexist in different host trees: D. bicolor in Tabebuia (Bignoniaceae) and D. caribaeus in Citharexylum (Verbenaceae). The results of the reciprocal transplant suggest that Dendropemon mistletoes are host specific. These data also suggest that the global pattern of coevolution between mistletoes and their hosts is influenced by the taxonomic identity and the local interactions of both the parasite and its host.
1 - Penn State University, 208 Mueller Lab, University Park, PA, 16802, USA


Braukmann, Thomas [1], Stefanovic, Sasa [1].

Comparative plastid genome evolution in mycoheterotrophic Ericaceae.

Heterotrophic plants exhibit a wide range of evolutionary degradation of photosynthetic ability and rely entirely or partially on their hosts to supply water and nutrients. These plants are divided into two distinct, but evolutionary artificial groups, parasitic and mycoheterotrophic plants. Haustorial parasitism has evolved at least 11 times independently and there are at least 10 independent origins of mycoheterotrophy in angiosperms. Each lineage represents an independent origin of heterotrophy and heterotrophs are not well characterized outside a few well-studied examples. Ericaceae, the heather family, is a large and diverse group of plants with elaborate symbiotic relationships with mycorrhizal fungi, including several mycoheterotrophic lineages. Grounded within a phylogenetic framework and broad taxonomic sampling, a comparative investigation of plastid genomes was conducted in the family usinga slot-blot Southern hybridization approach. This survey contained lineages within Ericaceae with different life histories and trophic levels, including multiple representatives from the hemi-mycoheterotrophic pyroloids and holo-mycoheterotrophic monotropoids. A number of fully photosynthetic (autotrophic) members were included to best represent the other major clades within Ericaceae. This survey used 55 probes derived from all categories of protein-coding genes typically found inthe plastomes of photosynthetic plants. Our results indicate that monotropoids exhibit extensive loss off genes relating to photosynthetic function and retain genes with possible function outside photosynthesis. Furthermore, hemi-mycoheterotrophic plants retain most genes relating to photosynthesis but are polymorphic for the plastid ndh genes. Our survey extends previous inferences that plastid gene losses occur prior to becoming holo-heterotrophic and that mycoheterotrophic Ericaceae exhibit gene losses similar in pattern to parasitic plants.
1 - University Of Toronto At Mississauga, Department Of Biology, 3359 Mississauga Rd N, Mississauga, ON, L5L 1C6, Canada

Bowler, Rebecca [1], Fredeen, Arthur [1], Massicotte, Hugues [1].

Investigation of carbon gain of autotrophic, mixotrophic and myco-heterotrophic species at three sites in north-central British Columbia.

Most terrestrial vascular plants rely to some degree on mycorrhizal fungi for obtaining mineral nutrition. A subset of these plants also rely on their mycorrhizal partner(s) for some (mixotrophy) or all/most (myco-heterotrophy) of their carbon. Many pyroloids (Pyroleae tribe of the Ericaceae family) and some green orchids (Orchidaceae) are mixotrophs. By contrast, leafless orchids of the genus Corallorhiza are thought to be exclusively myco-heterotrophic. We conducted a pilot project where we assessed the photosynthetic competence of autotrophic, mixotrophic and myco-heterotrophic species growing in sub-boreal forests of north-central British Columbia. Gas exchange properties of each species were non-destructively measured in situ at least once a month during the growing season (May to September) of 2011 using a portable gas exchange system (model LI-6400, LiCor Inc.). Individuals of these species were also replanted in the Enhanced Forestry Lab at UNBC for further analysis. After approximately one month of acclimation to non-forest light levels, light response curves of each sample were measured using the same methods as in situ measurements with the exception of an artificial light source. We will highlight the current implications of our results and our future plans for this study.
1 - University Of Northern British Columbia, Ecosystem Science And Management Program, 3333 University Way, Prince George, BC, V2N 4Z9, Canada

Broe, Michael [1], Freudenstein, John [1].

Monotropa hypopithys L. (Ericaceae) is a distinct genus with well-defined species segregates at the molecular level.

The Monotropoideae are a herbaceous, achlorophyllous subfamily of the Ericaceae, within which 12 species in 10 genera are currently recognized. Most species are endemic to North America, however two---Monotropa uniflora L. and Monotropa hypopithys L.---have a much wider distribution in the Americas and Eurasia. We performed an extensive sampling of monotropoids across N. America, and here present molecular evidence for a revised treatment of this group based on ITS1, ITS2 and 26S (approx. 1200 bp). While the two Monotropa have long been recognized as a single genus, the phylogeny we present strongly supports the recognition of two distinct genera. Hypopitys (M. hypopithys) forms a monophyletic group with Pityopus, while Monotropa sensu stricto (M. uniflora) forms a monophyletic assemblage with Monotropsis and Monotropastrum (Asia). Hypopitys and Monotropa are further separated by the intervening genera Allotropa and Hemitomes. Within Hypopitys itself species and sub-species have been erected and subsequently synonymized to a remarkable degree. Small recognized five species in N. America, while in the most recent monograph Wallace rejected all such distinctions, choosing to synonymize some 80 putative species, subspecies and varieties in the Americas and Europe, noting 'there are no segregates that yet warrant taxonomic recognition'. Our analysis reveals five geographically circumscribed clades of Hypopitys in N. America alone---although the pattern is only partially congruent with Small's analysis---as well as a distinct Eurasian clade. This contrasts markedly with Monotropa, which exhibits no such structure in N. America at this level of phylogenetic resolution.
1 - The Ohio State University Herbarium, Evolution, Ecology and Organismal Biology, 1315 Kinnear Rd, Columbus, OH, 43212, USA

SIUC / College of Science / Parasitic Plant Connection
URL: http://www.parasiticplants.siu.edu/meetings/Bot2011ParAbstracts.html
Last updated: 13-Sept-16 / dln