12.4.1. horizontal gene transfer in the evolution of plant
J. D. Palmer;
Indiana University, Bloomington, IN, United States.
I will first give a brief overview of the remarkable propensity of plant mitochondrial genomes to take up foreign DNA, from the chloroplast and nucleus via intracellular gene transfer and from other plant mitochondrial genomes via horizontal gene transfer. I will then focus on the latter topic, presenting recent work from my lab on the extent, frequency, functional consequences, and mechanisms of plant-to-plant horizontal transfer of mitochondrial genes. Special emphasis will be placed on the role of parasitism in horizontal transfer and on the basal angiosperm Amborella trichopoda, whose mitochondrial genome is exceptionally full of foreign genes, acquired from a wide range of angiosperm and moss donors. The implications - both negative and positive - of widespread horizontal gene transfer for the utility of plant mitochondrial genes as phylogenetic and chronological markers will be discussed.
12.4.3. Evolution of RNA editing sites and its impact on
phylogenetic signal in plant mitochondrial genes
Pennsylvania State University, University Park, PA, United States.
We present an analysis of sequence evolution and phylogenetic signal in three mitochondrial genes -cox1, matR, and atp1 - that we have sampled from diverse flowering plant species. Phylogenetic signals are present in these genes that are mostly congruent with chloroplast and nuclear gene phylogenies, and contribute to the resolution of challenging problems in angiosperm phylogeny including origins of parasitic angiosperms and the phylogenetic position of key basal lineages. Several noteworthy phenomena were observed, including horizontal capture of host plant DNA by parasitic plants and evidence of a chimeric atp1 gene containing a portion of a local host plant atp1 gene. Abrupt reversals of the editing status (Riveting) of all editing sites has occurred repeatedly, implying frequent retroprocessing and recombination events involving edited mitotranscripts. These processes could drive high rates of correlated sequence evolution at editing sites, creating processed paralogs and destabilizing traditional concepts of homology. The impact of RNA editing on phylogenetic analysis is examined to revisit predictions made in an earlier study.
12.9.3. Hydnoraceae and its systematic affinities with Piperales
D. L. Nickrent1, A. Blarer2;
1Southern Illinois University, Carbonale, IL, United States, 2Institute of Systematic Botany, Zurich, Switzerland.
In a previous investigation, the holoparasitic Hydnoraceae clade (Hydnora, Prosopanche) was placed within Piperales; however, its exact affinity remained unresolved. More recently, a data set of 6 genes (nuclear, chloroplast, mitochondrial) for three outgroup and 16 Piperales taxa was constructed. Branch and bound analysis gave one tree with relationships fully resolved for Piperaceae (5 genera) and Saururaceae (4 genera). In contrast, the Aristolochiaceae (4 genera), Lactoridaceae (Lactoris) and Hydnoraceae clades remained unresolved, even when faster-rate parasites were removed. Aristolochiaceae is composed of two strongly supported clades: Asarum plus Saruma (Asaroideae) and Aristolochia plus Thottea (Aristolochioideae). A sister relationship between Hydnoraceae and the latter received moderate bootstrap support. Morphological divergence and branch lengths on molecular trees indicate a comparatively high degree of evolutionary change in this group, thus we recognize four clades (families): Aristolochiaceae s. str., Hydnoraceae, Lactoridaceae, and Asaraceae.
P0479. Acquisition of root hemiparasitism and other life
history traits in Santalales
V. Malécot1, D. L. Nickrent2;
1UMR A 462 - Institut National d'Horticulture, Angers, France, 2Southern Illinois University, Carbondale, IL, United States.
Based on molecular analyses, we examined the acquisition of hemiparasitism in Santalales, particularly Olacaceae s.l. Mapping of life history characters on molecular cladograms suggests a single origin for an ancestral root hemiparasite that can be assumed to be one of two ecological types. The first is an undershrub with relatively small fruits. This type, likely occurring in a humid forest, is reminiscent of the extant genus Ptychopetalum. The second type is a small tree with relatively large fruits. This type likely occurred in dryer areas (e.g. margins of humid forests and savannas) and is reminiscent of the genus Ximenia. After the acquisition of root hemiparasitism in Olacaceae, additional trends include: the acquisition of accrescent structures around fruits, large tree habit (Ongokea), and hummingbird pollination (Chaunochiton). Other trends seen in Santalales include: five independent acquisitions of the mistletoe habit; several independent derivations of an herbaceous habit within Santalaceae; reduction in leaf size, venation and changes in phyllotaxy (Santalaceae and Loranthaceae); and pollination syndromes (Loranthaceae).
7.12.3. Gender in the mistletoe Loranthus europaeus
females work harder
G. Glatzel1, M. Popp2;
1Institute of Forest Ecology, Vienna, Austria, 2Department für Chemische Ökologie und Ökosystemforschung, University of Vienna, Vienna, Austria.
The mistletoe Loranthus europaeus is trioecious with small flowers, which is a rare exception among the Loranthaceae, which usually have brightly coloured, bird pollinated hermaphroditic flowers on the same plant. In L. europaeus the population of hermaphroditic plants is functionally male, as almost all flowers are shed once the pollen is spent and very view fruits develop. Male and female plants differ in their morphology and physiology. Male plants are more ortho geotrophic and stout and less pendulous than female plants. Water potential is lower in female plants when compared to male plants under the same conditions. Autumnal leaf abscission is significantly later in females. This indicates that female plants have to work harder to support fruit development and maturation. Foliar element analysis as well as stable isotope analysis is currently performed and the results will be presented at the congress.
P0269. Branches anatomy of Fraxinus uhdei (Wenzing)
Lingelsheim and Prunus persica Batsch. infected by Cladocolea
C. De la Paz Pérez Olvera, J. Ceja Romero;
Universidad Autónoma Metropolitana Iztapalapa, Div. C. B. S., Depto. de Biología, México, D. F., Mexico.
True mistletoes are parasitic flowering plants. Seeds are disseminated by birds and deposited on host plants reducing their growth. Samples of 5 branches of Fraxinus uhdei and Prunus persica were collected in Mexico City. Blocks of 1 cm3 were obtained. Slides with typical cuts of the infected zone and the healthy zone were made. The wood of the two species has ring porous, their vessels are solitary and radial multiples, vessels pits are alternate. Its perforation plates are simples, rays have 1 to 4 cells and are heterogeneous and present fibre tracheids. The vessels in P. persica have helical thickenings and the outline is angular and the axial parenchyma is scanty diffuse. In F. uhdei the vessel outline is rounded and the axial parenchyma is of many types. The wood of mistletoe present diffuse porous. Vessels are solitary and clusters with the outline rounded, with pits alternate and simple perforation plates, present vascular tracheid. The axial parenchyma is in bands, present fibre tracheids. Rays are heterogeneous with 1 to 4 series. Both parenchyma types have abundant starch. The host anatomy is modifing when mistletoe penetrates, forming abundant contents.
P0275. Germination of a Tropical Mistletoe, Cladocolea
loniceroides (Van Tieghem) Kuijt Loranthaceae
R. V. Cid1, J. G. Márquez1, M. Ponce1, M. E. Engleman2;
1Facultad de Ciencias, México, d.f., Mexico, 2Colegio de Posgraduados, Montecillo, Edo. México, Mexico.
This mistletoe grows as a hemiparasite on various trees that may have economic value for fruit, lumber or as ornamentals. The tree´s physiology may be affected so severely that it eventually dies. Many aspects of floral biology, germination and establishment have not been described for this plant. In this paper, we describe germination, penetration of the host, and establishment. Samples of mature fruits germinating and developing on the host were obtained. Standard Microtechnique, light and Scanning Electron Microscopy (SEM) are used. We describe results with microphotography. The fruit adheres to the host with viscin and mucilage, which originate in the middle layer of the fruit wall. A holdfast is formed during the germination. By means of haustorium and a penetration organ, the haustorium penetrates and becomes anchored in the xylem. A knowledge of these mechanisms of establishment may help devise methods of control of this mistletoe.
P1542. Haustorium type, endophytic system form and vegetative
reproduction in four Scurrula L. species
M. P. Devkota1, G. Glatzel2, C. Calvin3;
1Botany Department, Amrit Campus, Thamel, Kathmandu, Nepal, 2Institute of Forest Ecology, BOKU, Vienna, Austria, 3Department of Biology, Portland State University, Portland, OR, United States.
Epicortical roots (ER) occurred in all Scurrula species regardless of host or elevation. Primary and secondary haustoria evoked a wood-rose response by host. Wood-rose form varied between and within species. Primary haustorium structural differences allowed classification into (1) flanging endophyte, (2) flanging endophyte with radial shafts, and, (3) sinker endophyte. Scurrula elata and S. gracilifolia differed in haustorial form on different hosts, and S. elata had the widest host range due to its specific haustorial and endophytic system plasticity. Epicortical roots of Scurrula resembled those of other Old World species in origin, morphology and branching pattern, but differed from those of New World species. The formation of secondary haustoria and root-borne shoots by ERs was common, but their frequency varied depending on the age of the mistletoe and the length and vigour of epicortical roots.
P0775. Biogeography and phylogeny of the sandalwood genus
Santalum (Santalaceae) based on sequence data and morphology
D. T. Harbaugh, B. G. Baldwin;
University of California, Berkeley, CA, United States.
Phylogenetic analyses using a combination of morphological and sequence data (ITS, ETS, 3'trnK intron and trnG intron) from all currently recognized taxa in Santalum provide evidence for broadscale, historical biogeographic patterns in the genus. A wellsupported basal grade of taxa from Australia supports an origin of the genus on that continent. Multiple long-distance dispersal events must be postulated to account for the distribution of Santalum in India and the Pacific. As previously proposed, the Hawaiian species recently treated in sect. Hawaiiensia (S. ellipticum and S. paniculatum) are evidently more closely related to one another than to the other Hawaiian endemics, S. freycinetianum and S. haleakalae, recently treated in sect. Santalum and appear to have resulted from two independent colonization events to Hawaii. The lineage including S. freycinetianum and S. haleakalae also includes S. boninense from the Bonin Islands and S. insulare from French Polynesia, Cooks Islands, Henderson Island and the Marquesas Islands, which indicates that Hawaii may act as a source for dispersal to island groups in the South Pacific and the Western Pacific.
P2044. Novel ribosome inactivating proteins (RIPs) from
Himalayan Viscum album (L.)- potential biomolecules for
V. Mishra 1,2, R. S. Sharma3, S. Bilgrami2, M. Paramasivam2, S. Yadav 2, C. R. Babu1,3, T. P. Singh2;
1Department of Botany, University of Delhi, Delhi-110 007, India, 2Department of Biophysics, All India Institute of Medical Sciences, New Delhi-110 029, India, 3Centre for Environmental Management of Degraded Ecosystems, University of Delhi, Delhi-110 007, India.
Ribosome inactivating proteins (RIPs) of Viscum album constitute the active principle of traditional tumor therapy in Europe. Himalayan V. album populations showed high morphological diversity. To assess the prospecting potential of this wild resource, 4 novel isoforms of its RIP (HmRIP) were purified and characterized. HmRIP was stable to a broad range of temperature (0-65 °C) and pH (3-9). Unlike all other type II RIPs, HmRIP1, 2 and 4 showed unique sugar affinity for L-rhamnose, meso-inositol and L-arabinose besides the galactose. Amino acid sequence of HmRIP determined by cDNA cloning showed deletions at one of the two sugar-binding sites. Crystal structure of HmRIP-sugar complex determined by X-ray crystallography revealed a significantly different conformation of the 2y sugar-binding pocket. Due to deletion of two critical residues forming wall of the pocket, the site has become much broadened. Therefore the sugar binds in a significantly different manner. The recognition of the sugar chains present on the cell surface is the first step in biological activity therefore HmRIP with distinct sugar specificity has pharmacological significance.
P0478. Inflorescence morphology in Balanophoraceae: moving
in a twilight zone.
R. K. Eberwein;
Kärntner Botanikzentrum, Klagenfurt, Austria.
The pantropically distributed holo-and root-parasitic family Balanophoraceae has panicled, mostly spadiceous inflorescence types with a remarkable variety of different designs. Contrary to other authors, all inflorescences are initiated endogenously in subterranean globose or sometimes elongated tubers. Racemes (subfam. Mystropetaloideae, Helosidoideae and Balanophoroideae), double racemes (subfam. Dactylanthoideae and Lophophytoideae) and triple female racemes (subfam. Sarcophytoideae) can be found. In tribe Helosieae spadices are covered by a dense layer of hexagonal, umbrella like structures which could be identified as bracts (not secondary axes as discussed before), showing an up to now unknown and for leaves unusual developmental pathway of peltation. Balanophoroideae possess spadices without secondary branching (in tribe Langsdorffieae they are designed like Asteracean heads). Structures covering the spadix, formerly described as axes ("spadicelli"), turned out to be transformed bracts. But it is still unclear if these "spadicelli" originate from numerous individual bracts or few multiple splitted bracts.
13.8.1. Progress in Malpighiales phylogeny: new insights
from eight genes
K. J. Wurdack1, C. C. Davis2;
1Smithsonian Institution, Washington, DC, United States, 2Ecology and Evolutionary Biology, University of Michigan Herbarium, Ann Arbor, MI, United States.
Malpighiales include 29 families previously assigned to 13 different orders sensu Cronquist. While the monophyly of most families within the order has been established, interfamilial relationships are largely unclear. Our phylogenetic analyses of DNA sequence data from 8 genes (plastid atpB, matK, ndhF, and rbcL; nuclear 18S and PHYC; and, mitochondrial nad1B-C and matR) spanning nearly 120 malpighialean taxa is beginning to resolve many of the major subclades within the order. These data further support the recent addition of Rafflesiaceae s.s. and Centroplacus, exclusion of Peridiscaceae, sister relations of Elatinaceae+Malpighiaceae and Putranjivaceae+Lophopyxidaceae, and inclusion of Paradrypetes in Rhizophoraceae s.l. New findings show Podostemaceae apparently nested within Hypericaceae, and a well-supported sister relationship between Phyllanthaceae and Picrodendraceae. The implications of these new results for the evolution of morphological characters, the problems of horizontal gene transfer, and for biome evolution will be discussed.
1.7.1. Research on Orobanche: what do we know and
what should we get to know?
D. M. Joel;
Agricultural Research Organization, Ramat-Yishay, Israel.
Orobanche spp. (broomrapes) are parasitic plants that develop multicellular haustoria, which connect to the roots of various dicots. Their tiny seeds germinate only after perceiving a host stimulus. Some species are weedy and cause severe damage to agriculture. The globalization of these parasitic weeds, the evolution of new races, and the gradual increase in their virulence pose threat to many crops worldwide, while means to control them are scarce. Studies of key developmental mechanisms of the parasitic interaction, regarding germination, attachment, haustorium penetration and host resistance, are needed for the understanding of their evolution. Proteomics and genomics should provide data on the genes involved in host-parasite interaction. Manipulation of developmental and metabolic pathways, which are involved in the parasitic interaction in both host and parasite, may provide protection against parasitic weeds. New sources for resistance in host plants may also be developed, employing specific antibodies, gene silencing, local release of toxins, and false signals.
1.7.2. Molecular phylogenetics and taxonomy of Orobanche
G. M. Schneeweiss1, J. Park1, J. Manen2, A. Colwell3;
1Institute of Botany, Vienna, Austria, 2Conservatoire et Jardin Botaniques, Genéve, Switzerland, 3US Geological Survey, Seattle, WA, United States.
Phylogenetic analyses of DNA-sequence data have greatly changed our understanding of circumscription of Scrophulariaceae and allied families, e.g., Orobanchaceae, traditionally comprising exclusively holoparasitic taxa, now include both hemi- and holoparasitic members. In a similar way, recent molecular phylogenetic analyses suggest substantial re-definition of the genus Orobanche, which is the largest of the holoparasitic genera in Orobanchaceae. One group, with chromosome base number of x = 12, contains the each monophyletic sections Gymnocaulis, Myzorrhiza, and Trionychon. The second group, with chromosome base number of x = 19, contains Diphelypaea and O. sect. Orobanche, the latter again comprising three distinct lineages. The relationships between these two major groups and those to other genera are unclear. As already suggested by previous authors, recognition of the sections of Orobanche as separate genera would allow to better reflect the phylogenetic patterns in a taxonomic system.
1.7.3. Orobanche-host plant interactions: ecological
and physiological aspects
J. A. C. Verkleij;
Institute of Ecological Science, Amsterdam, The Netherlands.
Among the various Orobanche species, a large difference in host range exists from very small to extremely wide. Because the Orobanche lifecycle is highly specialized for parasitism, the first stages of host-parasitic interactions seemed to be essential in determining host specificity. Orobanche seed germination is dependent on several abiotic and biotic factors as shown in various ecological and physiological studies. Although this first stage can be considered as the most discriminating one in terms of host selection, the germination process is too complex to draw definitive conclusions. The next stages crucial for the development of Orobanche are haustorium initiation, host tissue penetration and physiological compatibility. Progress in understanding these processes have been made in recent years using host plantparasite model systems. After successful infection Orobanche relies completely on its host for the supply of both reduced carbon, nitrogen and also minerals. The response of the host to infection by the holoparasite can be explained by just source -sink relations and will be discussed with respect to other parasitic angiospermhost systems.
1.7.4. Predictive empirical modelling of Orobanche
life cycle and seed ecology
A. J. Murdoch1, E. Kebreab2;
1The University of Reading, Reading, United Kingdom, 2The University of Guelph, Guelph, ON, Canada.
Dormancy in Orobanche seeds is removed as a two-stage process. First, after shedding from the mother plant, populations of dry Orobanche seeds after-ripen (lose primary dormancy). Increasing the temperature results in a faster after-ripening rate of the seed population. The second stage - conditioning - occurs at water potentials close to full imbibition. The rate of conditioning in the seed population also increases with increase of temperature. Secondary or even tertiary processes may interfere with dormancy loss. For example, prolonging the conditioning period beyond about 21 days decreases the subsequent germination response due to a) induction of secondary dormancy and b) at temperatures over about 25°C, loss of viability. Germination of conditioned seeds depends on chemical stimulation from host's roots, temperature and water stress. The thermal time for germination is strongly affected by water potential. Non-linear probability models account for these processes and provide predictive empirical models to describe the germination behaviour of the seed population. The impact of these results is discussed for O. aegyptiaca parasitising tomato.
1.7.5. Population genetics in Orobanche species
Z. Satovic1, D. M. Joel2, D. Rubiales3, J. Cubero4, B. Roman5;
1Faculty of Agriculture, Zagreb, Croatia, 2Newe-Ya'ar Research Center, Agricultural Reserach Organization, Ramat-Yishay, Israel, 3IAS - CSIC, Cordoba, Spain, 4ETSIAM - UCO, Cordoba, Spain, 5IFAPA - CIFA, Cordoba, Spain.
The studies of population genetics of Orobanche species are of great importance since the understanding of the variability within and between pathogenic populations is essential if selection programmes need to target sources of resistance in different areas and suitable breeding strategies need to be developed. The use of morphological markers in Orobanche has been difficult because holoparasitism resulted in a reduced number of suitable characters even for taxonomical purposes. The distribution of genetic variation in O. aegyptiaca, O. crenata, O. cumana, O. foetida and O. ramosa populations has been reviewed based on available molecular marker data. It is shown that by using simple DNA marker systems (e.g. RAPDs and ISSRs) the intraspecific variability can be assessed and problematic issues such as the differentiation between botanical taxa, geographical differentiation, and host-differentiation can be addressed.
1.7.6. Evolution of Ty1-copia and
Ty3-gypsy retroelements in holoparasitic Orobanche
J. Park, G. M. Schneeweiss, H. Weiss-Schneeweiss;
Institute of Botany, University of Vienna, Vienna, Austria.
Retrotransposons (RTNs) are mobile genetic elements, which transpose via an RNA intermediate. The transposition of RTNs is replicative, i.e., the existing elements are not excised but the newly formed copies re-integrate into new positions in the host genome. This feature, among others, such as ubiquity and high copy number, renders RTNs excellent molecular markers. We amplified and sequenced rt gene of Ty1-copia and Ty3-gypsy RTNs (at least 20 clones for each RTN type) from 13 Orobanche accessions. These accessions are (i) the economically most important weeds O. aegyptiaca and O. ramosa of sect. Trionychon and O. cernua and O. crenata of sect. Orobanche, and (ii) one close wild relative of each of these four taxa. While in sect. Trionychon RTN diversity is higher with many small unique RTN families, fewer RTN families are found in sect. Orobanche, some of them comprising numerous and very similar rt sequences. This suggests that species in sect. Orobanche might have experienced a recent burst of RTN activity. Additionally, we found indication of horizontal gene transfer for Ty1-copia and Ty3-gypsy RTNs, both from sect. Trionychon to sect. Orobanche and vice versa.
1.7.7. Orobanche species as weeds and
their management in sustainable agriculture
D. Rubiales1, M. Fernández-Aparicio1, B. Román2, J. C. Sillero2, J. I. Cubero3;
1CSIC, Córdoba, Spain, 2IFAPA, Córdoba, Spain, 3UCO, Córdoba, Spain.
About 3500 flowering plant species have lost their autotrophic way of life during evolution and parasitise other plants in order to supply themselves with water and nutrients. They are more than a fascinating group of plants as a few of them are severe constraints to major crops. By far the most economically damaging parasitic weeds are members of the genera Striga (witchweeds) and Orobanche (broomrapes). The most damaging Orobanche species are O. crenata that causes huge damage to legume crops, O. cumana that threatens sunflower, O. ramosa that attacks potato, tobacco, tomato and hemp, and O. aegyptiaca has very severe effects on legumes and vegetables, but also other species might gain importance. The spread of these parasitic weeds, and the gradual increase in their virulence pose threat to many crops worldwide, while means to control them are scarce. In the present work we revise their importance and re-evaluate control methods in the light of recent developments in crop breeding and molecular genetics.
3.12.5. Nutrients and heavy metal transfer from soil to
the host-hemiparastic plant association Cistus-Odontites luteus
growing on mine spoils
C. Poschenrieder1, A. Lombini1, M. Llugany1, E. Dinelli2, J. Barcelo1;
1Universidad Autonoma de Barcelona, Bellaterra, Spain, 2Università di Bologna, Bologna, Italy.
Odontites luteus (former Scrophulareaceae) a hemiparasitic plant was found associated with Cistus species at mine sites in Italy (Cu mine) and Catalonia (Pb, Ba mine). Soil, root and shoot concentrations of selected mineral nutrients (Ca, Mg, K, Fe, S, Mn, Zn, and Cu) and of non-essential elements (Al, Cd, Pb, Ba, and Sr) were analysed in order to get a first picture on how the hemiparasitic nutrient adquisition strategy may influence the mobility of these elements. Cistus sp. restricted the root to shoot transport of Cu, Zn, Al and Pb. In O. luteus similar root and shoot concentrations of Cu and Zn suggest that in this hemiparasitic plant the transport was less hampered, probably due to a direct uptake of mobile metal species from either or both xylem and symplastic sites of the host. In contrast, mobility of Pb was restricted also in the hemiparasite. The host-hemiparasitic plant association may serve as a model system for future investigations on metal mobility as a function of metal speciation in plants. Acknowledgement: Supported by DGICYT (BFU2004-02237CO2- 01) and Plà Recerca Catalunya 2001 (SGR00200).
P1186. Host specialization in Orobanche foetida
M. M. Rojas1, D. Rubiales2, J. I. Cubero2, J. C. Sillero1;
1IFAPA-CIFA, Cordoba, Spain, 2IAS-CSIC, Cordoba, Spain.
Orobanche foetida is widely distributed in Mediterranean area on wild legume plants, but has not been reported on cultivated legume species, except on faba bean in Tunisia. A population of O. foetida collected on Astragalus lusitanicus in Spain and another population collected on faba bean in Tunisia were studied to compare the pathogenicity on faba bean. The Spanish population was no infective on faba bean and seeds were poorly stimulated by all faba bean accessions. However, a substantial proportion of geminated seeds were able to contact and start attachment of faba bean roots, although failed to get established due to a frequent hypersensitive like host root cells reaction. On the contrary, the Tunisian population was very infective on faba bean and seeds germinated profusely in all faba bean accessions, with a higher success in attachment to faba bean roots and almost null hypersensitive like reaction, resulting in a high establishment. Some genotypic variation in resistance was observed in faba bean germplasm. Resistance against O. crenata was not operative against O. foetida, with the exception of cv. Baraca, the most resistant to both species.
P1187. Evolution of phytochromes in parasitic Orobanchaceae
J. R. Bennett1, S. Mathews2;
1Natural History Museum, London, United Kingdom, 2Arnold Arboretum of Harvard University, Cambridge, MA, United States.
The evolution of heterotrophy in plants may involve the evolution of new morphological features such as haustoria, but there may also be reduced selective pressure for the maintenance of features associated with photosynthesis. Some developmental processes mediated by phytochrome photoreceptors, such as leaf and chloroplast development and the expression of photosynthetic genes are altered in parasitic plants. Orobanchaceae contains both holoparasitic and hemiparasitic species and so 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 phytochrome A, to infer a phylogeny for the family. The well-supported gene phylogeny suggests that at least some hemiparasites and holoparasites have two copies of PHYA and that some PHYA genes harbor novel introns. There is also 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.
P1188. Genetic diversity in two variants of Orobanche
gracilis Sm. [var. gracilis and
var. deludens (Beck) A. Pujadas] from different
regions of Spain
B. Roman1, R. Hernandez2, A. Pujadas2, J. Cubero2, D. Rubiales3, Z. Satovic4;
1IFAPA - CIFA, Cordoba, Spain, 2ETSIAM - UCO, Cordoba, Spain, 3IAS - CSIC, Cordoba, Spain, 4Faculty of Agriculture, Zagreb, Croatia.
The pattern of genetic variation among populations of two taxa of Orobanche gracilis Sm. [var. gracilis and var. deludens (Beck) A. Pujadas] from Northern and Southern Spain growing on different hosts was analysed using RAPD markers. The Dice's distance matrix was analyzed by UPGMA method and the resultant dendrogram clearly divided populations by region and botanical variety with the Southern populations being more differentiated among them in both cases (var. gracilis and var. deludens). Concerning O. gracilis var. deludens, the dendrogram has also shown host differentiation between populations growing on two different species, Ulex baeticus and Ulex parviflorus. A complementary analysis of principal coordinates (PCoA) confirmed these results. The analysis of molecular variance (AMOVA) indicated that the lowest level of differentiation was found among the Northern O. gracilis var. gracilis populations whereas in the case of O. gracilis var. deludens from the South most of the genetic diversity was attributable to differences among populations.
P1189. Hemiparasitism: a way station to holoparasitism or
an evolutionary stable strategy?
J. E. Armstrong;
Illinois State University, Normal, IL, United States.
Is hemiparasitism an evolutionary stable strategy (ESS) or just a way station on the road from autotrophy to holoparasitism? Studies on the obligate hemiparasite Pedicularis canadensis (Rhinanthaceae) suggest that in prairie communities where nutrients or water are very limiting factors, parasitism is an adaptation both for enhancing acquisition of nutrients, particularly nitrogen, and/or water and for enhancing photosynthesis, thus maintaining both systems. The presence of the hemiparasite even enhances species diversity by extracting a higher cost upon dominate species, like grasses, in comparison to ephemerals like shooting star, Dodecatheon meadia. This lousewort species also inhabits forest communities in eastern North America where the prairie model predicts increased gain via parasitism without enhancing photosynthesis. If so, the lousewort's photosynthetic potential should decline in forest communities shifting the balance toward holoparasitism.
P1190. Anatomical features of the stem structure in the
E. O. Korol`kova;
Moscow State Open Pedagogical University, Moscow, Russian Federation.
All the of Orobanchaceae are parasitic plants without chlorophyll. This family consists of nearly 225 species belonging to 16 genera. The anatomical structure of the stem sin 87 species of 13 genera has been studied. In connection with parasitic way of life this plants have very simple morphological structure. Their anatomical structure become more develop, especially their excretory system. There are two excretory mechanisms ( by the glandular hairs in Orobanche, and by the epidermal cells in Cistanche) were found. As the anatomical data on stem structure shown, the Orobanchaceae is a natural taxon that should not be regarded as subfamily Orobanchoideae of the family Scrophulariaceae. The taxonomic position of the genus Lathraea in Scrophulariaceae is confirmed, however, by its stem anatomy. The diagnostic value of some stem features of Orobanchaceae has been established. The sections of genera Orobanche and Cistanche are well distinguished by features of stem anatomical structure.
P1191. The Figwort Family (Scrophulariaceae Juss.) in Belarussian
M. A. Jus;
Belarussian State University, Minsk, Belarus.
Scrophulariaceae is one of the largest family of Angiosperm in the temperate areas of the North hemisphere. The objects of our investigation include aboriginal and synantropical components of Scrophulariaceae (incl. Orobanchaceae Vent.) in Belarus. The work comprises critical taxonomic revision of complex groups, nomenclatural, caryological, ecological and phytocoenological information about all species of Figwort family in this region, with an issue of 8 years work of the author, with field experiences and revision of more than 7 000 specimens of the herbaria KRAM, KW, LE, LECB, LW, LWS, MHA, MSK, MSKU, MW, WIR etc. The phytogeography of the Scrophulariaceae in this region is compared to the flora in other neighbour areas (Poland, Baltic countries, adjacent regions of the Ukraine and Russia). Among the main contributions in our work are also presented an analytical key for the identification of the taxa, dot maps of the distribution of the endangered, rare and critical species, as well as information about protection and sustainable use of representatives of the Figwort family in Belarus.
P1192. Phenetic analyses of morphological traits in the
Alectra sessiliflora complex (Orobanchaceae)
J. J. Morawetz, A. D. Wolfe;
The Ohio State University, Columbus, OH, United States.
Alectra (Orobanchaceae) is a genus of primarily hemiparasitic herbs. Alectra sessiliflora var. sessiliflora, var. senegalensis and var. monticola form a morphologically cohesive group with overlapping distributions throughout sub-Saharan Africa, and are characterized by sessile yellow flowers and a branching habit. Traditional characters used to distinguish varieties were stamen filament pubescence or calyx pubescence. These characters are degenerate, preventing confident placement of a single specimen within one variety. This difficulty suggests that the taxonomic delimitations may not be meaningful. A phenetic study was undertaken to determine if this complex is best treated as a single large polymorphic taxon, or as a series of similar yet discrete taxa. Seventeen morphological characters were examined on 134 operational taxonomic units (OTUs), and the data were analyzed using UPGMA, PCA and discriminant analyses. Discrete clusters were not identified by the analyses.
P0259. Cuscuta jalapensis parasite on Coffea arabica
in Veracruz, México
M. López-Curto1, C. Esquivel-Huesca1, D. Díaz-Pontones2, J. Márquez-Guzmán1;
1Facultad de Ciencias. Universidad Nacional Autónoma de México, Ciudad de México, Mexico, 2Ciencias de la Salud. Universidad Autónoma Metropolitana, Ciudad de México, Mexico.
Cuscuta jalapensis has been detected parasiting coffee bean plants in Coatepec, Mexico. It is widely known that this parasite affects productivity of different crops. Coffee culture is quite important in Mexico so we decided to search how Cuscuta stablishes in coffee plantations. How deeply goes the haustoria into the host. What about the enzimatic mechanism of penetration. We also studied the embryology of this plant; our goal was to study some aspects of the biology of Cuscuta jalapensis and its invasion strategies on coffee cultures. Samples in LRW resin were sliced 2µm width for light microscope observations; we observed haustoria at SEM and, we detected activity of peroxidase enzime in 8µm cryostat slices, Sigma Immunochemicals technique. This orange filiform herb invades coffee plants through herbs and shrubs, on suitable hosts develops haustoria that penetrates beyond vascular bundles reaching medula. We identify peroxidase enzime involved in the generation of an entry pathway. We found a high incidence of abortion and observe perennation and autoparasitism. The only way to avoid infestation is to cut off infested plants and eliminate herbs aside
P0606. Evolution of plastid genomes within the parasitic
flowering plant genus Cuscuta
K. Krause, S. Berg, K. Krupinska;
Institute of Botany, Kiel, Germany.
The holoparasitic plant genus Cuscuta comprises species with full photosynthetic capacity, and functional chloroplasts, achlorophyllous species and intermediate forms with restricted photosynthetic activity and degenerated chloroplasts. Compared to nonparasitic plants, extensive deletions have taken place in the plastid DNA of achlorophyllous species encompassing photosynthetic as well as regulative genes, while green species like C. reflexa have retained most of the plastid genome. Transcription of the C. reflexa ptDNA resembles that of nonparasitic higher plants regarding promoter structure and transcription patterns but shows marked differences in the steady state RNA profiles. In intermediate species, genes for the photosynthetic apparatus were retained while the rpo genes coding for the plastid-encoded RNA polymerase that is responsible for their transcription were lost. Concomitantly, adaptations within the plastid genome have occurred that enable transcription mediated exclusively by a nuclear-encoded plastid RNA polymerase. Thus, Cuscuta is an interesting model for the evolution of reduced organellar genomes.
P1411. Phylogeny and plastid genome evolution in the parasitic
genus Cuscuta (Convolvulaceae)
S. Stefanovic1, R. G. Olmstead2;
1University of Toronto at Mississauga, Mississauga, ON, Canada, 2University of Washington, Seattle, WA, United States.
Previous findings on plastid (pt) genome structural rearrangements in Cuscuta were attributed to its parasitic life style, but without rigorous phylogenetic framework. Long PCR approach was used to sequence nearly entire pt genome from poorly investigated subgenus Grammica in order to determine its size, structure, gene content, and synteny. This pt genome is compared to that of tobacco and corresponding regions from taxa in the other Cuscuta subgenera. When all known pt genome rearrangements in Convolvulaceae are considered in a molecular phylogenetic framework three categories of rearrangements in Cuscuta are revealed: plesiomorphic, autapomorphic, and synapomorphic. Many of the changes in Cuscuta, previously attributed to its parasitic mode of life are better explained either as plesiomorphic conditions within the family, i.e., conditions shared with the rest of the Convolvulaceae, or in most cases, autapomorphies of particular Cuscuta taxa, not shared with the rest of the species in the genus. The synapomorphic rearrangements are most likely to correlate with the parasitic lifestyle, because they represent changes found in Cuscuta exclusively.
P2535. Combating Noxious Exotic Weed Mikania micrantha
in the Field
M. Li1, B. Wang2, B. Liu2, P. Yu2, H. Yu2, X. Cheng2, Q. Zan3, Y. Wang2;
1National Key Laboratory of Biological Control, Sun Yatsen University, Guangzhou, China, 2National Key Laboratory of Biological Control, Sun Yatsen University, GUANGZHOU, China, 3Guangdong Neilingding Futian National Nature Reserve, Shenzhen, China.
Mikania micrantha is a noxious alien weeds with a slightly woody vine species belonging to Asteraceae. It was introduced to Hong Kong as early as 1884 and now spread far beyong Hong Kong. M. micrantha was able to use shrubs and small trees as its support and then smothered the supports with thick mantels of its shoots. Physical removal experiment showed that uprooting all the creeping stems completely was difficult. The remained creeping stems sprouted in a short time and some of the slashed stems revived under considerable precipitation and the effect could only maintain for several months. Sulfometuron methyl was an effective herbisde to kill the weed. Cuscuta campestris, a parasitic plant, was able to suppress of M. micrantha. No other species was found to be dead caused by C. campestris within the infected circle. Restructuring plant community with multi species planting was conduct. Regional, fast growing, broad canopy and tall tree were criteria for selecting plant species. Within two years, the canopy of the community became continuous and suppressed the underneath weed, especially M. micrantha, indicating the effectiveness of the restoration measurement.
SIUC / College of Science / Parasitic Plant Connection
Last updated: 31-Jul-05 / dln