PHYLOGENETIC AND MOLECULAR ANALYSIS OF PARASITIC SCROPHULARIACEAE AND OROBANCHACEAE. C. W. dePamphilis*, N. D. Young1, A. D. Wolfe2, and T. J. Barkman*, *Pennsylvania State Univ., University Park, PA 16802, 1Trinity Univ., San Antonio, TX 78212, 2Ohio State Univ., Columbus, OH 43210, USA
Parasitism has evolved many times in angiosperms, but only Scrophulariaceae (including Orobanchaceae) has members representing the full range of parasitic ability from facultative hemiparasites to nonphotosynthetic holoparasites. Phylogenetic analysis of multiple plastid genes gives strong evidence for the monophyly of parasitic Scrophulariaceae and Orobanchaceae, and a detailed hypothesis for the origin and evolution of parasitism in this group. All these parasites plus Lindenbergia (nonparasitic sister to the parasite clade) may be classified in an expanded Orobanchaceae. One origin of parasitism is strongly implied, but holoparasitism has evolved at least 5 times in this group. Plastid gene and genome evolution is remarkably diverse, including rapid structural evolution and large shifts in substitution rates, and retention or modification of genes for alternative function in nonphotosynthetic plants.
THE INVASIVE COXI INTRON IN ANGIOSPERMS IS TRANSMITTED VERTICALLY ANDHORIZONTALLY, AND IS CONCENTRATED IN PARASITIC PLANTS. H. B. Croom1, T. J. Barkman2, J. R. McNeal2, C. W. dePamphilis2, 1Univ. South, Sewanee, TN 37383, 2Penn State U., Univ. Park, PA 16802, USA
Although most seed plants lack any intron in the mitochondrial coxI gene, a group I intron, homologous with the mobile ai4 intron in yeast, occurs sporadically in angiosperms. PCR tests (>300 species) found the intron to be rare in basal angiosperms, monocots, and basal eudicots, but more common in Asteridae and Rosidae. We compared coxI exon trees with intron trees to test hypotheses of ancestral intron vs. recent intron acquisition(s) in angiosperms. Recent initial invasion(s), followed by vertical and many horizontal transmissions of the intron were inferred across distantly related angiosperm groups. Surprisingly, the intron is found in every independently-evolved (nonphotosynthetic) parasitic plant lineage. We are investigating the possibility of direct host-parasite or parasite-host intron transfer as a mechanism to explain some of the extreme horizontal gene flow shown by this unique parasitic DNA element.
MULTIPLE ORIGINS OF PARASITISM IN ANGIOSPERMS INFERRED WITH MITOCHONDRIAL COXI DNA SEQUENCES. T. J. Barkman1, H. B. Croom2, N. D. Young3, C. W. dePamphilis1, 1Penn. State U., Univ. Park, PA 16802, 2U. South, Sewanee, TN 37383, 3Trinity U., San Antonio, TX 78212, USA
Phylogenetic origins of parasitic angiosperm lineages have been difficult to study using DNA sequences because plastid genes and 18SrDNA may be lost or evolve at very rapid rates making inferences uncertain. We undertook a large-scale sequencing study of conserved mtDNA genes present in all plants regardless of photosynthetic status. CoxI sequences were obtained from every major lineage of angiosperm including most hemi- and holoparasites. Phylogenetic analysis unambiguously places 5 major parasitic groups within the context of angiosperm phylogeny. Three other parasitic lineages have uncertain placement, but we can reject previous hypotheses for their affinities. Relative rates of coxI evolution in the parasites are not greatly elevated, but accurate placement of all groups will require additional mtDNA sequences. To this end, we are accumulating atpA sequences to complement the coxI data.
POPULATION GENETICS OF BALANOPHORA HARLANDI, A DIOECIOUS, HOLOPARASITIC FLOWERING PLANT. M. Sun, K. C. Wong and H. Q. Zhang. University of Hong Kong, Hong Kong
Few population genetic studies have been conducted on parasitic angiosperms. Ten natural populations of Balanophora harlandi were studied. Compared to non-parasitic dioecious plants, allozyme variation was low at both population and species levels, but the extent of gene flow was consistent with the outcrossing system. Lack of allozyme polymorphism may lead to underestimation of genetic divergence among populations. High levelsof polymorphism and gene diversity exist at both RAPD and ISSR loci, and the pattern of population structure revealed by the two marker systems were concordant. Host availability/population size may influence genetic structure of parasitic plants through the effect on population size of parasites.
ANATOMICAL INVESTIGATIONS OF HACHETTEA AUSTROCALEDONICA BAILLON, NEO-CALEDONIAN REPRESENTATIVE OF THE HOLOPARASITE FAMILY BALANOPHORACEAE. Jean-Michel Groult1 & Jérôme Muntzinger2, 1Lab. Paléobot./paléoécol., 12 r. Cuvier, 75005 Paris, France. 2Lab. Botanique, BP A5, 98848 Noumea Cedex, Nouvelle-Calédonie. (permanent address : Lab. Phanérogamie, 16 r. Buffon, 75231 Paris Cedex 05, France
Hachettea is a monotypic, endemic genus growing on tree roots such as Metrosideros (Myrtaceae). The body of the plant is only constitued of a dark tuber on which emerge orange to yellow, club-shaped inflorescences. Preliminary studies of the interface between Hachettea and host show a *wood rose + type (i. e. wood disk) , as Dactylanthus taylori Hook. f., endemic Balanophoraceae from New-Zealand. Organization of tuber follows the same scheme in both case. Xylem of parasite and host are directly joined, but there is no interpenetration of tissues. Anatomy of flowering shoot is of the classical type in Dicotyledons although floral features are much reduced. Despite of minor characters (e. g. no vegetative reproduction in H. austrocaledonica) the anatomical evidences strongly support a close relationship of Hachettea and Dactylanthus and thus its inclusions in the subfamily Dactylanthoidae sensu Engler.
THE DISTRIBUTION AND CONSERVATION OF RAFFLESIA IN KINABALU: RECENT KNOWLEDGE AND FUTURE DIRECTION. Jamili Nais, Kinabalu Park, Sabah Parks Board, Sabah, Malaysia
Despite its fame, actual research work on Rafflesia is lacking. Some 83 Rafflesia sites are known in Sabah, of which 69 (80%) are found around Kinabalu area. Various data has been collected from these sites, for example site activity, phenology and reproductive ecology (Nais, 1992' 1997). However, some basic question has remained unanswered, among others, the population structure, the genetic exchange between neighboring population, and the co-evolution of Rafflesia with its host plants (13 species of Rafflesia in 7 species of Tetrastigma). Molecular work should be one of the future emphasis in Rafflesia research. On conservation front, much of the habitat of Rafflesia is devoid of any form of protection. In Sabah, of the total known Rafflesia sites, 41 sites (52%) are devoid of any protection, and 67% of site extinction were caused by shifting cultivation. Within the Kinabalu area, which probably has the most number of known Rafflesia sites in the world, the surrounding lowland areas has no legal protection. As such, conserving Rafflesia also involves working with the local indigenous communities. Our successful Sabah Rafflesia Conservation Incentive Scheme has demonstrated this, which could be a model for other regions where Rafflesia occurs.
PHYLOGENETIC ANALYSIS OF THE OLACACEAE BASED ON MORPHOLOGY. Valéry Malécot1 and Danielle Lobreau-Callen2 (1Institut d'écologie, CNRS-FR3, Paléobotanique and Paléoécologie, UPMC, 12 rue Cuvier, 75005 Paris, France, 2CNRS-EPHE, Phanérogamie, M.N.H.N., 16 rue Buffon, 75005 Paris, France.
The proposed phylogenetic analysis focuses on the Olacaceae, and six species of others Santalales orders. The Santalales are monophyletic and the Olacaceae polyphyletic, but the clades and the grades obtained are related to the main existing tribes and palynologic or anatomic groups, except for Chaunochiton and Ptychopetalum. A clade fits to most of the Olacoideae and a grade to the Anacolosoideae. Opilia and a clade including Schoepfioideae, Santalaceae and Loranthaceae fit between them. The parasitism is an apomorphic feature appearing occasionally in Anacolosoideae and permanently in Olacoideae, Schoepfioideae and other Santalales. The variations of the main features are discussed.
DEMONSTRATING PARASITISM IN THE TREE-MISTLETOE NUYTSIA. Ainsley Calladine1 and 2John S. Pate, Plant Sciences, 1James Cook University, 4811, Australia, Botany, 2The University of Western Australia, 6907
Nuytsia floribunda, is one of three monotypic genera of root hemiparasites in the mistletoe family Loranthaceae. Nuytsia roots are attached to those of a wide range of hosts covering extensive areas by their unique root-severing haustoria and extensive networks of underground rhizomes and roots. Development of the haustorial connection between roots of host and parasite is described including a proposed apoplastic pathway of host xylem solutes into the haustorial parent root. Significantly lower parasite xylem potentials provide a driving force for such solute flow and transfer of both labelled N and an unusual, naturally occurring amino acid from associated hosts is demonstrated. These effective nutrient gathering mechanisms allow Nuytsia to survive in the nutrient poor heathlands of SW Australia.
EVOLUTION IN THE AUSTRALIAN LORANTHACEOUS MISTLETOES. Ainsley Calladine and Michelle Waycott, Plant Sciences & TESAG, James Cook University, Australia.
The Loranthaceae are epiphytic parasites except three monotypic
genera of root parasites (Nuytsia, Atkinsonia and Gaiadendron)
among some 1000 species in the family. These three encompass a
range in habit, trees, shrub and liana, and have been considered
primitive in this family, two being
Australian endemics. The Australian mistletoe flora includes Gondwanan
and intrusive elements. The intrusive component is a recent arrival
from Malesia. The Gondwanan element contains relict temperate
Gondwanan taxa with various plesiomorphic character states and
derived tropical and arid Australian radiations. We use 18S rDNA
sequence data to infer phylogenetic relationships among the Australian
Loranthaceae investigating evolutionary trends among primitive
Gondwanan and intrusive elements and assumptions of primitive
status in terrestrial genera.
HOST SPECIES EFFECTS ON GROWTH, AMINO ACIDS, ORGANIC ACIDS AND SUGAR CONTENT OF SANTALUM ALBUM. A. M. Radomiljac2,1, J. A. McComb1, J. S. Pate3 and K. U. Tennakoon3, 1Murdoch University, W. Australia, 2Department of Conservation and Land Management, W. Australia, 3The University of Western Australia
Santalum album seedlings were grown as with Sesbania formosa, Acacia trachycarpa, A. ampliceps or Eucalyptus camaldulensis as hosts, or without a host. Sandal growth was greater and its root:shoot ratio lower when parasitising the legumes than the eucalypt. Haustoria number varied markedly between species. There was close similarity between sandal and the legume hosts in concentration and composition of xylem sap amino acids, but marked differences between the sandal and the eucalypt. Host xylem sap contained variable amounts of sucrose, fructose and glucose while the sandal sap was dominated by fructose. Organic acid composition of the sandals was unaffected by differences in the organic acids of hosts.Prof. Jen A. McComb.
ECOLOGICAL SIGNIFICANCE OF PIGMENT VARIATIONS IN MISTLETOES. *Leonidas Zambrano, *Nelson Rojas and **Bernardo Ramírez, *Departamento de Biología, Universidad del Cauca,Colombia **Departamento de Biología, Universidad de Nariño, Colombia
The plant pigments of mistletoes were quantified and flavonoids were isolated by using 2D paper chromatography. The higher concentration of chlorophyll corresponds to Dendrophthora clavata (Benth) Urb. and Orycthanthus spicatus (Jack). Cuscuta grandiflora (H.B.K) showed the minimum value of chlorophyll. Several flavonoids were encountered in plants localized between 1500 m and 3200 m in Phoradendron trianae (Eichler) and Orycthanthus spicatus (Jack). Eichler. Viscaceae shows the presence of acacetin and artemetin and thymonin in Viscaceae and Loranthaceae. In conclusion chlorophyll and carotenoids are correlated with plants that receive a higher irradiance and flavonoids that depend on irradiance, altitude and location on the host.
LIVING STRATEGIES OF MISTLETOES IN TAIWAN. Shau-Ting Chiu, National Museum of Natural Science, Taichung, Taiwan, R. O. C.
The mistletoes in Taiwan highly diversified, and the hosts species are also highly varied, ranging from gymnosperms, angiosperms, trees, shrubs and lianas, to even other mistletoes. Due to the close relationship between the dispersal of mistletoes and the diet of flowerpeckers, the distribution and the phenology of mistletoes are mutually affected. For example, Taxillus tsaii Chiu and T. rhododendricolus (Hayata) Danser. at different altitude flowers and bears fruits in varied periods. Two major dispersal agents appear in different seasons. Whether developing primary leaves as seed germination coincide with the invasion to the host bark also varied. It is suggested that the phenology, the dispersal and the seed germination in the life cycle of mistletoes are diverse because they have adapted to the different ecosystems with varying temperatures and lengths of the growing seasons.
FLORISTIC AND ECOLOGICAL ASPECTS OF MISTLETOE PLANTS FROM SOUTHWEST ANDEAN ZONE OF COLOMBIA. *Leonidas Zambrano, **Bernardo Ramírez and *Nelson Rojas, *Universidad del Cauca, Departamento de Biología, **Universidad de Nariño, Departamento de Biología. Popayán, Colombia
This study was conducted in the Andean Southwest of Colombia including some life zones of the West, and central mountains. The altitudinal range begins at 650 m, tropical dry forest (b-ST) and 3100 m (paramune zone). Viscaceae represents the widest distribution in life zones sampled. Loranthaceae were localized between 1650 m premountain humid forest (bh-PM) and 3100 m. Cuscutaceae was collected at 3100. Viscaceae and Loranthaceae were distributed in premountain wet forest (bmh-PM) as well. Hemiparasite plants colonize primary and secondary forests and agro-eco-systems, preferentially in woody plants. The economical importance of some genus is related to infections in fruit trees and crops.
FLORISTIC AND ECOLOGICAL ASPECTS OF ZONE MISTLETOE PLANTS FROM SOUTHWEST ANDEAN ZONE OF COLOMBIA. *Leonidas Zambrano P., **Bernardo Ramirez P. and *Nelson Rojas M. *Universidad del Cauca, Departamento de Biología, **Universidad de Nariño, Departamento de Biología, Popayán, Colombia
This study was conducted in the Andean Southwest of Colombia including some life zones of the West, and central mountains. The altitudinal range of the samples begins at 650 m altitude, tropical dry forest (b-ST) and 3100 m (paramune zone). Viscaceae represents the widest distribution in all life zones samples. Loranthaceae were localized between 1650 m premountain humid forest (bh-PM) and 3100 m (paramune zone). Cuscutaceae was collected at 3100 m (paramune zone). Viscaceae and Loranthaceae were distributed in premountain wet forest (bmh-PM) as well. Hemiparasite plants colonize primary and secondary forests and agro-eco-systems, preferentially parasiting woody spice plants. The economical importance of some genera such as Pthirusa, Phoradendron, Oryctanthus is related to infections in fruit trees and crops (Coffea, Manihot). Finally, some ecophysiological adaptations, are discussed.
PHYLOGENETIC RELATIONSHIPS IN PHORADENDREAE (VISCACEAE). I. MAJOR LINEAGES AND POLYPHYLY OF PHORADENDRON AND DENDROPHTHORA. Vanessa E. T. M. Ashworth, Rancho Santa Ana Botanic Garden and Claremont Graduate School, 1500 North College Avenue, Claremont, CA 91711-3157
The tribe Phoradendreae includes two genera, Phoradendron and Dendrophthora, that are morphologically very similar but differ in the number of locules per anther. Relationships within and between genera are unknown. This study addresses these issues using sequences from three regions of the nuclear ribosomal DNA (nrDNA) cistron. They are (1) the ITS region, (2) the D2 divergent domain and flanking sequences of the 26S nrDNA, and (3) the D8 divergent domain and flanks of the 26S nrDNA. Maximum parsimony analyses suggest that neither Phoradendron nor Dendrophthora is monophyletic. Three major clades were identified whose topologies suggest that characters traditionally used for primary subdivision are homoplastic.
TWO DISTINCT HOST RACES OF ARCEUTHOBIUM AMERICANUM. C. Jerome & B. Ford, Botany Dept, U. of Manitoba, R3T 2N2
The dwarf mistletoes (Arceuthobium spp.) comprise some 40 species of vascular plant parasites. Arceuthobium americanum infects 2 principal hosts, Pinus banksiana and P. contorta, and has the most extensive range of any N. American dwarf mistletoe. Surprisingly, A. americanum has been the subject of limited genetic and taxonomic research. Based on a lack of apparent morphological and phenological differences among populations, past researchers have found no evidence for undetected taxa. However, genetic differentiation seems likely due to the adaptation of A. americanum to different host populations over its extensive geographic range. We have used a new genetic tool, AFLP, to analyze the population structure of this species. Our preliminary findings suggest that A. americanum consists of two distinct genetic races, one that infects P. banksiana, and another that infects P. contorta.
CYTOCHEMISTRY AND ULTRASTRUCTURE OF THE VISCIN CELLS OF ARCEUTHOBIUM AMERICANUM (DWARF MISTLETOE). Cindy Ross and Michael J. Sumner, Department of Botany, University of Manitoba, Winnipeg MB R3T 2N2.
Arceuthobium americanum (dwarf mistletoe) is a parasitic plant. Its 'seed' lacks a seed coat, instead, the embryo and endosperm are enveloped by mucilaginous viscin cells. Viscin cells originate within the fruit as isodiametric cells which elongate as vacuoles accumulate at their distal ends. The endomembrane system produces a mucilage which passes though and is deposited outside of the primary cell wall. Cytochemistry reveals that the mucilage has a protein component and an insoluble carbohydrate component. The mucilage was probed with several lectins to determine a carbohydrate profile. Preliminary results indicate that galactose is the predominant mucilage carbohydrate. The mature, thickened viscin primary cell walls are helically-arranged, birefringent, and have a large cellulosic component.
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Last updated: 17-Mar-00 / dln